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UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT
STATION
a REPORT FOR THE FISCAL YEAR
ENDING JUNE 30th, 1916
MAY, 1917
CONTENTS
PAGE
LETTER OF TRANSMITTAL TO GOVERNOR OF FLORIDA ................................. 5R
BOARD OF CONTROL AND STATION STAFF--..................-...................--........-. 6R
LETTER OF TRANSMITTAL TO CHAIRMAN OF BOARD OF CONTROL................ 7R
Introduction ---...-- -- --.......... ------------......-- 7R
Lines of Work ..... ..... ................... ...... ........ 7R
Publications ----..... ---....- .......................-. 12R
REPORT OF AUDITOR......................... ........................ ........ .... ------- -13R
REPORT OF ANIMAL INDUSTRIALIST... ........ .....--- ..--. ..................... 14R
Dairy Herd ......----------------------..... ........................... 14R
Experiments Conducted with Herd---...........---.~...---. ............ ...... 18R
Japanese Cane.....------.. .. --....... -........--. --- ---- .................. 23R
Cowpeas, Yield of Forage and Grain...................... --.......--.... 24R
Velvet Beans .........---------....-- ................--... 25R
Cotton and Sorghum Yields................... --- .....-----..--- 26R
Replanting Japanese Cane......---..........--------.................... 26R
Sweet-Potato Fertilizer Test......................... ......... ..................... 28R
REPORT OF PLANT PHYSIOLOGIST............-...-.........--.... --- ....--- ...- 30R
Toxic Effect of Organic Chemicals on Citrus..........................---......-- 30R
Effect of Vanillin on Citrus Cuttings ...---........ .............. 36R
Injury to Citrus Trees by Ground Limestone............................... 38R
REPORT OF ENTOMOLOGISTI..-....-.----. .------ ------ ---. 51R
Velvet Bean Caterpillar............... ----- ...- ........ 51R
Florida Flower .Thrips- ----.......................... ...... ............................... 51R
Combating Nematodes by the Use of Calcium Cyanamide.......-....... 55R
Insects of the Year--------............ .................... 64R
REPORT OF PLANT PATHOLOGIST........................ ........ ------66R
Gummosis ..----......-------------........ .---------.66R
SMelanose ............-.. ..-----------------... 67R
Citrus Canker..... ------------...................---- .. 69R
SLightning Injury-... ............--..--......--.... ........--.. -. 74R
S Lemon Bro n Rot Fungus.............. ..... ................................... 78R
Citrus Diseases..---....--..--......-.......-- -------. ............. 79R
REPORT OF ASSOCIATE PLANT PATHOLOGIST......-..-.~------.-..........-..- 80R
Damping Off in the Seed Bed------.............................. 80R
Seed Disinfection...- -----... ---- ---.........--.--- ...... 86R
Buckeye Rot of Tomato Fruit...--...--. ..------- ........-.....-.., 88R
Some Bacterial Diseases of Vegetables_--.-- -----...... ............-- 89R
Other Diseases of Vegetables............................-------------.- --.----------- 0R
REPORT OF LABORATORY ASSISTANT IN PLANT PATHOLOG-------.................. 99R
Pecan Dieback ..................... .....-... .......-...... 99 R
Leaf Blight of the Fig-...-...---... ,--- ---- ... .... ..... -- 108R
\ REPORT OF CHEMIST.--... ----.......- --------- ...........-.------.- 113R
Citrus Experimental Grove ... ....--------....... ........... 1113R
Soil Tank Investigation.................. ...... .......................... 116R
Contents
BULLETIN 128.-CITRUS CANKER-III. PAGES 1-20.
Introduction ..........-----..- ----------...........
History of Citrus Canker .---............... ... ......... ...- .......
Distribution in Florida..-.................... ----... .. ...
Appearance of Citrus Canker............. -------- .... ..-...
Cause of Citrus Canker................................ ---.-
Laboratory Investigations.....--.. ...- --................... .... .......
Spread of the Disease........................ .. ..... .......--- .
Control ........................---------.......
BULLETIN 129.-JAPANESE CANE. PAGES 21-44.
Introduction ........... .........------- ...
Uses of Japanese Cane........... .
Soil for Japanese Cane............-.. ...
Saving Seed Cane............ .............. ..............
Preparation of Seed Bed ...... ---..... ...........-.. ..... .................
Cane for Planting.... ........... -..: .........--
Planting ........ --....-........ -.....-- ..
Cultivation ...-..........-.... ... ..- .......... .... ... ... .........
Harvesting ........ ................. ......... .......... --. ..
Japanese Cane and Velvet Beans..... ...... ...........
Fertilizer Experiment with Japanese Cane............... .......-.......
Storing Japanese Cane...................... .... . .......... .... ....
Replanting Japanese Cane................................- .. ... .
BULLETIN 130.-CONTROL OF THE VELVET BEAN CATERPILLAR. PAGES 45
Introduction ...................-... ... ...........................
Life History of the Insect.....................-......-.. ...........
Migration and Distribution. --........-- .... .. ............. ..... ..............
Food of the Caterpillar.................... ........... ....
Methods of Control................. ..........................
BULLETIN 131.-PIG FEEDING. PAGES 61-70.
Introduction ............................................ .................. .......
Experiment I: Corn, Green Cowpeas, Green Sorghum.............................
Experiment II: Corn, Peanuts, Rape............................ . .......
Experiment III: Corn, Rape, Velvet Beans........................----..
Experiment IV: Corn, Velvet Beans, Iron Sulphate ,..--.........................
Experiment V: Corn, Dasheens, Velvet Beans................................. .
PRESS BULLETINS
239.-Bulletins and Reports on Hand.
240.-Fertilizer Test of Sweet Potatoes.
241.-The Time of Ripening of Velvet-Bean Varieties.
242.-Feeding Test With Silage.
243.-Avocado Propagation.
244.-Avocado Culture.
245.-Silage for Milk Production.
INDEX TO REPORT, BULLETINS, AND PRESS BULLETINS.
'AGE
3
4
6
7
12
14
18
19
25
26
28
'29
30
31
31
32
33
34
35
42
43
-60.
49
50
51
52
53
63
64
65
66
67
68
Hon. Sidney J. Catts,
Governor of Florida,
Tallahassee, Fla.
SIR: I have the honor to transmit herewith the annual report
of the Director of the Florida Experiment Station, for the fiscal
year ending June 30, 1916.
Respectfully,
P. K. YONGE,
Chairman of the Board of Control.
BOARD OF CONTROL
P. K. YONGE, Chairman, Pensacola, Fla.
T. B. KING, Arcadia, Fla.
E. L. WARTMANN, Citra, Fla.
W. D. FINLAYSON, Old Town, Fla.
F. E. JENNINGS, Jacksonville, Fla.
J. G. KELLUM, Secretary, Tallahassee, Fla.
STATION STAFF
P. H. ROLFS, M.S., Director.
J. M. SCOTT, B.S., Animal Industrialist and Vice-Director.
B. F. FLOYD, A.M., Plant Physiologist.
J. R. WATSON, A.M., Entomologist.
H. E. STEVENS, M.S., Plant Pathologist.
C. D. SHERBAKOFF, Ph.D., Associate Plant Pathologist.
S. E. COLLISON, M.S., Chemist.
JOHN BELLING, B.Sc., Assistant Botanist and Editor.
S. S. WALKER, M.S., Associate Chemist.
F. F. HALMA, B.S., Assistant Horticulturist.
H. L. DOZIER, B.S., Laboratory Assistant in Entomology.
JULIUS MATZ, B.S., Laboratory Assistant in Plant Pathology.
*LEWIS KNUDSON, Ph.D., work in Plant Physiology.
H. G. CLAYTON, B.S.A., Laboratory Assistant in Animal Industry.
C. D. MCDOWELL, B.S.A., Laboratory Assistant in Plant Phy-
siology.
T. VANHYNING, Librarian.
K. H. GRAHAM, Auditor and Bookkeeper.
E. G. SHAW, Secretary.
L. T. NIELAND, G.F., Farm Foreman.
*Temporary.
Report for the Fiscal Year
Ending June 30,1916
Hon. P. K. Yonge,
Chairman, Board of Control.
SIR: I have the honor to submit herewith my report on the
work and condition of the Agricultural Experiment Station for
the fiscal year ending June 30, 1916, and I respectfully request
that you transmit the same, in accordance with the law, to the
Governor of the State of Florida.
Respectfully,
P. H. ROLFS,
Director.
INTRODUCTION
The unprecedented development of Agriculture in the State
during the last year has called for an increasingly larger amount
of information that the Experiment Station has been able to
give. The work begun several years ago has been continued
without interruption. Unfortunately it has been impossible,
with the funds at our command, to cover all the lines of work
that the agricultural people of the State are now demanding to
be investigated. The Experiment Station staff has been called
upon at numerous times to furnish exact data regarding various
lines of investigation that have been carried on heretofore.
Fortunately, all agricultural questions of a general nature can
be referred to the Extension Division, thus freeing the Experi-
ment Station staff from importunities excepting along the lines
of its special investigations. The staff has been able to devote
comparatively more time to investigational work of a broad
nature than heretofore.
LINES OF WORK
The lines of work carried out during the last fiscal year have
been essentially the same as those laid down some years ago.
Portions of some of the Projects have been completed and pub-
lications issued on these.
Florida Agricultural Experiment Station
PLANT INTRODUCTION PROJECT.-The Experiment Station has
continued to cooperate with the United States Department of
Agriculture in testing new and apparently valuable domesti-
cated plants. The following twenty-seven grasses have given
more or less promise in the several years test which they have
undergone at the Experiment Station:
Andropogon annulatus Melinis minutiflora
Andropogon barbindos Panicum molle (muticum) ?
Andropogon propinques Para Grass
Anthephora hermaphrodita Paspalum notatum
Chaetochloa aurea Paspalum dilatatum
Chrysopogon montanus Panicum maximum
Capriola dactylon Panicum palmifolium
Cenchrus biflorus Panicum Capim de Angola
Cymbopogon rufus Panicum hirsutissimum
Eleusine coracana Pennisetum Ruppelianum
Erichloa subglabra Pennisetum purpureum
Eragrostis curvula Saccharum ciliare
Eragrostis chloromelas Sudan grass
Eragrostis abyssinica Tricholaena rosea
A number of these are already widely distributed in the
State; others are being tested for forage value tho they are
ordinarily used for ornamental purposes.
Especial attention has been given to the introduction and
propagation of velvet beans. A number of these varieties have
proved to be of special merit and have been distributed to va-
rious farmers in the State. Several varieties of the hybrid
velvet beans, originated at the Experiment Station, have been
continued in the plot grounds. These will be tried for a num-
ber of years more, with the possibility of some varieties proving
superior to those now commonly grown.
DAIRY PROJECT.-The principal work of the Animal Industry
Department has been confined to testing the dairy herd and to
the determination of the feed cost of milk when produced from
Florida-grown forage. Accurate data has been kept as to the
milk flow of each individual animal owned by the Experiment
Station.
Somewhat extended tests' have been carried on in comparing
the value of sorghum silage and Japanese-cane silage for win-
tering stock.
The new dairy barn has added greatly, to the value and ac-
curacy of the work conducted in this line. A novel feature
Annual Report, 1916
in connection with this dairy barn is a concrete silo for the
preservation of sweet-potato silage. The work conducted in this
line shows that it is practicable to preserve sweet potatoes for
cattle feeding and hog feeding purposes.
PLANT PHYSIOLOGY PROJECT.-In the Department of Plant
Physiology the work has been conducted along two principal
lines: (1) Study of the toxic effects of certain organic chem-
icals when applied to certain growing citrus plants; and (2) a
study of the effect of fertilizer combinations and sources upon
the growth of citrus seedlings. The underlying subject with the
Plant Physiologist is that of discovering the cause and securing
a remedy for a very widely prevalent citrus disease known as
dieback. When the problem was first approached it seemed as
if it would be of rather easy solution, but the further the sub-
ject is studied the clearer it becomes that the question is an
extremely complicated one. The analyses of soil taken from the
region occupied by trees affected with this disorder show the
presence of a considerable amount of vanillin; it was therefore
thought that vanillin might have some causative relation to die-
back. The rather careful and extended experiments made in this
direction seem to throw considerable doubt on this hypothesis.
Another line of study that was taken up in the field is con-
cerned with the value of ground limestone when applied to
citrus groves. It had been noted that under certain limited
conditions the effect following upon an application of ground
limestone was deleterious to the grove. From rather extended
field observations it appears quite clear that limestone, under
certain limited conditions, induces injury to citrus trees which
manifests itself in the form of chlorosis. The exact manner in
which the lime produces this disadvantageous condition is still
somewhat in doubt.
ENTOMOLOGY PROJECT.-The principal studies during the
summer and fall of the past fiscal year were directed toward a
full understanding of the life history and distribution of the
velvet-bean caterpillar (Anticarsia gemmatilis). This work has
been brought to a sufficient degree of advancement that it is
thought probable this subject matter will be closed during
the present fiscal year.
A considerable part of the time during the winter, spring
and early summer was devoted to the study of flower thrips,
especially those thrins that cause greater or less injury to cit-
rus, tomatoes and other agricultural crops. In connection with
Florida Agricultural Experiment Station
flower thrips, special attention was given to (1) the seasonal
history and greater abundance in dry weather, and (2) greater
extent of damage to citrus. Incidentally, several other forms
of thrips were studied. It was also found that the flower thrips
does not confine its entire activities to citrus.
Preliminary studies were begun on the use of Cyanamid and
other material for combating root-knot, especially as to its use-
fulness under ordinary agricultural practice.
PLANT PATHOLOGY PROJECT.-This Project concerns itself
with three principal lines of work: (1) Diseases affecting
citrus trees and fruit; (2) diseases affecting truck crops; and
(3) diseases affecting the pecan tree and fruit.
In the citrus-disease work principal attention was given to
the disease known as gummosis, the causative agent of which
is not known. The subject is somewhat difficult to handle as the
disease progresses rather slowly and it has been very difficult
to ascertain the causative agent or agents.
A considerable amount of work has also been done in study-
ing the bacterium causing citrus canker.
From time to time considerable uneasiness has been caused
among citrus growers by the appearance in the grove of what
seemed to be a rapidly developing disease. A number of times
different pathologists of the Experiment Station have been
called upon to give advice in this direction. On several different
occasions the peculiar manifestation has been found to be light-
ning injury.
The principal work in truck diseases has been directed toward
studying the disorder of seed beds usually spoken of as damp-
ing off." Studies on this problem have shown that it is by no
means a simple question. It has also been shown that more
good can be done in the preventive direction than in the direc-
tion of curing a seed bed after it is affected with damping off.
Somewhat extended attention has been given to the tomato
disease popularly known as buckeye rot."
Careful attention has been given to the study of diseases af-
fecting pineapple plants.
A somewhat extended and careful study has been made of the
disease known as pecan dieback. This has been shown to be
due to Botrysphaeria berengeriana. Methods of control have
been introduced in extensive groves. By following up the prun-
ing-out method considerable good can be done to trees severely
affected with this disease. This wound parasite seems to be
10R
Annual Report, 1916
unable to produce infection on uninjured surfaces of the pecan
tree.
A new disease of the fig has been discovered and somewhat
carefully studied. It has been shown to be due to a new species
of fungus described under the name of Rhizoctonia microscle-
rotia.
SOILS AND FERTILIZERS PROJECT.-In this Project the main
attention during the year has been given to the study of fer-
tilizers and to soil conditions as affected by fertilizers that have
been applied to the Experiment Station grove during the last
seven years. A considerable amount of time from the Chemist
and Associate Chemist has also been given to the continuation
of analyses of drainage waters from the lysimeter tanks on the
Experiment Station grounds.
PLANT BREEDING PROJECT.-In the Plant Breeding Project,
entire attention has been given during the last fiscal year to the
further development of velvet-bean hybrids and the fixing of
certain races and varieties. Attention has been given to further
propagation of prominent varieties with a view to utilizing
them as farm crops.
CHANGES IN STATION STAFF.-From July 1, 1915, to July 1,
1916, the following changes took place:
On October 1, Lewis Knudson, Ph.D., Cornell University,
began temporary research work in the Laboratory of Plant
Physiology. On October 31, John Schnabel resigned the po-
sition of Assistant Horticulturist. On October 31, C. D. Mc-
Dowall, B.S., University of Florida, resigned the position of
Laboratory Assistant in Plant Physiologist. On November 1,
F. F. Halma, B.S., University of Florida, began work as Assist-
ant Horticulturist. On December 31, A. C. Mason, M.S., Uni-
versity of Florida, resigned the position of Laboratory As-
sistant in Entomology. On December 31, Dr. Lewis Knudson
completed the work he had been carrying on in the Laboratory
of Plant Physiology. On January 1, H. L. Dozier, B.S., Uni-
versity of South Carolina, began work as Laboratory Assistant
in Entomology. On June 30, John Belling resigned the position
of Assistant Botanist and Editor.
12R Florida Agricultural Experiment Station
'PUBLICATIONS
PRESS BULLETINS
No. Title Date and Author
239 Bulletins and Reports on Hand---- --------..................................-- Nov. 13, 1915
240 Fertilizer Test of Sweet Potatoes....................Feb. 12, 1916-J. M. Scott
241 The Time of Ripening of Velvet
Bean Varieties...................................... March 25, 1916-J. Belling
242 Feeding Test with Silage ...... ..................April 8, 1916--J. M. Scott
243 Avocado Propagation----- -------............. .....................April 23, 1916-P. H. Rolfs
244 Avocado Culture..... .----...... ----- ....-- ..April 29, 1916-P. H. Rolfs
245 Silage for Milk Production...................... May 20, 1916-J. M. Scott
BULLETINS
128 Citrus Canker, III ..........--.......-- ......... ..Nov. 1915-H. E. Stevens
129 Japanese Cane.......------.......................------ Jan. 1916-J. M. Scott
130 Control of the Velvet Bean Caterpillar...........June, 1916-J. R. Watson
131 Pig Feeding---..... .........-------...June,-1916-J. M. Scott
ANNUAL REPORT for 1915; 131 pages, with index
to all publications of the year.
Annual Report, 1916 13R
REPORT OF AUDITOR
P. H. Rolfs, Director.
SIR: I respectfully submit the following report of the credits
received and expenditures vouchered out of the funds as speci-
fied:
RECEIPTS
By balance on hand, July 1, 1915 ..................
By Appropriation from U. S. Treasury........ $
By receipts, Sales Fund................................. ..
State Experiment Fund. ................- .... ..
State Repair and Building Fund-..........
State Printing Fund ............. ......... ... .. ..
Totals .....-........---------------- $
EXPENDITURES
By-
Salaries .. ... -----------..-- .----- $
L abor ... ....... ... .........'... . .. ............ ...
Publications ..-..... .......................
Postage and stationery.............................
Freight and express........................... ..
Heat, light, water, and power .....................
Chemicals and laboratory supplies.............
Seeds, plants, and sundry supplies................
Fertilizers ............... ............ .... ......
Feeding stuffs .............. -- ---...- ...
Library .......... . ...... ......... ......... ......
Tools, machinery and appliances...................
Furniture and fixtures........................-.....
Scientific apparatus and specimens.............
Livestock .......... ......... .......... ....... ... ..
Traveling expenses .-. ............ .- .....
Contingent expenses. .. .......... .......- -
Buildings and land........... .....- .........
Balance ...........
Totals .......
1
;i.
Other
Hatch Adams Sources
.---------- ......... ........ $ 307.46
5,000.00 $15,000.00 ...............
............ .... ... .... 2,977.10
... ..... ...... ...... .... 2,000.00
........-- -.. 2,500.00
.-.. -- -...... ... ....- .. 3,750.00
5,000.00 $15,000.00 $11,534.56
'-' .
8,296.68 $11,772.84
2,541.35 747.21
714.72 -.........
691.13 16.47
176.88 140.13
101.64 112.70
.. ........... 651.73
156.16 323.08
-..-......... 55.51
1,245.22 .................
478.61 19.82
125.80 137.02
84.63 99.66
.......... .... 87.17
........... .............
24.60 777.98
342.58 .................
342.58 58.58,
$
266.67
826.69
43.13
20.87
55.34
100.84
92.93
806.45
23.99
186.48
752.50
31.03
3.80
57.77
16.07
............................ $15,000.00 $15,000.00 $ 3,284.56
Respectfully submitted,
K. H. GRAHAM,
Auditor.
Florida Agricultural Experiment Station
REPORT OF ANIMAL INDUSTRIALIST
P. H. Rolfs, Director.
SIR: I submit the following report of the Department of
Animal Industry for the year ending June 30, 1916.
DAIRY HERD
During the year six grade and one purebred Jersey cows were
added to the herd. The purebred Jersey cow was Creole's
Lassie Sue No. 306835 by Fern's Blue Fox No. 83359, he by
Sport of Oakhurst No. 72207, out of Belmont's Creole Girl No.
199448, out of Belmont Beulah No. 163856 by Tease's Golden
Lad No. 57781.
No other animals were added to the herd except from the
increase in calves. Only the most desirable heifer calves were
retained. The grade bull calves were all sold for veal and two
undesirable heifer calves were also disposed of. Two purebred
Jersey bulls were sold within the year.
Elbertas' Eminent Fox No. 135708 was sold to the Florence
Villa Fruit Co., Florence Villa, Florida, and Queen's Joyous
Lad No. 134230 was sold to Ben T. Arnow, Gainesville, Florida.
The following table shows which cows dropped calves during
the year, by which bull, and what disposition was made of the
calf:
FIG. 1.-Magnolia's Noble Pogis 131234.
14R
16R
Florida Agricultural Experiment Station
FIG. 2.-Prince Lanseer Tormentor 130913.
The entire herd numbers 33 cows, 12 heifers, 9 calves and 3
bulls; a total of 57 head. Of this number 18 head are purebred
Jerseys.
Table 2 gives age and breed of cows and time in milk.
TABLE 2
AGE AND BREED OF COWS, AND TIME IN MILK
0 I
1 8 Grade Jersey
9 8 Grade Jersey
15 7 Grade Jersey
17 5 Jersey
18 5 Jersey
20 5 Jersey
21 4 Grade Jersey
22 4 Grade Jersey
24 4 Grade Jersey
25 4 Grade Jersey
26 4 Grade Jersey
41 4 Grade Jersey
59 3 Jersey
60 12 Grade Jersey
61 7 Grade Jersey
62 3 Grade Jersey
63 7 Grade Jersey
65 7 Grade Jersey
69 3 Grade Jersey
7
S 0
Sept. 21, 1914 366
Nov. 21, 1915 328
Nov. 13, 1915 160
Sept. 4, 1915 297
Feb. 23, 1916 251
May 31, 1915 366
Nov. 15, 1915 225
Oct. 4, 1915 126
Dec. 5, 1915 206
Dec. 3, 1915 318
Oct. 19, 1915 302
Dec. 19, 1915 277
Apr. 9, 1915 350
... 329
160
S277
.............. 248
210
Jan. 2, 1916 181
Apr. 30, 1916
Apr. 22, 1916
Nov. 2, 1915
Feb. 9, 1916
Sept. 22, 1915
Dec. 24, 1915
Dec. 17, 1915
Apr. 21, 1916
Apr. 19, 1916
Annual Report, 1916 17R
Table 3 shows the amount of milk and butter per cow from
July 1, 1915, to June 30, 1916.
TABLE 3
RECORD JULY 1, 1915, TO JUNE 30, 1916
Table showing cow number, pounds of milk, percent of butter fat, pounds
of butter, value of butter at 40 cents per pound, gallons of milk, value of
milk at 32 cents per gallon, cost of feed, and profit over cost of feed.
0) 0)
2907.7 6.0 360.75 168.35 686.9 219.81 94.86 124.95
.0 4.5 66.28 30.93 168.5 53.92 3.57 20.55
17 2404.0 5.1 123.40 57.59 279.5 89.44 54.76 34.68
18 3248.9 5.5 179.43 83.76 377.7 120.86 42.85 78.01
20 4613.7 4.8 224.30 104.67 536.5 171.68 101.52 70.16
21 4009.6 4.6 185.45 86.54 466.2 149.18 50.85 95.33
22 1181.4 4.3 51.40 23.99 137.4 43.97 22.07 21.90
24 2540.1 5.7 145.54 67.92 295.4 94.53 43.89 50.64
25 3178.1 5.8 186.81 87.18 369.5 118.24 46.53 71.71
26 3205.3 5.6 182.49 85.16 372.7 119.26 57.94 61.32
41 3626.3 5.4 196.27 91.59 421.7 134.94 49.07 85.87
59 4840.5 5.5 267.53 124.85 562.8 180.09 78.46 101.63
60 4537.9 4.8 219.86 102.60 527.6 168.83 78.87 89.96
61 1813.6 5.5 100.68 46.98 210.9 67.49 30.42 37.07
62 3004.2 5.5 167.77 78.29 349.3 111.78 47.37 64.41
63 2960.1 4.3 129.82 60.58 344.2 110.14 66.34 43.80
65 2174.6 4.9 107.38 50.11 252.8 80.89 40.36 40.53
69 3746.2 4.0 150.15 70.07 435.6 139.39 35.86 103.53
FIG. 3.-Purebred and grade Jersey heifers raised on the Experiment Sta-
tion farm.
Florida Agricultural Experiment Station
EXPERIMENTS CONDUCTED WITH HERD
Two experiments in milk production were conducted during
the year.
SORGHUM SILAGE AND JAPANESE-CANE SILAGE COMPARED
The first was a comparison of sorghum silage and Japanese
cane silage for milk production. .The experiment began Jan
uary 18 and ten cows were used in the test. These ten cow
were divided into two lots of five each. The experiment wa
divided into four periods of 16 days each, with four days be
tween each period for changing feeds.
TABLE 4
DAILY RATIONS PER COW.
Lot I. Lot II.
Feeds Used Pounds Feeds Used Pound,
Wheat Bran........................ 7.6 Wheat Bran.................... 7.6
Cottonseed Meal................ 3.8 Cottonseed Meal............. 3.8
Sorghum Silage.................. 15.0 Japanese-cane Silage........ 15.0
During the first period each lot of cows were fed the fore
going ration. During the second period the feeds were re
versed; that is, lot I received the rations given lot II during
the first period and lot II were given the rations fed lot I during
the first period. During the third period each lot of cows
received the same ration as in the first period. During th<
fourth period each lot of cows received the same ration as ir
the second period.
The sorghum-silage ration produced 539.72 gallons of milk al
a total feed cost of 12.1 cents a gallon. The Japanese-canm
silage ration produced 509.74 gallons of milk at a total feed cos,
of 12.8 cents a gallon. This makes a difference of feed cost pel
gallon of 0.7 of a cent in favor of sorghum silage.
A record of the weight of each animal was taken at the be
ginning of the experiment and at the close of each period. Th<
weights of the cows varied but little during the experiment. Al
cows made a slight gain over the average weight at the begin.
ning. This would indicate that there was no difference between
these two rations in maintaining the animal's initial weight.
The following gives the results in detail:
18R
Annual Report, 1916
TABLE 5
FEEDS CONSUMED AND MILK PRODUCED
First Period, January 18 to February 2, 1916.
19R
Lot I Lot II
Feeds Used Pounds Feeds Used Pounds
Cottonseed meal........-..... ........ 304.0 Cottonseed meal....................... 304.0
Bran ..... ............. ----.. .. 608.0 Bran ..................-...... ............. 608.0
Sorghum Silage.........-........... 1200.0 Japanese-cane Silage........... 1200.0
Milk produced -................-........ 1202.2 Milk produced......................... 1077.6
Second period, February 6 to February 21, 1916
Cottonseed meal................. 304.0 Cottonseed meal................... 304.0
Bran .................... ......- 608.0 Bran ....................................... 608.0
Japanese-cane Silage...-.... 1200.0 Sorghum silage ---.................. 1200.0
Milk produced ............... 1152.2 Milk produced......................- 1159.1
Third period, February 25 to March 11, 1916.
Cottonseed meal........................ 304.0 Cottonseed meal.---.................. 304.0
Bran ...................................... 608.0 Bran ........................................ 608.0
Sorghum silage.................... 1200.0 Japanese-cane silage................ 1200.0
Milk produced.....----......- .. 1201.0 Milk produced .......................... 1100.8
Fourth period, March 15 to March 30, 1916.
Cottonseed meal....................... 304.0 Cottonseed meal......... ..... ...... 304.0
Bran ...............................-- .. 608.0 Bran ............. ...........-....... 608.0
Japanese-cane silage................ 1200.0 Sorghum silage.................... 1200.0
Milk produced........................... 1053.2 Milk produced...-............-:....... 1079.3
FEED COST PER GALLON OF MILK
Cows fed sorghum silage.
1216 pounds cottonseed meal @ $30 a ton ................. .....-.........$18.24
2432 pounds wheat bran @ $31 a ton ............-- ..- ......... $37.70
4800 pounds sorghum silage @ $ 4 a ton........... .....................$- 9.60
Total cost of feed.............-... .....-.... ................$ 65.54
Milk produced-539.72 gallons @ $ .32.................-..... ... ....$172.71
Cost per gallon -----......................------- ------ .1214
Cows fed Japanese-cane silage.
1216 pounds cottonseed meal @ $30 a ton .............-- ~..-.. ~... $18.24
2432 pounds wheat bran @ $31 a ton...................-- ..-..$37.70
4800pounds Japanese-cane silage @ $ 4. a ton......... ...-.............. $ 9.60
Total cost of feed........ .-- .......----- -..................... $ 65.54
Milk produced-509.74 gallons @ $ .32.....--.---........................ $163.10
Cost per gallon...-................---- ......... ...........$ .1285
Florida Agricultural Experiment Station
TABLE 6
WEIGHTS OF COWS
January 19, 1916, Beginning of first period.
Lot I Pounds Lot II Pounds
Cow No. 60 .... .. ...... .... 750.0 Cow No. 26 .... ....... .. 648.0
Cow No. 25 ...............-.. 508.0 Cow No. 20 ~............... 795.0
Cow No. 9.. ... ........... --.. 893.0 Cow No. 21........................... 763.(
Cow No. 24 .... ............... 622.0 Cow No. 59...... .................... 576.0
Cow No. 41 ..--..........-.. .. 611.0 Cow No. 1 -.........--....- ......... 938.0
Average .................. 676.8 Average .....................744.0
February 2, 1916, End of first period.
Cow No. 60 .................... 726.6 Cow No. 26....................... 641.C
Cow No. 25..............-..-. 495.0 Cow No. 20 ....... ............ 779.0
Cow No. 9......................- 886.6 Cow No. 21..........................- 753.3
Cow No. 24... .............. 618.6 Cow No. 59............ .............- 553.3
Cow No. 41..-......---... ...-.... 625.6 Cow No. 1............................ 898.0
Average .....-..... --.....-- 670.5 Average ......................... 725.
February 22, 1916, End of second period.
Cow No. 60.......-............... 733.3 Cow No. 26...........- ....-..... 650.0
Cow No. 25....................... 517.3 Cow No. 20............ .............- 805.0
Cow No. 9..................... 888.3 Cow No. 21... ................... 756.6
Cow No. 24...................-- ...-- 629.6 Cow No. 59........................... 576.6
Cow No. 41 .......... ............. 635.0 Cow No. 1...................... .... 918.3
Average .......-.............. 680.7 Average ..................... 741.3
March 11, 1916, End of third period.
Cow No. 60..................734.0 Cow No. 26.......... .............. 662.3
Cow No. 25..... ..............- 521.6 Cow No. 20........................... 803.3
Cow No. 9 .....-..-.............-. 896.6 Cow No. 21.............. .... 769.0
Cow No. 24...................... 633.3 Cow No. 59................. .... 567.3
Cow No. 41................... .... 643.3 Cow No. 1........................ ... 930.0
Average .................... 685.8 Average ....................... 746.4
March 30, 1916, End of fourth period.
Cow No. 60..--................ 740.6 Cow No. 26.......... ......... 678.3
Cow No. 25............-......--.. 528.3 Cow No. 20....--................... 816.6
Cow No. 9..-................ 918.3 Cow No. 21....................... 763.3
Cow No. 24............ 630.0 Cow No. 59........................ 596.6
Cow No. l................ ..... 680.0 Cow. No. 1.....------............ 925.0
Average ..................... 699.4 Average ...... ......... 756.0
SORGHUM SILAGE AND SWEET-POTATO SILAGE COMPARED
The second experiment was a comparison of sorghum silage
and sweet-potato silage for milk production.
Ten cows were selected from the dairy herd and divided into
two lots. The two lots of cows were as nearly equal in all
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Annual Report, 1916
respects as it was possible to get them. The test began May 9
and continued for 43 days, closing June 20. The test was di-
vided into two periods of 20 days with three days between pe-
riods for the purpose of changing feeds.
The following table gives the daily ration fed each cow in
each lot.
TABLE 7
DAILY RATION PER COW
Lot I Lot II
Feeds Used Pounds Feeds Used Pounds
Wheat Bran ............... 8.42 Wheat Bran ......... .---... 8.42
Cottonseed meal............ 2.80 Cottonseed meal.............. 2.80
Sweet-potato silage........ 10.60 Sorghum silage................ 15.20
During the first period each lot of cows were fed the fore-
going ration. During the second period the feeds were re-
versed; that is, lot I received the rations given lot II during the
first period and lot II received the rations given lot I during
the first period.
The'sorghum-silage ration produced 280.9 gallons of milk at
a total feed cost of 14.8 cents per gallon.
The sweet-potato silage ration produced 307.1 gallons of milk
at a total feed cost of 15.4 cents per gallon. This shows a dif-
ference of 0.6 of a cent per gallon in favor of sorghum silage.
TABLE 8
FEEDS CONSUMED AND MILK PRODUCED
First period, May 9 to May 29, 1916.
Lot I Lot II
Feeds used Pounds Feeds used Pounds
W heat bran........ ................. 842.0 W heat bran.................-.... ... 842.0
Cottonseed meal.................. 280.0 Cottonseed meal.................. 280.0
Sweet potato silage............. 1060.0 Sorghum silage .-........ ....... 1520.0
Milk Produced.........-............ 1310.9 Milk produced................... 1202.2
Second period, June 1 to June 20, 1916.
Wheat bran-....................- 842.0 Wheat bran......-..................- 842.0
Cottonseed meal....... ...... 280.0 Cottonseed meal.................... 280.0
Sorghum silage ..................... 1520.0 Sweet-potato silage---.........- 1060.0
Milk produced.................... 1213.7 Milk produced.............-......-- 1330.1
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Florida Agricultural Experiment Station
FEED COST PER GALLON OF MILK
Cows fed sweet potato silage.
Wheat bran............................ 1684 pounds @ $31.00 a ton............ $26.10
Cottonseed meal ........................ 560 pounds @ $30.00 a ton............ $ 8.40
Sweet potato silage....-.......... 2120 pounds @ $13.00 a ton.............. $13.98
Total cost of feed.............................. ...................- -... .... $48.48
Total milk produced, pounds........... ........................ ..... ...... 26.41
or, gallons ..................... ......................................307.1
Feed cost per gallon -... ..... ........ ...... ......... ...$ .158
Cows fed sorghum silage.
Wheat bran............... .... 1684 pounds @ $31.00 a ton................ $26.10
Cottonseed meal .--.................. 560 pounds @ $30.00 a ton........... $ 8.40
Sorghum silage-......................- 3040 pounds @ $ 3.00 a ton...............- $ 6.08
Total cost of feed......-...........-... -.......--.......$40.58
Total milk produced, pounds......................... -.. ............. 2415.9
or, gallons ......................... .............. ...... .. ......... 280.9
Cost per gallon................................................ ........... $ .144
TABLE 9
WEIGHT OF COWS
May 9, 1916, Beginning of first period.
Lot I Pounds Lot II Pounds
Cow No. 21..........--.........-.... 787.3 Cow No. 41..................... 667.3
Cow No. 18........................-- 697.3 Cow No. 69......-.................... 715.0
Cow No. 26..................... 715.0 Cow No. 25..................... 543.0
Cow No. 31........-.......- 525.0 Cow No. 24..........................t. 660.0
Cow No. 62......- ......... .. 570.0 Cow No. 20....................... 870.0
May 28, 1916, End of first period.
Fed sweet-potato silage Fed sorghum silage.
Cow No. 21- ...............- .... 781.6 Cow No. 41............................ 661.6
Cow No. 18 ..-........ ..........-- 706.6 Cow No. 69.... .....................-- 729.0
Cow No. 26........................ 733.3 Cow No. 25 ........................... 555.0
Cow No. 31-........-.....-............ 553.3 Cow No. 24.... ..-................. 678.0
Cow No. 62.....-...........-.......... 601.6 Cow No. 20..................... ...-- 886.6
June 20, 1916, End of second period.
Fed sorghum silage. Fed sweet-potato silage.
Cow No. 21 -.. ....- .............. 882.3 Cow No. 41............................ 684.6
Cow No. 18 ..................-......- 710.6 Cow No. 69............................ 722.3
Cow No. 26..---...............-- ...- 748.0 Cow No. 25...........................- 583.3
Cow No. 31.. -....-.............-- ... 588.0 Cow No. 24 --........................ 674.6
Cow No. 62 -.................-.....- 613.3 Cow No. 20 ........................... 902.3
TEST FOR TUBERCULOSIS
On May 27, 1916, the entire dairy herd was tested for tuber-
culosis by Dr. W. A. Munsell of the State Board of Health. Not
an animal in the herd reacted. The herd has been tested several
times within the last ten years. So far, we have never had a
case of tuberculosis on the Station farm.
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Annual Report, 1916
COMPARISON OF SORGHUM SILAGE AND JAPANESE-CANE SILAGE
FOR WINTERING CATTLE
An experiment was begun. December 8, 1915, and continued
for sixty days, to compare the value of sorghum silage and Jap-
anese-cane silage for feeding young cattle during the winter.
The experiment was not planned with any idea df fattening
the animals. The main object was to see if the animals would
maintain their initial weight during the winter when fed on
silage and a small allowance of cottonseed meal.
The animals used in this test were grade Jersey heifers from
fifteen to thirty months old." They were divided into two lots,
as nearly equal in weight and quality as possible. Those in lot
I were fed all the sorghum silage they would eat, about thirty
pounds each, and one pound of cottonseed meal each, daily.
Those in lot II were fed an equal amount of Japanese-cane
silage and one pound of cottonseed meal daily.
The animals fed sorghum silage and cottonseed meal for sixty
days gained an average of 8.25 pounds each. Those fed on
Japanese-cane silage and cottonseed meal just maintained their
weight.
HOGS.
Since the last report, the Berkshire boar, Handsome Lee's
Baron 3d No. 215322 was bought. Handsome Lee's Baron 3d
No. 215322 was sired by Handsome Lee's Rival No. 133488 and
out of Maramech's Matchless Lady 3d No. 184977. This boar
has already proven himself a good breeder.
JAPANESE-CANE FERTILIZER EXPERIMENT
Two crops have been harvested from the Japanese-cane fer-
tilizer experiment. The results obtained up to this time are not
sufficient to warrant drawing any definite conclusions. There is
one very noticeable fact brought out when the yields per acre
obtained in 1915 are compared with the yields obtained in 1914.
There is a very noticeable decrease. The decrease in some plots
is more than 50 percent. On some of the plots the decrease
in yield was not more than 10 to 20 percent. These results are
very similar to data obtained in a previous fertilizer experiment
with Japanese cane (see Fla. Agr. Exp. Sta. Bul. 129). That
is, there was a gradual decrease in yield after the first year.
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Florida Agricultural Experiment Station
TABLE 10
JAPANESE-CANE FERTILIZER EXPERIMENT
0
E
--........
3 ........
4........
5........
6 ........
7 --------
8 ........
9* ------
10 ........
5-......
11........
9*.
10........
11........
12........
13........
14........
15........
16.......
17........
18-.....
19........
20*......
21........
22........
23
Fertilizer applied, pounds per acre
o o i
P84 4 i I W
84- 150 .... ....... 60
84 ..... .. 2 . 5 ....... ..... .g 1 5 Z..... 60
84 ............ ............ ..3o. ....... 1 ........ ........ 60.
---- 123.5----- -------- 150 ...--- 60
--. .. ---- ..-- ----------- ~ I ----- -- -- 3 -- ---- I I- ........ --------
.... 123.5 ....-- .... --..... ........ ....... 60
84 .-------------...... ---.......... ------ 150 ..... -- 60
84 ............-------- ..........--.... ....--.. 75 60
84 ........ .. ..-. .... ... ....... ...... 60
84 - ----- ----- --- ---- ---- 133 60
--------- ---------- --------------- --------
84 --------........--........ -- -------- ........ 133 60
84 '- ----- ---------- ........ -- 75 ........ ........
.... 123.5 .--........-...- .... ..... 75 ... ........
..-... ....-.- .. 116.6 .... .. ........-- ........ 60
....... 123.5 ............ .....- ..... ........ -...-.----.. 60
84 -----------.. .. ........ -- ... ..... 60
--...... ..... 133 ..
..... ........... ......... .. ..... .... .... --.. 60
............ ... .. ..... ......... ........
........ ........ ............ ........ 150 ... 1--- -
...-------- ------- --- -- ---........ ... ..
.............. 123 ............ ........ ..... ........
........ ............ 116.6 ........... 1..... .....- .. .......
84 i ............ ............ ........ ........ ........ ........ ........
Yield per
acre, tons
green
o material
r. 4 1914 1915
30
ow
2000 17.03 13.3
2000 14.42 12.95
S32.67 13.65
........ 32.67 13.65
.... 12.31 11.20
........ .15.97 11.20
...... 17.11 12.16
2000 16.85 11.90
........ 16.68 9.36
9.63 7.17
2000 12.77 7.17
........ 14.38 8.31
..1... 13.41 7.00
....... 14.11 7.35
-.. 9.02 8.22
........ 12.10 8.75
9.14 7.70
....... 9.09 7.08
6.79 5.42
8.40 5.68
.-...-. 6.67 3.93
... 7.05 6.56
........ 14.03 7.78
........ 9.45 7.70
*Check plots. fLoads.
COWPEAS, YIELD OF FORAGE AND GRAIN
Four varieties of cowpeas were tested last year for yield of
forage and also yield of seed. The varieties used were Monetta
S. P. I. No. 1541, Brabham, S. P. I. No. 27863, and S. P. I. No.
27864.
TABLE 11
COWPEAS; YIELD OF FORAGE AND GRAIN
Variety
Monette S. P. I. No. 1541...............
Brabham -.............................-- ... ..
S. P. I. No. 27863......--.....-----................
.S. P. I. No. 27864...........- -.......... .......
Yield of Forage, Yield of Seed in Pods,
Pounds per acre. Pounds per acre.
... 1705.1 531.7
...- 1577.9 517.3
-... 327.0 258.2
S301.3 -.
The restilts of this year's work indicate that Monette S. P. I.
No. 1541 has given best results. However, there is but little
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_I _
Annual Report, 1916
difference in the yield of seed in pod between the Monette and
Brabham.
CHINESE VELVET-BEAN FERTILIZER TEST
One acre of Chinese velvet beans were used for a fertilizer
test. The acre was divided into six plots of equal size. One
row was left between each plot so that the fertilizer on one plot
would have no effect on the adjoining plot. The beans were all
planted at the same time, April 12, 1915, and the fertilizer was
applied April 30, 1915.
TABLE 12
CHINESE VELVET-BEAN FERTILIZER EXPERIMENT
Yield per acre
Plot Fertilizer applied Pounds Beans in Pod,
Number Per acre Pounds
1................................Ground Limestone ......-...............- 2,000 596.4
2 ...............................Check ................... .......... ....... 616.0
3 ...............................Thomas slag ......................... ... 360 658.4
4 ............... .......Acid phosphate ........-........... ........ 400 583.9
5................................Check ........ .... ..... ....... ........ 642.8
6............................ Raw phosphate ................ ......... 200 601.8
These results indicate clearly that an application of ground
limestone or fertilizer has no effect on increasing the yield of
Chinese velvet bean seed, there being a difference in yield of
only 84.4 pounds per acre between the highest and lowest yields.
The highest yield, 658.4 pounds, was obtained from plot 3, to
which Thomas slag was applied. Plot 5, to which no fertilizer
was applied, produced a yield of 642.8 pounds, a difference of
only 15.6 pounds per acre in favor of the Thomas slag. This
small difference is easily within the limit of error.
VELVET BEANS, YIELD PER ACRE
Several acres of velvet beans were grown last year to deter-
mine the yield per acre of beans in the pod. The results show
quite a variation in yield for the different varieties.
Each of these varieties were grown on acre plots and the
entire acre was harvested and weighed. This really gives actual
field results. A much larger yield can be obtained when grown
on small areas and the yield then reckoned per acre.
YIELD OF VELVET BEANS
Yield per acre
Variety in Pods, Pounds
Chinese .... -...........-- ..... .--.............. 1229.5
Florida ...... ----...... -- .. .................... 1320.0
Wakulla ............... ......------.........-- ...856.0
Osceola -- .. -- ... .....-...... ..... .. ..... ........ 1394.6
Yokohama ............... .............. .. ........ 1893.0
25R
Florida Agricultural Experiment Station
COTTON, YIELD PER ACRE
Four acres of cotton were grown last year. The four acres
produced a total yield of 1,398 pounds of seed cotton, or an
average yield per acre of 349.5 pounds. The yield on these four
acres varied greatly. The highest acre yield was 497 pounds
and the lowest was 210 pounds of seed cotton.
The following amounts of fertilizer were applied, per acre:
Sulphate of Ammonia ....... .... ......... .......................... 50 pounds
Sulphate of Potash -......- .----...... .......................... 50 pounds
Acid Phosphate -...... ...................- ........ ........ .......... 175 pounds
Total........... ........................................... .............................275 pounds
The work of selection is being continued.
SORGHUM YIELD
The following figures show the yield of sorghum produced on
the Station farm, as green forage, dry forage, and the yield of
seed in the heads:
Green Weight Dry Weight
Variety Pounds per Acre Pounds per Acre
Sumac, Seed Heads ...................--............... ..... 1236.25 1129
Sumac, Forage -..........------...... .. ----......... . .. 9512.00* *3037
*Average of two acres.
REPLANTING JAPANESE CANE
Heretofore the general opinion has been that Japanese cane
will continue to produce good yields of forage for an indefinite
period. From the results of experiments conducted during the
last eight years we have found that the yield of green material
decreased each year after the first year. We have no theory as
to why there is a decrease in yield each year. If the decrease
in yield was due to soil exhaustion this could be shown by re-
planting the cane. Replanting the cane should show no increase
in yield if the decrease in yield was due to soil exhaustion.
A plot of ground was selected in the spring of 1915 that had
grown Japanese cane continuously since 1908. This plot had
been used for Japanese-cane fertilizer experiments from 1909
to 1914 inclusive, hence we had a complete record of the fer-
tilizer applied and yield obtained each year.
The following table shows the amount of fertilizer applied
per acre and the yield in tons of green material per acre each
year since 1909 to 1914 inclusive:
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Annual Report, 1916 27R
TABLE 13
JAPANESE-CANE FERTILIZER TEST, 1909 TO 1914
Fertilizers, pounds per acre
Plot Plot Plot Plot Plot Plot Plot Plot
Fertilizer I II III IV V VI I VIII
tDried blood ........... -- 112 112 1-12 -.._- 112 112
$Sulph. of ammonia ....... ..--......72 ...... 72 .......... .
Muriate of potash... 84 84 84 .......... .......... ..........
Sulphate of potash .. ........... ..... .....-. -........ -......- ... 84 84 84
Acid phosphate ............. 224 224 224 224 224 224 224
*Ground limestone.. ........ ......... ---- - ... .. .. ...... --2000
Yield, in tons of green material per acre
1909 --.................... 24.20 17.70 16.10 19.10 19.54 18.90 16.60 27.03
1910 ......................... 14.60 12.40, 10.00 14.40 11.80 16.70 14.10 16.00
1911 .....................-- .... 7.08 9.00 9.63 14.36 13.56 15.48 14.02 14.10
1912 .......................... 6.38 6.84 3.68 7.92 7.26 9.62 10.68 10.28
1913 ..........-............... 8.16 6.93 3.83 8.51 8.09 7.86 9.33 8.92
1914 ---.---------- 5.31 '5.05 2.071 6.87 5.25 6.73 7.26 5.89
Average for 6 years 10.951 9.65 7.55 11.87 10.91 12.54 11.99 13.70
*Ground limestone was applied in 1909, 1911, and 1913.
tThe dried blood contained 16 percent of ammonia.
tThe sulphate of ammonia contained 25 percent of ammonia.
After growing Japanese cane on this plot for six years it
was plowed up. On March 6, 1915, a part of each of the eight
plots was replanted with Japanese cane. The new cane was
planted in the same rows that had grown cane for six years.
Each plot of the replanted Japanese cane was fertilized in the
same way as the plots had been for the previous six years. (See
foregoing table.)
The following yields per acre of green material were obtained
from each plot in the fall of 1915:
Tons
Plot I .... ...- ..-- ....- ..- ... .. . .-- ...... ........... ..... ... .. 29.5
Plot II ----........ ..........--- ---..... ....... .......... .... 31.9
Plot III .. ............. -- ----.-.....-...-- --....--....... .18.0
Plot IV ..-......--.-.....-...-..---------------..- ..---.--.--....... 24.2
Plot V ......... ........... ... ...... .......... 29.7
Plot VI ...-.. -..........-.........-.....--..--.. .....--...... 24.9
Plot VII .-..-...-.............----.-.- .. -..............-..-...-....-. 27.3
Plot VIII* ...-.....-- ..... .. ....... ...-- ..---- ........-- --- -...--.....-- ........ ...-- .............. 22.5
*Ground limestone was applied in 1915 at the rate of 2000 pounds per acre.
The replanted cane produced a better yield than the field had
produced before. One would have thought after growing Jap-
anese cane for seven years that the soil would have been almost
exhausted. This, however, did not appear to be so. The ratoon
cane does not produce as heavy a yield of green material per
acre as does the planted cane. These results indicate strongly
the advisability of replanting Japanese cane every three or four
Florida Agricultural Experiment Station
years. All of the plots, except Plot III, gave satisfactory yields.
There is but little difference in the yields produced by Plots
I, II, and V. Plot II, which had received no ammonia for seven
years, gave the heaviest yield of green material per acre. Plot
III, which had received no potash during the past seven years,
gave a yield of only 18 tons of green material per acre. This
is a marked decrease in yield as compared with that of any
of the other plots. This shows the need of potash in a fertilizer
to produce the best yields of Japanese cane.
The yields of Plots IV and VI are nearly equal. Plot VII
produced a yield of 27.3 tons, which is 4.8 tons more green ma-
terial than the yield of Plot VIII. This tends to show that no
benefit was obtained from the applications of ground limestone,
except from the first application in 1909.
SWEET-POTATO FERTILIZER TEST
The land on which this test was conducted had grown Jap-
anese cane for seven consecutive years. The eight plots of.
Japanese cane for six years had had the same amounts and
kinds of fertilizer applied to each plot each year as were applied
to the plots of sweet potatoes in the experiment. After the plots
had grown Japanese cane for seven years it is likely that the
soil of these plots in which any one fertilizer element was omit-
ted was more or less exhausted for that particular element.
Therefore, these results should be considered of some import-
ance as a source of additional information in regard to fertil-
izing sweet potatoes.
The land on which the experiment was conducted was what
would be called a fair grade of high pineland.
FERTILIZERS USED
The same number of pounds of fertilizer was not applied to
every plot, but each plot received the same number of pounds of
plant food of each element. The following amounts of fertilizer
were applied per acre: Plot I; dried blood, 112 pounds, and
muriate of potash, 84 pounds. Plot II; acid phosphate, 224
pounds, and muriate of potash, 84 pounds. Plot III; dried blood,
112, and acid phosphate, 224 pounds. Plot IV; sulphate of am-
monia, 72, acid phosphate, 224, and muriate of potash, 84
pounds. Plot V; dried blood, 112, acid phosphate, 224, and mu-
riate of potash, 84 pounds. Plot VI; sulphate of ammonia, 72,
acid phosphate, 224, and sulphate of potash, 84 pounds. Plot
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Annual Report, 1916
VII; dried blood, 112, acid phosphate, 224, and sulphate of pot-
ash, 84 pounds. Plot VIII; dried blood, 112, acid phosphate,
224, sulphate of potash, 84, and ground limestone, 2,000 pounds.
The first three plots received incomplete fertilizers, the next
four plots were given a complete fertilizer, and the eighth plot
had a complete fertilizer together with ground limestone. The
fertilizer was divided and given in two equal applications. The
first application was made on May 4, and the second on August
19. Triumph sweet potato draws were planted on May 10, in
rows six feet apart, and were set sixteen inches apart in the
row.
RESULTS
The yields per acre were obtained by weighing the sweet po-
tatoes from each plot and figuring them at 60 pounds per
bushel. The yields are given in bushels per acre.
Plot I, 245.6; plot II, 221.6; plot III, 99.6; plot IV; 259.6;
plot V, 252.0; plot VI, 216.0; plot VII, 222; and plot VIII, 269.6
bushels.
It will be seen from these figures that the best yield was
obtained from plot VIII, which was fertilized with dried blood,
acid phosphate, and sulphate of potash, and in addition ground
limestone. However, the yield from plot IV, which was fertil-
ized with sulphate of ammonia, acid phosphate, and muriate of
potash, was nearly equal to that of plot VIII.
The yields obtained from plot I, omitting phosphate, and plot
II, omitting ammonia, are rather surprising, being about equal
to those obtained from any of the four complete fertilizers.
Plot III gave less than one half the yield produced by any of
the other plots in the experiment. This indicates strongly the
need of potash in the fertilizer to produce a satisfactory yield
of sweet potatoes. Even plot II that received no ammonia, gave
more than twice the yield of plot III.
Respectfully,
JOHN M. SCOTT,
Animal Industrialist.
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Florida Agricultural Experiment Station
REPORT OF PLANT PHYSIOLOGIST
P. H. Rolfs, Director.
SIR: I submit the following report of the Plant Physiologist
for the fiscal year ending June 30, 1916.
The two particular lines of work to which attention has been
given during this fiscal year are: (1) The study of the toxic
effects of certain organic chemicals; and (2) a study of the
effect of fertilizer combinations and sources upon the growth
of citrus seedlings. The latter is a continuation of work that
has been under way since 1913.
TOXIC EFFECT OF ORGANIC CHEMICALS ON CITRUS
The study of the toxic effect of certain organic chemicals on
citrus is a phase of the work in connection with the study of
the citrus disease, Dieback. Since this disease is brought on
either directly or indirectly by organic nitrogenous fertilizers
(Fla. Agr. Exp. Sta. Rep., 1912, p. cii) the working theory has
been adopted that the disease is induced directly by the toxic
effect of certain decomposition products arising from the decay
of these organic materials under certain limited conditions. In
adopting this theory, the possibility is recognized that the
disease may be due to the attack of some parasitic organism and
that the method of feeding the plant merely develops suscepti-
bility. But the study of the disease thus far has not supported
this possibility.
The disease, Dieback, manifests itself by the presence of gum
in different tissues of the plant. In the absence of the gum
symptoms, the disease can not be recognized. It is presumed
that the cause of the disease is one that induces gum formation,
and that it is this production of gum with its various accom-
panying secondary physiological disturbances that constitutes
the disease, Dieback.
From a study of the literature of gum formation in other
plants, it is probably safe to conclude that all gum formation is,
in its last analysis, the result of processes in living cells induced
by chemicals from without. The chemicals may be enzymes
or other compounds from fungi, bacteria or other organisms
growing within or attacking the tissues; or they may be chem-
icals originating within the plant from autolytic processes; or
chemicals introduced into or absorbed by the plant.
Since apparently no organisms are associated with the dis-
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Annual Report, 1916
ease that can be considered the causal factor, and since the dis-
ease is brought on by feeding the plants with organic nitro-
genous manures in excess, it is to be concluded that the gum
formation, by which the disease manifests itself, is induced by
chemicals contained in or arising from these manures.
Therefore, the purpose of these experiments is to determine
(1) whether any of the organic compounds contained in organic
nitrogenous manures or arising from them as a decomposition
product can induce gum formation; and if so, (2) whether the
types of gum formation produced are the same as those of
Dieback.
There is a large number of chemical compounds present in or
arising from the decomposition of organic matter in the soil.
Doubtless the character of these compounds varies with the
conditions under which the decomposition takes place. The
selection of a compound for study was determined by the work
of Shorey (Shorey-Journ. Agr. Research 1:357-363). He iso-
lated three organic compounds from soils collected about Die-
back trees. These were benzoic acid, metaoxytoluic acid and
vanillin. The latter was found in such quantities that it could
be isolated from the soil in pure form, a result which had not
been accomplished before. This chemical was selected for the
studies reported herein.
THE ACTION OF VANILLIN ON CITRUS SEEDLINGS
This experiment is one-of a series to determine whether gum
formation will result from the toxic action of vanillin upon
citrus seedlings. It is entirely qualitative.
In Dieback, apparently two types of gum formation occur.
The one is that occurring in the cambial tissues which results in
the formation of the gum pockets; and the other, that which
occurs in the cortical tissues resulting in the formation of the
bark excrescences, the stained terminal branches and the
marked fruit. In the former, free gum is formed and whole
cells are broken down and become a part of the gum mass; in
the latter, the gum occurs principally as cell occlusions. The
former is developed in young .developing stems; the latter is de-
veloped in older tissues that are nearing maturity.
In this experiment, the seeds were planted on a nutrient agar
media and allowed to grow about one month. In that time the
seeds germinated and the stems made a length growth to where
the second pair of leaves were beginning to develop. Judging
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Florida Agricultural Experiment Station
,i ( [/
- ehCt, I
( i \, \ I k
Ni ~H1k I~ Lf(\
i. ) ~ ~ 1~
FIG. 4.-Citrus seedlings showing the influence on root development
of nutrient media containing vanillin in various concentrations
from 39 to 5000 parts per million. The longer roots in the 2500
ppm. media were produced in breaks in the agar media made by
drying out. They did not penetrate the media at all.
32R
Annual Report, 1916
from the time of development of gum formation in the cortical
tissues of Dieback tree, it was not expected that any gum
formation would show in the cortical tissues of these seedlings,
but it was thought possible that gum formation might occur in
the cambial tissues. The gum might or might not be evident
to the naked eye, but it would show in microscopic sections.
(Fla. Agr. Exp. Sta. Rep., 1912, p. cv.)
Free hand sections were made of all plants in the experi-
ment, and no evidence of gum formation could be found, altho
the development of the plants, particularly those grown in nu-
trient media containing 5,000 and 2,500 ppm. of vanillin indi-
cated plainly a toxic effect. The results are not conclusive be-
cause it is not known that gum formation will occur in tissues
of this type at this age. It has not been observed in the field
in plants less than one year old. However, neither observation
nor experiment has been sufficiently extensive to say definitely
that it will not occur in tissues of this type and age.
PLAN OF THE EXPERIMENT.-The plants were grown under
sterile conditions in long homeopathic vials of about 25 cc.
capacity. A complete nutrient media containing 2 percent agar
and 25 ppm. of nitrogen was used as a growth medium. A low
strength of nitrogen was used with the idea that the plant
would absorb the vanillin more readily.
The nutrient media was made up in the following propor-
tions:
Magnesium sulphate ...................................... .25 gram
Mono-potassium phosphate ............. ................... .50 gram
Mono-calcium phosphate ...................................... .50 gram
Potassium sulphate ................-.......................--- .25 gram
Sodium nitrate ........................................... .15 gram
Ferric chloride .............................. ... ............... 01 gram
Distilled water ...-.........................................1.00 liter
There were ten series included in the experiment in which
eight different strengths of vanillin, varying from 39 to 5,000
parts per million were used. The media for each series was
made up separately. Equal amounts of the double strength nu-
trient media and double strength vanillin were mixed, and
sufficient agar added to make 2 percent. The lots were heated
in the autoclave and funnelled into vials. About 10 cc. was
placed in each vial. The vials were then plugged with cotton
and sterilized for 15 to 20 minutes at 15 lbs. pressure.
Grapefruit seed fresh from the fruits and soaked two days
in water were used for planting. The seed selected were uni-
form in size. They were sterilized during four hours in a solu-
3
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Florida Agricultural Experiment Station
tion of 14 grams of chloride.of lime in 140 cc. of distilled wate
(Wilson, J. K. Am. Journ. Bot. 2:420-427, 1915.) The see
were transferred immediately from the solution to the vials b
means of a spoon and with the usual care necessary to avoi
contamination. Two seeds were planted in each vial. Ten c
more vials were included in each series.
The experiment was constituted as follows:
Series I Nutrient solution alone.
Series II Nutrient solution plus nitrate of soda to make
100 ppm. of nitrogen.
Series III Nutrient solution plus vanillin 5000 ppm.
Series IV Nutrient solution plus vanillin 2500 ppm.
Series V Nutrient solution plus vanillin 1250 ppm.
Series VI Nutrient solution plus vanillin 625 ppm.
Series VII Nutrient solution plus vanillin 312 ppm.
Series VIII Nutrient solution plus vanillin 156 ppm.
Series IX Nutrient solution plus vanillin 78 ppm.
Series X Nutrient solution plus vanillin 39 ppm.
RESULTS.-The seed were planted on May 31 and the exper
ment was closed on July 1. During this time, all of the see
had germinated. The stems had attained such lengths th,
many of the tips were touching the cotton and in some cast
beginning to force their way out between the cotton and tI
wall of the tube. The roots, where the character of the media
permitted, were curling in the bottom of the tube. Many of tl
plants had shed their seed leaves. The root tips began to a]
pear at the end of two days after planting; at the end of
week, practically all seed had germinated. Those that had no
dlid not germinate later.
The first indication of toxic action, was the inability of ft
roots to penetrate the media. This occurred in the series whei
concentrations of 156 ppm. and above were used. Later, tl
roots in the series of all concentrations up to and including th;
of 1,250 ppm. penetrated the media, but made increasingly slo
growth from the lower to the higher concentrations.
The roots in all series where vanillin was used, were di,
colored from a purplish-brown to a brown color to a short di
tance above where they were in contact with the media. Th
color was most pronounced near the surface of the media. A
the tips dipped deep into the media, the coloration was lei
intense; in some cases the regions back of the tips were almo
white.
This coloration was due to injury to the epidermal and tl
sub-epidermal cells. In the concentrations from 1,250 ppr
upward-the injury extended much deeper into the tissue-i
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Annual Report, 1916
some cases killing it into the phloem region. With later growth
a cork cambium was formed, cutting off the dead tissue which
gave the root surface a rough flaky appearance.
A marked discoloration was evident in the xylem region, par-
ticularly in the higher concentrations. In the lower, concentra-
tions the sections, made after the experiment was closed, showed
discoloration only in that part of the xylem lying adjacent to
the pith. The remainder of the xylem was normal in appear-
ance. The xylem discoloration extended only to a short dis-
tance into the stem.
Cross-sections made at intervals from the tips of the roots
to the tips of the stems of plants in all series failed to show
any indication of gum formation. The xylem tissue laid down
by the cambium, even beneath the points where the greatest
injury had occurred in the cortical region, was complete and
without break.
NOTES ON PLANTS IN SERIES.-Series I.-The plants made a
normal growth. The roots penetrated the media well, and curled
in the bottom of the tube, but they were rather slender. The
stems were somewhat slender-particularly as compared to
those in the next series.
Series II.-The plants in this series made an excellent growth.
The roots and stems were long and strong. These were by far
the best plants in the experiment. Since the only difference
between this and Series I was the amount of nitrogen contained
in the media, it is indicative that 25 ppm. of nitrogen was not
sufficient for making the best growth and that 100 ppm. was
much nearer the optimum.
Series III and IV.-The plants in these series showed the
greatest amount of injury from the vanillin. The roots failed
to penetrate the media and became very much thickened and
knob-like, where the tips were in contact with the media. New
tips were put out back of the dead ones, which were in turn
killed. The mass had a stubby finger-like appearance.
Marked injury to the cortical tissues was evident. This tissue
was later cut off by a cork cambium, giving the surface a rough,
flaky appearance. Later in the experiment, where the agar be-
gan to break from drying out, fresh root tips were put out
that quickly grew the length of the break, but were injured
when they came in contact with the media.
The stems made a sho-t but apparently normal growth. Evi-
dently the poison did not affect the top growth directly, as is
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Florida Agricultural Experiment Station
the case where a plant is injured by a strong poison such as
a soluble salt of heavy metals.
Since the injury to the roots is so marked, and all evidence of
direct injury to the tops, such as any spotting or killing of the
tissues, is absent, it is indicative that the poison is one that
produces only local injury, and that its direct effect is not ex-
tensive as is the case of a strong poison such as mercuric
chloride.
Series V to X.-The plants in these series made a growth
somewhat comparable to that of the plants in series I. The
tops showed no direct injury. The stems and roots were some-
what shorter in the higher concentrations.
The roots were slow in penetrating the media having, a con-
centration of 156 ppm. upward. However, finally, all roots
penetrated, grew thru the media and curled in the bottom of
the tube. The roots in 156, 312 and 625 ppm. vanillin showed
more or less surface injury, especially on the large roots. This
was much more marked on the plants in the 1250 ppm. vanillin
media. The roots in all of the series were discolored where in
contact with the media.
CONCLUSIONS.-No gum was formed in the grapefruit seed-
lings by the toxic action of vanillin under the conditions of this
experiment. However, this does not prove that it may not be
formed in the tissues of older plants or under other conditions.
Marked injury to the roots was produced by the vanillin
without producing any spotting or killing of the tissues in the
stem. This is indicative that vanillin cannot produce injury
to the same extent as does mercuric chloride, which can produce
widespread injury and gum formation in older citrus plants.
EFFECT OF VANILLIN ON CITRUS CUTTINGS
The following experiment was carried out to determine
whether or not vanillin would induce gum formation in cuttings
from citrus trees. The experiment was carried out in a com-
plete nutrient solution containing different concentrates of va-
nillin. One of the checks consisted of the nutrient solution plus
100 ppm. of copper sulphate. This chemical is known to pro-
duce gum formation readily in citrus trees. It was, therefore,
presumed that it would do so here, if the conditions of the
experiment were right for gum formation.
Fresh cuttings of immature and mature terminal branches
were obtained from a rapidly growing nine-year-old pineapple-
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Annual Report, 1916
orange tree on sour stock. The immature cuttings were an-
gular branches that had not completed their length growth and
were in a succulent condition. The mature cuttings were
branches that were produced the preceding (spring) flush of
growth and were well matured. The stems were more or less
rounded.
The branches were cut from the tree and immediately' im-
mersed in water. In the laboratory, they were cut under water
before being used in the experiment.
The nutrient solution and the concentrations of vanillin were
the same as those used in the experiment with citrus seedlings,
which has just been described. (The effect of vanillin upon
citrus seedlings). No agar was used nor were the solutions
sterilized.
Three hundred cc. Erlenmeyer flasks containing 200 cc. of the
solution were used for holding the cuttings. Five flasks were
included in a series, and two cuttings-a mature and an imma-
ture one-were placed in each flask. The experiment was car-
ried out in a moist glass chamber erected in the laboratory.
The experiment consisted of the following series:
Series I Complete nutrient solution.
Series II. Complete nutrient solution plus sufficient nitrate of
soda to make 100 ppm. of nitrogen.
Series III Complete nutrient solution plus copper sulphate 100
ppm.
Series IV Complete nutrient solution plus vanillin 5000 ppm.
Series V Complete nutrient solution plus vanillin 2500 ppm.
Series VI Complete nutrient solution plus vanillin 1250 ppm.
Series VII Complete nutrient solution plus vanillin 625 ppm.
Series VIII Complete nutrient solution plus vanillin 312 ppm.
Series IX Complete nutrient solution plus vanillin 156 ppm.
Series X Complete nutrient solution plus vanillin 78 ppm.
Series XI Complete nutrient solution plus vanillin 39 ppm.
The experiment was begun June 24, and was closed June
27. In studying the formation of gum in plants in the
field by placing chemicals beneath the bark, it was found
that it usually required from 36 to 48 hours for the first indi-
cation of gum formation to show. (Fla. Agr. Exp. Sta. Rep.,
1913, p. xxx.) It was therefore considered that from three
to four days should be quite sufficient time for gum develop-
ment in the cuttings.
RESULTS.-The cuttings were without change in gross ap-
pearance until the beginning of the third day. No wilting had
occurred and the leaves were more or less tinged. On the
morning of the third day much wilting and defoliation was
evident in all of the cuttings except those in the nutrient solu-
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Florida Agricultural Experiment Station
tion without copper or vanillin. No indication of gum forma-
tion was evident to the unaided eye.
Cuttings were selected from the series and sections made to
note for the presence of gum cycles. None were found.
On the morning of the fourth day practically all of the cut-
tings in all of the series were defoliated. The succulent cut-
tings were badly wilted and dying. Cuttings were again se-
lected and sectioned for study. No gum cycles were found.
Since no gum was found in the cuttings of the check series
containing copper sulphate, and since the chemical is known to
produce gum formation readily, it is to be concluded, either that
copper sulphate at this concentration cannot induce gum forma-
tion, or that gum formation is impossible in the cuttings. Gum
formation is known to be a function of active, growing cells.
The more rapid the growth the greater is the gum formation.
It is possible that the lack of gum formation in the cuttings is
due to absence of growth.
INJURY TO CITRUS TREES BY GROUND LIMESTONE
The attention of the Experiment Station has been called to a
number of groves in which the use of ground limestone has
apparently led to injury. This injury showed itself by a
marked frenched or chlorotic condition of the foliage. With late
development there was lack of growth, much defoliation, a de-
velopment of multiple buds, and a hard dry appearance of the
bark, giving the tree a general starved appearance. The roots
showed evidence of injury by the presence of very few live
feeding tips. Apparently the regions back of the fibrous roots
were in a healthy, normal condition.
That ground limestone should be suspected of inducing injury
under any condition has occasioned much surprise among the
growers. The general impression has been that it was a nat-
ural product which under all conditions was not only entirely
harmless but was highly beneficial to plant growth. From grove
observations and field experiments there is strong evidence in-
dicating that under certain limited conditions ground limestone
may induce injury to young citrus trees in Florida.
That injury may occur to plants from the presence of ex-
cessive calcium carbonate (lime) in the soil has long been
known. Certain plants are much more susceptible to such in-
jury than others. Frear, in a review of the literature on the
liming of soils (Sour Soils and Liming, Dept. Agr. Penn. Bul.
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Annual Report, 1916
261, p. 45), calls attention to a number of plant diseases caused
by an excess of calcium carbonate in the soil.
Grapes growing upon certain limestone soils in France often suffer from
chlorosis, a white spotting of the leaf, associated with great depression in
the vigor of the plant.
Other plants also than the grape became chlorotic under like influences.
G. Riviere and G. Bailhache observed that excess of calcium carbonate in
soil is attended by chlorosis of pears grown upon quince stocks, and that a
chlorotic appearance occurred when no more than 4 percent of the carbonate
was present; and that the attack was conspicuous with 17 percent of the
carbonate, and with 28. percent death ensued.
P. Maze, Ruot and De Moigne observed that the addition of 0.2 percent
of calcium carbonate to a water culture in which Vicia narbonnensis was
flourishing, causes chlorosis, also that the white lupine and the vetch became
chlorotic in the presence of an excess of calcium carbonate to which corn
was resistant; but Maze caused chlorosis of corn by keeping the excess of
lime carbonate, but diminishing the iron and sulphuric acid in the nutrient
solution."
Gile (Porto Rican Exp. Sta. Bul. 11) reported the failure of
pineapples with the appearance of chlorosis (frenching) on cer-
tain areas of the Island where there was an excessive amount
of calcium carbonate in the soil. He made an extensive study
of the problem in the course of which numerous experiments
were carried out and many analyses made. He found that for
ordinary sandy soils, about 2 percent of calcium carbonate -en-
ders them unsuitable for pineapples. Smaller amounts than
this did not appear to be injurious. On the other hand, soils
containing as high as 40 percent of calcium carbonate but com-
posed principally of organic matter produced vigorous plants.
He was able to produce the trouble readily on sandy soil by the
addition of lime in quantity to the soil. He concluded that lime
reduced the availability of the iron in the soil, so that the
plant absorbed an excessive amount of calcium and an insuf-
ficient amount of iron. This reduced the ability of the plant to
form chlorophyll, which in turn led to further injury and finally
to the death of the plant.
An interesting point in the development of the trouble in the
field and in the greenhouse was that the plants, after being set
out, grew normally thru a period of several months before they
developed the diseased condition.
The root system of the chlorotic plants showed no evidence of disease.
The roots differed from those of normal plants in being somewhat larger and
not so thick; they were more like those of plants suffering from starvation.
The plants, however, that suffered from the chlorosis for some time had
many dead roots, but the functioning roots appeared to be perfectly healthy
and an examination by the pathologist failed to show any bacterial or fungus
trouble."
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Florida Agricultural Experiment Station
FIG. 5.-Citrus tree around which ground limestone was used.
DREW GROVE
The first case of apparent injury from ground limestone to
come to the attention of the Experiment Station was that in the
grove of W. L. Drew of Winter Haven. In September, 1913,
he addressed the Director of the Experiment. Station as follows:
I have had an unexpected experience in causing frenching by the use of
ground limestone...... I have at Winter Haven, my own grove of 25 acres,
and joining it I have charge of my brother's grove of 16 acres. Twenty-
eight rows of trees in this latter grove are Duncan grapefruit. Each row
contains nineteen trees. Fourteen rows are on rough lemon roots and four-
teen on sour orange roots. These trees were set in December, 1910. The
trees of the two adjoining rows, the last row on rough lemon and the first
row on sour orange, were set in soil with which there had been mixed a
liberal quantity of ground limestone. No lime of any kind has, up to the
present time, been used in any other portion of the grove. The trees where
the limestone was used showed no difference in growth or appearance from
the other trees during the first summer-the summer of 1911.
On May 10, 1912, we scattered a liberal quantity of the ground limestone
around the trees of these two rows and all over the middle between the two
rows. In the summer of 1912 we failed to observe any effects of the ground
limestone in the trees that were on rough lemon roots. The trees of the
Annual Report, 1916 41R
row on sour orange seemed to be growing a little faster and looked a little
thriftier than the remainder of the trees on that root. I did not see the
trees from September, 1912, to July, 1913. At this time both of these treated
rows showed a large amount of frenching in great contrast with the trees
on either side that showed almost none at all. I took three men at different
times out to see the grove and telling them of this experience with ground
limestone asked them to point out the rows. This each one did, without
hesitation, long before he had reached them.
The grove is situated on good average high pineland of the Winter-
haven section. All of the trees have had the same care and fertilizer from
the first. As there is no difference in the character of the land where these
two rows are, it is evident that the limestone has caused the frenching. It
may be that where limestone is used, a fertilizer of a different character
should be used. I can hardly believe that the lime itself has been injurious
and so I suspect it to be the lime and the fertilizer combined.
"..... Beggarweed is the cover crop in this grove. I might add as a
result of this experiment, and another previously made, that it is clear that
on this land, where no fertilizer was applied, beggarweed is not benefited
by an application of ground limestone. I hesitate to state that it has been
injured but such seems to be the fact. There are spots all over both of
these groves where the beggarweed frenches and does not grow well, at
least in the absence of fertilizer, and this condition seems to be more pro-
nounced where ground limestone has been applied."
If
I* ":; *. '....,.:.*
I - < .',' :"' .*, .' "'?
FIG. 6.-Citrus tree around which ground limestone was not
used. Tree is of same age, same variety, on same stock
and in adjoining row to one shown in fig. 5.
Florida Agricultural Experiment Station
FIG. 7.-View in citrus grove of middle over which ground limestone has
been spread. Trees to left on sour stock. Trees to right on rough lemon
stock. Note absence of cover crop.
SUBSEQUENT HISTORY OF GROvE.-Since September, 1913,
when this letter was written, the trees in the two rows have
made slow growth. Their appearance has varied with the sea-
son. At all seasons the marked frenched condition has prevailed
more or less. In the winter of 1915, they had a general starved
appearance. The type of growth which had developed was quite
different from that of the trees in the adjoining rows. Instead
of general growth all over the tree, it was somewhat confined
to rather strong shoots toward the center of the tree. These
had made more or less of a straight lengthy growth, giving the
tree a rather upright type of growth instead of a compact
spreading type that characterized the trees in the other rows.
A general lack of foliage gave the trees a very open appear-
ance. The frenching and defoliation occurred more toward the
tips of the branches. The tip leaves were often completely yel-
low. The leaves toward the base of the branches were more
plentiful and had a somewhat normal size and color. Multiple
buds were more or less plentiful on many of the short terminal
branches. These branches were frequently completely defoli-
ated. The bark of the large branches and of the small ones
a year or more old had a rather hard dry look. The fibrous
roots were brown and dead. Very few live ones could be found.
The main roots appear to be alive and normal.
The difference between the cover crop between the two rows
and in the remainder of the grove was very noticeable. Be-
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Annual Report, 1916
FIG. 8.-View in citrus grove of middle adjoining one shown in fig. 7. No
ground limestone has been applied. The trees of both rows are on sour
stock. The row on the right is the same as row on the left in fig. 7.
tween the two rows, it had evidently been very sparse, whereas,
in the remainder of the grove it was more or less plentiful. In
the former the plants had come up, made a little growth, turned
yellow and died; in the latter they had made complete develop-
ment. Cowpeas had been planted between the two rows but had
made very little growth.
In April, 1916, the trees had put out some new growth that
gave them an improved appearance. The old foliage and some
of the new showed frenching. The abnormal condition still ex-
isted in the soil. At the end of a period of ten days during
which no cultivation had been done on account of a rain, the
volunteer cover crop seedlings were coming through the soil
very plentifully in the grove; very few were evident in the area
between the affected trees, except at one end where some stable
manure had been applied during the spring of 1915.
FERTILIZER TREATMENT.-The fertilizer given the two rows
was the same as that given the remainder of the grove up to
August, 1913. It was as follows:
March, 1912 .... ..--6 from sulphate of ammonia, sulphate of
potash, dissolved bone black, blood and
bone tankage, about 1 lb. per tree.
June, 1912.... -......... ........4. 4-6-6 from same sources, about 1 lb. per tree.
August, 1912 .... .. ... .........4-6-12 from sulphate of ammonia, sulphate of
potash, and acid phosphate, a little over
1 lb. per tree.
February, 1913 ...... .... 5-6-6 from sulphate of ammonia, sulphate of
potash, and dissolved bone black, a little
over 2 lbs. per tree.
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Florida Agricultural Experiment Station
June, 1913.................................5-6-5 from nitrate of soda, sulphate of ammo-
nia, tobacco stems, steamed bone flour,
dissolved bone black, and sulphate of
potash, about 2% lbs. per tree.
August, 1913 (except trees
1 to 9 in both rows).......... 5-6-5 from the same sources, 2 lbs. plus per
tree.
From August, 1913, to January, 1915, the fertilizers applied
were as follows:
October 16, 1913..................Trees 1 to 9, both rows (not fertilized August,
1913), 31/ lbs. each of Painter's Dieback
Fertilizer of formula 8 percent phos-
phoric acid.and 13 percent potash.
December 13, 1913..................All trees, 2 lbs. per tree of formula 3-6-13
from sulphate ammonia, acid phosphate,
and double manure salts.
March 26, 1914......................All trees, 2 lbs.- per tree of formula 4-6-6
from nitrate of soda, sulphate ammonia,
acid phosphate, ground steamed bone,
and sulphate of potash.
June 18, 1914......................... All trees, 4 lbs. per tree of formula 4.25-6-12
from nitrate soda, sulphate ammonia,
ground steamed bone, low grade sulph-
ate of potash and floats.
In January, 1915, the two rows were divided into plots and
fertilized according to a plan outlined by a fertilizer representa-
tive. The treatment was as follows:
January 2, 1915....................Trees 1 to 4, both rows, 6 lbs. per tree of for-
mula 3-6-10 from nitrate soda, sulphate
ammonia, dried blood, acid phosphate
and sulphate of potash.
Trees 5 to 7, both rows, 6 lbs. per tree of a
fruit and vine brand.
Trees 8 to 10, both rows, 9% lbs. per tree of the
mixture: 4-12-6 from sulphate ammo-
nia, dissolved bone black and sulphate
potash ........... ..... .. ...... ....... .......27 lbs.
Copperas .................. ......... ........... 3 lbs.
Goat manure.................................30 lbs.
Trees 11 to 13, both rows, 9% lbs. per tree of
the mixture: 3-10-6 frpm sulphate am-
monia, nitrate soda, dried blood, acid
phosphate and sulphate potash......37 lbs.
Copperas ......................... ......... 3 lbs.
Trees 14 to 16, both rows, 131 lbs. per tree of
the mixture: Hardwood ashes......25 lbs.
Copperas ..... ........- ............... 4 lbs.
Steamed bone.... ........ -............. 25 lbs.
Goat manure ............ ..........-...25 lbs.
Nitrate soda........... ......................-- 3 lbs.
Trees 17 to 19, both rows, 11 lbs. per tree
of the mixture: Steamed bone....30 lbs.
Copperas .....-................. ....... ....... 3 lbs.
Goat manure ...... ...- .... ............... 30 lbs.
Nitrate soda .................. .............. 3 lbs.
In March, 1915, only a part of the trees were fertilized. The
plan as outlined in January was discontinued on account of the
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Annual Report, 1916
unfortunate death of the fertilizer company's representative.
The fertilizer applied in March was:
March 11, 1915........................Trees 1 to 4, both rows, 6 lbs. per tree of for-
mula 3-6-3 from sulphate ammonia, ni-
trate soda, acid phosphate, goat manure,
tobacco stems and potash.
Trees 5 to 7, both rows, 6 lbs. per tree, a fruit
and vine brand.
Trees 8 to 19, both rows, not fertilized at this
time. Expected to continue experiments
but stopped on account of death of rep-
resentative.
About this time a light application of stable manure was
spread over the area between the first two trees of both rows.
A cover crop developed quickly over the area but the applica-
tion was apparently without benefit to the trees.
From June, 1915, to April, 1916, all of the trees were fer-
tilized alike, as follows:
June 23, 1915 .................. All trees, 6 lbs. per tree of Painter's ammoni-
ated Dieback fertilizer.
December 31, 1915 ...........All trees, 7 lbs. per tree of formula 3-8-2 from
sulphate ammonia, acid phosphate,
ground tobacco stems and goat manure.
February 10, 1916.............All trees; 4 lbs. per tree of formula 4-8-0 from
nitrate soda, sulphate ammonia, and
acid phosphate.
April 15, 1916-.......... .......All trees, 4 lbs. per tree of formula 4-8-0 from
sulphate ammonia and acid phosphate.
DIscussION.-Since, up to the time that the injury was first
noticed, the only difference in treatment between the two rows
and the remainder of the grove was the ground limestone ap-
plied, and since soil conditions are practically the same where
they were planted as in the remainder of the grove, it seems
quite evident that the ground limestone has been the direct or
indirect cause of the injury to the trees. How the limestone has
induced the injury is a matter of conjecture. The wide use of
ground limestone in the citrus groves of Florida without any
apparent injury and with apparent benefit indicates that the
injury can occur only under very special conditions. The con-
ditions prevalent in this grove must be an indication of the
conditions necessary for the development of the trouble. A
cursory review of these showed that the tendency of the soil to
dryness and the lack of humus were probably the chief abnor-
mal conditions present. The grove practices are such that the
humus supply would not be conserved or increased. The inti-
mate mixture of the ground limestone with the soil in the holes
where the trees were planted is probably another factor in the
development of the injury.
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Florida Agricultural Experiment Station
The greatly increased growth of the trees on the sour stock
receiving the ground limestone over those on the same stock
not receiving it indicates that the first effect of the limestone
was to bring about a soil condition that was stimulating to
growth. This was followed by a condition that was conducive
to injury not only to the trees but also to the cover crop.
The application of the manure in 1915, enabling the cover
crop to grow readily, is indicative that the injury of the trees
may be due to a lack of bacteria in the soil.
The application of the organic sources, dried blood and goat
manure, in connection with the plot treatments in January,
1915, did not bring about any marked increase of the cover
crop. Therefore it is probable that the stable manure was valu-
able more on account of the bacteria that it added to the soil
than on account of the organic matter added.
This same appearance of the trees and lack of growth of the
cover crop has been observed in other groves where limestone
was not used but where the soil had apparently been injured by
excessive cultivation. Such injury has not been observed ex-
cepting in groves planted on dry sandy lands lacking in humus.
Where such injury has occurred the limiting of cultivation to
the spring season, the adoption of grove practices that build
up the soil, and severe pruning have brought about a recovery
of the trees.
OTHER GROVES
In a number of other groves where ground limestone has been
used the same type of injury to the trees and to the cover crops
has developed. All of these groves were planted on dry, sandy
lands lacking in humus. None of the trees was more than seven
to ten years old. Injury to the trees followed a period of nor-
mal growth. The first indication of injury was frenching. This
was followed by the development of' a general starved appear-
ance in spite of the fact that the trees were well fed. However,
in these groves it was very difficult to trace the injury to the
ground limestone because it had been applied uniformly over
the groves. No part was left without it. If ground limestone
can cause injury to citrus trees it probably has done so in nu-
merous cases in the past, but the connection has been over-
looked thru attributing the injury to other causes or thru a
lack of checks for comparison.
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Annual Report, 1916
EXPERIMENTAL GROVE, TAVARES
The Experiment Station has a fertilizer experiment at Ta-
vares, Florida, in cooperation with Mr. G. M. Wakelin (Fla.
Agr. Exp. Sta. Rep., 1909, p. xxvii). There are 47 plots re-
ceiving fertilizer treatment and one plot without fertilizer. Of
these there are three that have received ground limestone in
addition to the fertilizer. The limestone was applied first soon
after the trees were set out in January, 1909, and at irregular
intervals since. Each application consisted of 10 pounds per
tree. During the first few years after the experiment was
started frenching was general thru the grove on account of the
presence of Dieback in the trees. During the year 1915 the
trees had mostly recovered from the Dieback conditions and the
plots showing frenching stood out in more or less marked con-
trast to the remainder of the plots.
Five plots showed a severe attack of frenching (Fla. Agr.
Exp. Sta. Rep., 1915, p. c). The fertilizer treatments given and
the order of severity of the attack is as follows:
Plot 21 ............5-6-6 formula from cottonseed meal, acid phosphate,
sulphate of potash with ground limestone.
Plot 11.....-.........5-6-6 formula from sulphate of ammonia, acid phos-
phate, and sulphate of potash with ground lime.
stone.
Plot 30...--........-5-6-6 formula from nitrate soda, acid phosphate, and
hardwood ashes.
Plot 28..............5-12-6 formula from nitrate soda, Thomas' slag, sulphate
of potash
Plot 39...............5-6-6 formula from sulphate of ammonia, acid phos-
phate, and sulphate of potash with ground lims-
stone.
Plot 21, where the ammonia of the fertilizer applied was de.
rived from cottonseed meal and ground limestone was .used as
a soil addition, shows by far the greatest amount of frenching.
During the winter of 1915 the foliage on these trees became
quite yellow and there was much defoliation.
None of the trees in the frenched plots was as markedly in-
jured as the trees in the Drew grove. However, here no ground
limestone was mixed in the holes where the trees were planted.
In the summer of 1916 the trees through the whole grove had
put on a good growth and all except the trees in the frenched
plots showed a more or less normal color. Frenching was still
persistent in plots 21, 11, 28, and 39. Plot 30 had recovered
and showed very little yellowing. But plot 20, which received
the same fertilizer treatment (5-6-6 from cottonseed meal, acid
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Florida Agricultural Experiment Station
phosphate and sulphate of potash) as plot 21, but without the
ground limestone, now showed a marked case of frenching.
It is thus seen that all of the ground limestone plots in this
grove, in addition to some others, showed injury.
POT EXPERIMENTS WITH GROUND LIMESTONE
As a part of other experiments in the greenhouse, the fol-
lowing pot experiment was carried out, using ground limestone
in pure sandy soil and without fertilizer. The purpose was to
determine the effect of the limestone upon the plant in the ab-
sence of other materials (such as fertilizer) which might inter-
fere with its action. Under the conditions of the experiment
it was to be expected that the plants would show the effect of
starvation as the soil used was a pure sand almost without
organic matter and therefore lacking in the food elements.
Grapefruit seed were planted -in the pots on February 8, 1915,
and allowed to grow until about June 22. At this time the
plants were free from the seed and entirely dependent upon the
sand for food. Five pots were included in a series and five seed
were planted in a pot. The sand used was a coarse sand from
the shores of Lake Weir in Marion county. The pots were six-
inch pots, the walls of which had been soaked in paraffin. The
experiment was carried out on the east bench of the greenhouse
under uniform light conditions and under as nearly uniform
moisture conditions as the average greenhouse watering will
allow.
The series and their treatment are as follows:
Series I ...............Ground limestone.... .....-........- 48 grams
Series II ................Ground limestone...................- 32 grams
Series ITT .............. Ground limestone......-............24 grams
Series IV ................Ground limestone---....................16 grams
Series V ..........-..-Ground limestone...............12 grams
Series VI ...--..........Ground limestone.................... 8 grams
Series VII --.............Ground limestone.................... 4 grams
Series VIII................Ground limestone............. .. 2 grams
Series IX ................Ground limestone ................... 0 grams
The ground limestone was well mixed with the sand before
placing it in the pot.
RESULTS.-Table 14 shows the results of measurements made
upon the plants when the experiment was closed late in June,
1915. From these, it is evident that the plants of all series
excepting I and II made a growth that was no better than that
of series IX which received no limestone. The plants of series I
and II made on the average 7 and 11 percent greater growth
48R
Annual Report, 1916
SI I
,J *-
I ii
\ r
tI
FIG. 9.-Pot experiments with ground limestone. No. I, grown in sand to
which 48 grams of ground limestone had been added. No. IX, grown in
sand without the limestone.
respectively than the plants of series IX without limestone.
This increase is comparatively small.
The most marked difference between the plants receiving
ground limestone and those not receiving it was in the leaf color
and in the root development. The plants of Series I to VI in-
clusive showed marked frenching with a yellowish-green back-
--- 1
49R
01
;- ;r 71 'i f ~ Y 9
5OR Florida Agricultural Experiment Station
ground. There was very little variation among the different
series.. The plants of series VII and VIII showed only traces oi
frenching. The plants of series IX were entirely free frorr
frenching but had the yellowish-green color indicating at leasi
nitrogen hunger.
There was an appreciable difference in root development be-
tween the plants receiving ground limestone and those not re-
ceiving it. This difference was noticeable even where only twc
grams of limestone were used per pot, but was more pronounced
where the larger amounts were used. The roots in all cases
were slender but were longer and more profusely branched in
the limestone series. All roots, with the limestone as well as
without the limestone, appeared normal. No dying of the tops
was evident.
TABLE 14
POT EXPERIMENTS WITH CITRUS SEEDLINGS.
Series Stem Stem Leaf Leaf Fresh Dry
No. Length Diam. Length Breadth Weight Weight Av.
A B A B A B B A B A B
I ............- 58.3 124 2.3 105 30.9 101 15.1 94 1.27 122 .41 121 111
II .................. 54.1 114 2.3 105 30.5 100 15.8 99 1.17 113 .38 112 107
III ................. 54.5 115 2.3 105 29.3 96 15.1 94 .98.1 94 .32 94 100
IV ........ 49.8106 2.2 100 29.4 96 15.4 96 .93 89 .30 88 96
V ................... 50.4. 107 2.2 100 29.3 96 15.0 94 1.00 96 .32 94 98
VI ..-........ 52.9 1112 2.2 100 31.0 102 15.1 94 1.10 106 .34 100 102
VII -............. 47.5 101 2.21100 29.9 98 15.3 96 1.02 98 .33 -97 98
VIII ........... '49.7 105 2.2 100 28.8 94 14.7 92 1.04 100 .32 94 97
IX ..-.....--..- 47.2 100 2.2 100 30.5 100! 16.0 100 1.04 100 .34 100 100
A.-Average measurements in millimeters.
B.-Relative measurements (check series, 100).
GENERAL CONCLUSIONS.-It seems quite evident that ground
limestone can, under limited conditions, induce injury to citrus
trees, and that this injury will show itself by a frenching (a
form of chlorosis) of the foliage of the trees.
* How the ground limestone can induce this injury is still a
matter of conjecture.
Respectfully,
B. F. FLOYD,
Plant Physiologist.
Annual Report, 1916
REPORT OF THE ENTOMOLOGIST
P. H. Rolfs, Director.
SIR: I submit herewith my annual report for the fiscal year
ending June 30, 1916.
VELVET BEAN CATERPILLAR
(Anticarsica gemmatilis)
The study of this pest was continued by making further in-
vestigations of its migrations, natural enemies, and especially
the moths' preferences among the different species and varieties
of Stizolobium. The results of this work, as well as that of
previous years, have been collected into a bulletin, "Life His-
tory of the Velvet Bean Caterpillar," which is now in manu-
script. A more practical dust for the control of this insect was
developed. This has been included in Bulletin 130 which has
been published.
The attempt to establish Calosoma sycophanta was not suc-
cessful. The beetles remained active until the rainy season
set in. They then began to appear above ground less frequently
and to refuse food. They finally passed into complete aestivation;
most of them died, and the remainder did not become active
again until the following spring. Not one egg was observed.
Apparently the insect is not adapted to the climatic conditions
of Florida.
FLORIDA FLOWER THRIPS
Most of the time spent in studying this insect was given to
(1) its seasonal history, especially its manner of spending the
winter, and the reason for its greater abundance in dry weather,
and (2) the extent of its damage to citrus.
HIBERNATION
In addition to a careful watch of the insect in the field, indi-
viduals were caught and placed in test tubes closed with cotton
plugs. These test tubes were kept constantly supplied with
fresh food .(rose petals) and were placed in an open-air insect-
ary where they were exposed to the same temperature as in the
open fields. They were, of course, protected from heavy rains.
The test tubes were placed on the north side of breeding cages
made of wire netting. Here they were protected from the
direct rays of the sun, which would have caused a marked rise
in temperature during the middle of the day, yet they were well
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Florida Agricultural Experiment Station
lighted. Most of the thrips placed in these tubes died within
a few days after their introduction but many lived for several
weeks and one individual lived for 59 days. This did not repre-
sent the insect's maximum age as it was doubtless several days
old when caught.
Observations during the winter of 1915-1916 confirmed those
of the previous seasons (see Fla. Agr. Exp. Sta. Rep., 1915, p.
lxvi) that the Florida flower thrips does not breed during the
cooler weather of winter. But on January 5, after a week of
warm weather, a few young were found in one of the test tubes
in the open-air insectary. On the same date, on some 50 roses
examined on the Station grounds, three larvae were found.
During the winter, including the coldest days, thrips were
always found in the rose blossoms even when the latter were
badly frosted. During such weather they were inactive but
would move if disturbed.
Our studies have thus far established that the Florida flower
thrips spend the winter as adults in blossoms, but there may be
some breeding during a warm period in any month of the year.
There are no indications that they ever enter the ground or
seek other shelter than the depths of the flowers. They are
capable of living as adults for at least eight weeks during the
winter. This length of time is sufficient to tide them over the
non-reproductive period as breeding usually continues until
some time in December and begins in late February or March.
HEAVY RAINS VERY DESTRUCTIVE
Ever since the writer has been in Florida, he has noticed that
thrips are much more abundant during and immediately fol-
lowing a period of drouth. During the last year closer obser-
vations have been made to determine the factor responsible for
their disappearance. As many insects in Florida are controlled
during the hot moist rainy season by entomogenous fungi, an
especial search was made for such fungi parasitizing thrips. Al-
tho Microcera-like fungi were occasionally found growing on
dead thrips, there is no evidence that entomogenous fungi are an
important factor in their control. Nor was lack of food the
factor, as thrips would often be greatly reduced in numbers
when there was no corresponding reduction in the number of
available blossoms. On the other hand, after hard, dashing
rains or prolonged rains not especially violent, there was always
a great reduction in the numbers of thrips. For instance, thrips
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Annual Report, 1916
were abundant on roses and other blossoms on the Station
grounds during the early part of December, 1915; but from De-
cember 17 to 20, Gainesville experienced a heavy rain, 4.26
inches falling. On fifty roses examined on December 22, no
thrips were found. Similar observations tho less striking in
results, were made during the summer of 1915. We were able
to get equally striking results with a garden hose when the
flowers were given a thoro drenching. The insects were washed
to the ground and killed. It is evident that prolonged or dash-
ing rains are very destructive to thrips and are the chief nat-
ural factor in keeping down their numbers.
THRIPS ON CITRUS
In the last Annual Report, p. lxviii, we recorded some spray-
ing experiments carried on in the Scott grove at Winter Haven.
The grove was visited again on October 1, 1915, and a count
made of the fruit on the sprayed and unsprayed rows. It did
not differ materially from that made the preceding June as re-
corded in the last Annual Report, but we were able to obtain
better data as to the amount of fruit showing "thrips marks."
In getting the following percentages we counted only those
fruits which showed a sufficiently large area marked to be read-
ily noticeable on the oranges; in other words, those fruits only
which in the hands of a careful grader would have their grade
lowered on account of the markings. Our check rows showed
32 percent of such fruit; sprayed rows only 13 percent.
During the spring of 1916, similar experiments were under-
taken on Pine Island, at Leesburg and at Stanton. The season
was unfavorable for this work, due to the irregularity of the
bloom. Only a few trees in any one grove were in full bloom
at any one time, so that in order to do satisfactory work it
would have been necessary to spray once a week over a period
of nearly two months. Only one grower was willing to do this.
All of the bloom on the Station grounds and most of that in the
Gainesville section was killed by a freeze in February, so that
it was impossible to carry on experiments at Gainesville and it
was necessary to depend upon cooperative experiments. In the
Tillson grove at Leesburg and in the McKenney grove at Stan-
ton several acres were sprayed. Only a few of the trees were in
full bloom. These were carefully marked. On June 28 and
29 these groves were again visited. Because of the small
amount and scattered nature of the bloom at the time the trees
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Florida Agricultural Experiment Station
were sprayed, we could secure no reliable data on the compara-
tive amount of fruit on the sprayed and check trees. In regard
to the amount of scarred fruit more definite data could be se-
cured. In the grapefruit grove at Stanton, 23 percent of the
fruit was sufficiently scarred by thrips to lower the grade in the
hands of a careful grader; the percentage on the sprayed por-
tion was only 9. An adjoining grove of equal age and also un-
sprayed showed 16.5 percent of scarred fruit. Four percent
would probably develop into culls-only.
In the grove at Leesburg, the unsprayed orange trees showed
6.3 percent of scarred fruit. About half of this was badly
marked. The sprayed trees had only 2.7 percent. Some trees
which were just out of bloom when sprayed showed 9 percent
marked fruit.
Altho these results from spraying for thrips are not as strik-
ing as the results from spraying for whitefly and purple scale,
they undoubtedly pay one well for spraying even when the
bloom is unusually irregular and scattering. We estimated that
spraying of 300 trees would result in a saving of at least $15
at a cost not to exceed $6.
THRIPS ON STRAWBERRIES
On April 1, 1916, the entomologist was called to Waldo to
investigate an outbreak of thrips on strawberries. The infesta-
tion was found to be heavy, as many as fifty adults and larvae
being found in a single bloom. These heavily infested blooms
never set fruit but withered and dried up. Others less severely
injured produced deformed, worthless fruits. The production
of the field was being seriously curtailed.
Part of the field was sprayed with a home-made tobacco de-
coction, made by soaking tobacco stems and refuse over night
in enough water to cover them. Three gallons of this solution
and a pound of soap were used to each 15 gallons of water.
This killed all of the thrips reached. As there was considerable
red spider in the other part of the field, the following formula
was recommended:
Home-made tobacco decoction.....-................... ........... ..-.. 10 gal.
Commercial lime-sulphur ~................................ .... 1 gal.
W ater --.. .... ..... -.-.-.-.-.-.- .....- ......... ............. ... 39 gal.
The red spiders were causing much of the damage attributed
to thrips by the growers, such as the production of small, hard
brown berries. However, most of the blasted blossoms and the
54R7
Annual Report, 1916
deformed fruit were caused by thrips. The spraying was en-
tirely successful in controlling the insect.
THE FLORIDA FLOWER THRIPS ATTACKS CAMPHOR
In April, 1916, Dr. E. W. Berger, Entomologist to the Plant
Board, called the attention of the -writer to some camphor trees
in his yard which were being attacked by thrips. Investiga-
tion showed the insect to be the Florida flower thrips and not
the Camphor thrips, altho the character of the damage to the
unfolding buds of the camphor was very similar to that caused
by the camphor thrips (see Fla. Agr. Exp. Sta. Rep.,- 1913,
p. lxvi). This injury is also very similar to that inflicted on
unfolding buds of pears (see Fla. Agr. Exp. Sta. Rep., 1915,
p. lxvii). This discovery will render it necessary to use cau-
tion in concluding that the camphor thrips is present in any
property on the evidence of the lesions in the developing buds
alone. On the trees attacked by the flower thrips there were,
however, none of the bark lesions so characteristic of the work
of the camphor thrips. (loc. cit. p. lxvii and lxvii).
COMBATING NEMATODES BY THE USE OF CALCIUM CYANAMIDE
In the fall of 1914 the attention of the entomologist was
called to the toxic properties of the commercial compound called
Cyanamid" which is a mixture of calcium cyanamide, lime,
charcoal, and other compounds in less amounts. The sugges-
tion was made that it be tried out as a possible spray to control
insects. It seemed that there could be little use as a spray for
such a soluble and toxic compound which would probably burn
the plants to which it should be applied. Upon further reflec-
tion it seemed possible that the compound might be of value in
killing out soil pests if applied before the crop was planted.
The nematode (Heterodera radiciola) seemed to be the most
suitable organism for a trial, as infested soil could easily be
found at any season.
Accordingly, on November 30, 1914, six small plots, each con-
taining three square yards were treated with cyanamid at rates
varying from 3 tons to 200 pounds per acre. The cyanamid
was applied as a top dressing and hoed in. Four similar plots
were used as checks. These were situated on land known to be
heavily infested. On December 4, radishes were planted on
these plots, but a very poor stand was obtained and the plots
were replanted on December 13. On March 18 and., April 20,
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Florida Agricultural Experiment Station
the radishes were gathered. The results of this test are tabu-
lated below.
TABLE 15
EFFECT OF CYANAMID ON NEMATODES IN RADISH BED
Plot Number ........................ 1 2 3 4 5 6 7 10
Dose, pounds per acre..........- 6000 0 3000 0 1600 800 400 0 200 0
Percentage ofplants infested 0 33 0 25, 1 24 5 50 8 33
Weight of radishes in grams 240 260 475 335 780 1015 525 230 670 535
CYANAMID ON RADISHES
Cyanamid, being a strong nitrogenous fertilizer, analyzing
between 20 and 24 percent ammonia, a larger yield on treated
plots was to be expected. The increased yield on the treated
plots is due as much to the fertilizing effect of the cyanamid as
to the vermicidal effect. No other fertilizer was used on any
of the plots. This experiment seemed to indicate that:
(1) Cyanamid used at the rate of 1600 pounds or more per
acre markedly reduced the number of nematodes present; and
(2) If used too strong or applied too near the time of plant-
ing, it inhibits growth or entirely kills the plants.
Altho it would greatly increase the cost of application, it
seemed that the material should penetrate the soil better if
applied in solution. Accordingly a series of plots was laid out
but this time the material was dissolved in water* which was
poured on the surface except on plot F where it was applied dry
and hoed in as in the first series of plots, and then thoroly wet
down. These plots were treated on December 5 and planted on
December 13. The results are shown in table 16.
TABLE 16
EFFECT OF CYANIMID ON RADISHES
Plot ....-- .....--- .................... -A B C D E F Check
Dose in pounds per acre 260 540 1700 3400 5100 5100 0
Percentage infested .... 50 60 6 0 0 0 94
Deleterious effect on
erable dwarfed
growth ....--...........-..... None None None Trace Consid- Plants
Comparing these two tables we find that, contrary to expec-
tations, both absolutely and as compared with the amount in the
*When cyanamid ", the trade name for the impure mixture of calcium
cyanamide, is placed in water, only the calcium cyanamide and some of the
lime dissolves. There is left a black residue consisting largely of carbon.
56R
Annual Report, 1916
check plots, the solutions were not as effective as the dry ma-
terial thoroly mixed with the dry soil and then saturated with
water. All later experiments tend to substantiate this view.
These preliminary tests were so encouraging that during the
spring of 1915 more extensive tests were undertaken and with
the beginning of the fiscal year the subject was included in the
project.
TESTING EFFECT OF CYANIMID ON COWPEAS
In March, 1915, we started experiments with cowpeas on plots
containing a hundredth of an acre each. The large size of these
plots was intended to reduce the danger of the results being
obscured by the migration of the worms from the sides. To
prevent the nematodes being washed over the plots from the
surrounding soil, the plots were ridged so that they were slight-
ly higher in the middle. The cyanamid was applied as a top
dressing and worked in with a disk harrow. The dose varied
from 300 pounds to a ton per acre.
Cowpeas were planted three weeks after the application of
the cyanamid. They did well until dry weather set in when all
of those on the plots that had received 600 pounds or more per
acre showed some burning. On those plots that had received
1400 pounds or more per acre, the cowpeas were not as good
as on the checks. On those plots that had received 1500 pounds
or more per acre there were at first a few knots on roots that
did not extend below a depth of six inches, while on the checks
the roots were knotted to the very crown. Three months later
the nematodes had worked upward so that on the treated plots
also knots began to appear near the surface. Evidently we
had failed to get the material down to a sufficient depth. How-
ever, the plots that had received but 300 pounds per acre showed
fewer knots than the checks. The results of this test are shown
in table 17.
These plots were treated on March 5 and Whippoorwill cow-
peas planted on March 27. They were broadcasted and raked
in. Checks were placed parallel to these plots so there was a
check for each plot.
On the plot receiving 2000 pounds per acre there was not
over 25 percent of the amount of grass and weeds as on the
checks. There was practically no crab grass or Oenothera, both
of which were abundant on the checks. But the seed of coffee-
weed and beggarweed mostly survived the treatment.
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Florida Agricultural Experiment Station
TABLE 17
EFFECT OF CYANAMID ON COWPEAS AND NEMATODES
Dose
per
acre
in lbs.
300
400
500
A
May 2:
Deeper color
than check
Better than
1
Better than
2
appearance of the cowpeas
May 29
Some slight
burning
Some burning
Burned but
not seriously
4 600 Better than More burning
3 not serious
5 800 Better than Burned con-
4 siderably
6 1000 Better than Burned more
5 than 5
7 1200 Nearly as Burned ser-
good as 8 iously
8 1400 Best looking Burned, but
plot still good
9 1600 Dwarfed and Badly burned
burned as com-
ipared with 8
10 2000 Better than Badly burned
check
June 14
Plot
Amount of
Root-knot,
July 12
Much less than
check
Less than 1
Very little
above depth of
6 in.
As 3
As 3
As 3
None above
6 in.
As 7
As 7
As 7
EXPERIMENTS WITH TOMATOES
On April 13, four plots, each 28 by 40 ft., were treated with
cyanamid, 80, 70, 60, and 50 pounds respectively, being used.
This corresponds approximately to doses of 3000, 2600, 2200,
and 1850 pounds per acre. A like plot was left for a check.
Here also the cyanamid was broadcasted and harrowed in. To-
mato plants were set out April 22.
On all of the treated plots the tomatoes were so badly burned
as to be worthless. This burning was not noticeable until a
week or more after the tomatoes had been set in the treated
ground. On the check plot a small crop of tomatoes was har-
vested in spite of the nematodes.
These plots were replanted to a second crop of tomatoes some-
time in August. This time the reverse was noted. The toma-
toes did nothing on the check plot while a fair crop was harvest-
ed from the treated plots. There were some nematodes on all
the plots.
EFFECT OF CYANIMID ON PEACH TREES
On April 9, 1915, we treated five peach trees with a dose
of 6, 4, 3, 2, 1 pounds respectively. The material was scattered
58R
Much better
than check
Better than
1
Better than
2
Better than
3
Better than
4
Better than
5
Better than
6
Again best
looking plot
Not as good
as 8
Badly burned
but better
than check
1
1
Annual Report, 1916
on the ground over a radius of six feet about the trunk of the
tree, and thoroly worked in with a hoe to a depth of two inches.
Two weeks later there were noticeable some wilted twigs on
the treated trees, but this condition was only temporary. Some
weeks later the trees had a greener and more healthy look than
the remainder of the orchard. This was probably due mostly, if
not entirely, to the fertilizing effect of the material. But the
cyanimid did not, as was expected, kill the trees, due undoubted-
ly to the fact that it did not get down to the main roots in the
form of cyanamide, but had gone to urea and nitrates before
reaching the roots.
From these experiments we seemed justified in concluding:
1. That cyanamid applied to the soil greatly reduces the
number of nematodes present.
2. That it does not penetrate the soil readily. It is stated
by agricultural chemists to be quickly absorbed by the colloids
of the soil and then changes to urea and finally nitrates, but
that if heavy doses are used a compound (dicyanamid) is
formed.
The urea and the nitrates resulting from its decomposition
will dissolve in the soil water and penetrate readily so that the
fertilizer effects are marked, even when applied as a top dress-
ing, but the vermicidal effects are not. It will therefore be
necessary to mix the material with the soil thoroly.
3. That if sufficient time does not elapse between the appli-
cation of the material and the planting of the seeds or trans-
planting of the plants, severe damage will result. Furthermore,
that there is a great difference in susceptibility to damage
among plants, tomatoes being very sensitive, and radishes very
resistant.
The problem as it appeared at the beginning of the year was
to determine:
(1) The minimum dose of cyanamid necessary to extermi-
nate the nematodes; or, if complete extermination appears too
costly or impracticable, the dose which will reduce their num-
bers to such an extent as to render it possible to grow profitably
susceptible plants on the land. The question of cost must enter
into all calculations of quantity to be. applied. On a general
farm where the same results can be obtained by growing non-
susceptible crops for three years, the cyanamid method would
be too costly; but on a truck farm or garden, the case is differ-
ent. Here many growers regularly use, especially on seed beds,
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Florida Agricultural Experiment Station
as much or more ammonia in the fertilizer as is contained in a
ton and a half of cyanamid. As cyanamid is at least as cheap
as other sources of ammonia, the trucker gets the vermicidal
action for nothing. If the dose runs over 1.5 tons per acre, the
excess must be charged to vermicidal advantages. When the
material is applied some time before the crop is planted, much
of the material is doubtless lost.
(2) The best time to apply this.
(3) The best methods of application.
(4) The time that should elapse between treatment and
planting. This will vary with the crop, dose, conditions of tem-
perature and especially of moisture and will have to be worked
out for each truck crop commonly grown in Florida, under the
conditions likely to be encountered. Even the crops that nema-
todes do not seriously attack will have to be tested, for if they
are found to be tolerant of large doses of cyanamid they can
be used as a quick crop to occupy the ground between the time
of application of the cyanamid and the planting of some highly
intolerant plants, such as tomatoes or cucumbers.
As we have seen, the burning effect of cyanamid is much
more pronounced if the soil is dry.
GREENHOUSE EXPERIMENTS
A bench in the greenhouse was filled to a depth of five inches
with infested soil and then divided into seven compartments of
approximately a square yard each. In this bench it was possible
to control conditions better than in the field and especially to
eliminate the migration of nematodes into the treated soil.
Section 1 was treated with cyanamid on March 29 at the
rate of 4 tons per acre. The material was mixed with dry soil
and then wet down. Unfortunately at this time, the importance
of a thoro mixing was not so well appreciated as it is now and
the mixing was not so thoro as it should have been.
Section 2 was treated with cyanamid at the rate of 21/2 tons
per acre. This was dissolved in water but the wet soil was
stirred thoroly.
Section 3 was treated with the same dose as section 2 in
water, but the soil was not stirred; the water was depended
upon to carry the cyanamid down.
Section 4 was not treated, being left as a check. It was
thoroly wet down.
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Annual Report, 1916
Section 5 was treated with cyanamid at the rate 'of 2 tons
per acre, applied as in section 2.
Section 6 was treated at the rate of 1440 pounds per acre,
stirred in dry and then wet down.
Section 7 received the same dose as section 6 but it was added
in solution.
On April 8, these plots were planted to tomatoes, cabbages,
peppers, and lettuce. On the three plots that received the
heaviest doses, a very few vegetable seedlings appeared. On the
three receiving the weaker doses they appeared but soon died.
Section 1 was almost sterile on May 21, there being even very
few weeds. On the check, section 4, there was a vigorous ger-
mination of both weed and tomato seed, the latter were heavily
infested with nematodes and soon died.
The bench was neglected during the summer, not even being
watered except by rain which leaked thru the roof.
On September 11, the bench was again planted to lettuce,
cabbage, celery, carrots, cucumbers, and tomatoes. To our sur-
prise some of these plants on sections 1, 2, and 3 also died.
Evidently, the fact that the plots were dry during the summer
prevented the decomposition of the cyanamid. A few cabbages
in one plot only, section 1, lived. Replantings in this section
showed scorching of the tomatoes as late as January 1916.
These recovered, however, and made good growth. Up to the
present time all plants grown in this section have been free
from nematodes excepting those grown in the small portion
where the September planting of cabbages was not killed. Ap-
parently, in the insufficient mixing, this portion failed to receive
its share of cyanamid.
Section 2 has remained entirely free from nematodes. Evi-
dently a dose of 21/2 tons per acre on shallow soil will kill all
nematodes. Of the seeds planted in November, celery was not
burned at all, cabbage showed some burning, lettuce consider-
able, cucumbers and tomatoes burned badly.
On section 3 the effects were about the same as far as burning
was concerned, but there were a few nematodes on these plants.
This coincides with other experiments which indicate that one
does not get as good results when the cyanamid is added in
water. The top layer of the soil seems to absorb the material.
Section 5 showed one corner next to the check to be heavily
infested, the remainder free. This distribution led to the sus-
picion that the partition between the sections may have worked
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Florida Agricultural Experiment Station
loose; a suspicion which was verified by examination. We be-
lieve the nematodes were exterminated in this section by a dose
of 2 tons per acre.
By May, 1916, there were a few knots noticeable on tomatoes
in section 6. Up to this time none have been noticed. Probably
1440 pounds per acre is a little too small a dose to do thoro
work of eradication, altho it greatly reduced the numbers of the
nematodes.
Section 7, with the same dosage as section 6, but added in
solution, had some root-knot, tho markedly less than the check.
In section 4, check, all plants were so heavily infested with
nematodes that they made very little growth.
In November, a new series of thirteen one-hundredth acre
plots were treated, using from 420 to 3600 pounds per acre. On
three of these plots the material was added in solution. Two
were left untreated for checks. On the other nine about half
of the material was applied as a top dressing and plowed under,
the other half then was added and mixed with the soil by means
of a disk harrow. On all these plots which received 1500 pounds
or less per acre nematodes are now found. On the plots which
received one and two tons respectively, none have yet been
found on the winter crop of lettuce, beans, radishes, etc. The
spring crop has not been dug up.
TABLE 18
TIME IN WEEKS BETWEEN TREATMENT OF SOIL AND PLANTING OF SEED
Quantity cyanamid applied, pounds per acre
4000
R dishes -...........-.......---.. ........--
Turnips .....-.....................
Cabbage and collards.... -to 4
Celery ........... ....... ......... -to 4
Roselle ................ .............
Rape .......... ................ ......... .
Lettuce ...-- ................... .. ..........
Pepper .............................. I
Peas --.. ..........-... 8 to 12
Watermelons ............. to 28
Cantaloupes ............... .......
Cowpeas ...................... 3 to 24
Beans .........--................. i
Irish potatoes ......... to 12
Tom atoes .................... ..........
Cucumbers ......... .. ..........
3000 2000
- to 2 ...........-
-to 8
-to 8 8to 8
I-... to 5
...........-4- t --- --
3 to-- to 8*
...- to 2
-to12 -to12
------------ to 2
4to 14 to 6
......... 20 to 24
1500
-to 11
-to 2
-to 1i
1* to 2
Ito 8
4to 6
3to 7
- to 12
------------
1000 800
-- -to 1
........... -to 1
....... Ito 1
-to 1 -to 1
Ito 2 Ito 2
-to 6 Ito 1
1 to .......
Ito 4 1 Ito 2
3to 6 3*to 4
I to-- I-to-
8 to .
*Trace of burning.
From these plots and other sources we have gathered the
data in table 18 which shows the relative tolerance of plants for
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Annual Report, 1916
cyanamid, and the time which should elapse between the appli-
cation of the material and the planting of the crop for several
different doses. This data is provisional.
In table 18 the first number under each dose denotes the
maximum number of weeks between the treatment of the soil
and of planting, when serious burning occurred. The second
number denotes the minimum time between treatment and
planting, when no serious burning occurred. In other words,
the earliest safe time to plant the crop named opposite the num-
bers lies somewhere between them. The second number repre-
sents the shortest time we have observed to be safe. Doubtless
further experiments will cut this down in most cases.
EXPERIMENTS AT FORT PIERCE
The foregoing experiments were conducted at Gainesville and
apply only to the type of soil used there. On our advice and
under our direction, the County Demonstration Agent for St.
Lucie County, Mr. McLendon, undertook some experiments at
Fort Pierce.
The entomologist visited these plots in June, 1916. They
have developed the following important points:
1. Cyanamid can be applied to pineapples in the field in
doses as heavy as 1500 pounds without injuring them. The
nematodes on pineapples were not exterminated but there seem-
ed to be fewer than on the untreated plants. The pineapples
had a much better color but this was mostly due to the fertiliz-
ing value of the cyanamid.
2. Apparently, on the very sandy soils of the pineapple
fields, a much smaller dose is effective than at Gainesville, and
3. The material leaches out much more rapidly.
Some of the very light pineapple soil was treated with cyan-
amid at the rate of 1500 pounds per acre and a few tomatoes
were set out at once. Altho there was severe burning at first,
the plants recovered and made good growth and were nearly
free from nematodes. On Gainesville soils the tomatoes died
when set out on land with that large an application, even after
a lapse of several weeks. Furthermore, a dose at least twice
as large would have been necessary to exterminate the nema-
todes as thoroly. Evidently the character of the soil will great-
ly modify the procedure outlined here for Gainesville soils.
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Florida Agricultural Experiment Station
INSECTS OF THE YEAR
The most unusual insect outbreak of the year was that of
Diabrotica vittata. Altho we have occasionally received the
striped Cucumber-beetle from West Florida, and the Station
collection contains a specimen from Gainesville, we had never
until this year received a complaint from South Florida, nor is
the insect even mentioned in the Station literature. The first
complaint came from Denaud, Lee County, on October 18 and
complaints continued to come in until the last of April. They
came from as far north and west as Madison, but the majority
were from the east coast-St. Lucie and adjoining counties.
The insects were not observed about Gainesville. In the North-
ern States this insect usually confines its attacks to young cur-
cubits but according to our correspondents they destroyed fields
in which plants were three or more feet long. They killed bear-
ing okra plants as well as watermelons, and even attacked Irish
potatoes.
The most interesting host was citrus, on which they destroyed
the young growth. This is the first record of any Diabrotica
attacking citrus in Florida, altho our common D. 12-punctata is
often abundant in corn fields, especially in the western part of
the State. It is interesting to note that another species of this
genus is a minor pest of citrus in California.
Aleurothrixus howardi, the Woolly Whitefly, continues to ex-
tend slowly into the regions immediately adjacent to its previous
range. We have received it from Palmdale in the extreme
southeastern part of DeSoto County. It is probable that all
citrus communities in that county are infested and the same
may be true of Pasco County. The most serious outbreak oc-
curred in Brevard County, about Melbourne, Cocoa and the
southern end of Merritt's Island. Specimens received from
Georgiana on April 21, consisted of eggs and adults as well as
pupae, and others from Melbourne, on May 4, were mostly in
the first and second larval stages. This is nearly a month
earlier than the time heretofore recorded for the appearance of
the spring brood (see Bulletin 126, p. 90).
The Cowpea Pod-weevil (Chalcodermus aeneus) appeared
more commonly than usual during the spring of 1916. It seems
to be especially attracted to the California black-eyed variety
of cowpeas. In a field near Gainesville where that variety was
growing beside the clay variety, there was less than a tenth as
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Annual Report, 1916
65R
many larvae in the latter as in the former. It was common on
radishes at Gainesville in May.
The June-bug (Anomala marginata) likewise seemed to be
especially abundant during June, 1916. It was received from
Levy to Escambia counties and reported as doing serious dam-
age to a great variety of trees and grapes.
The Twig-Girdler (Oncideres cingulatus) was the cause of
several complaints from the lower East Coast where it was at-
tacking "Australian pines." The curious thing about this
attack on an introduced plant by a native insect was that prac-
tically no eggs were laid in the girdled twigs. Only one egg
was found in the dozens of girdled twigs examined. Evidently
the plant stimulates the girdling instincts of the females but
not the egg-laying instincts.
Respectfully,
J. R. WATSON,
Entomologist.
Florida Agricultural Experiment Station
REPORT OF THE PLANT PATHOLOGIST
P. H. Rolfs, Director.
SIR: I submit the following report of the Plant Pathologist
for the year ending June 30, 1916.
GUMMOSIS
This has been the major problem for the year and the same
plan of investigation was followed that has been reported in
previous years.
Gummosis has shown considerable activity within the last
few months. Reports from different localities indicate a re-
appearance of the trouble in groves where it had formerly been
treated and where it was considered well under control. The
disease shows a tendency to heal apparently or remain dormant
or quiescent for varying periods and again break out in active
form. The conditions predisposing such outbreaks or periods
of dormancy have not been traced as yet to any one factor or
set of factors.
In a former report (Fla. Agr. Expt. Sta. Rpt., 1914, p. lxi.)
some notes were published on a number of diseased areas that
had been kept under observation for a period of thirteen months.
These same areas have been kept under observation now for a
period of more than three years and the data obtained is con-
-sistent with that of the former report.
Eighteen areas were selected representing as nearly as pos-
sible the different stages in the development of the disease. Ten
were active at the time of selection and eight were chosen that
had apparently healed. Notes were taken on the condition of
these areas two or three times during each year thruout the
period. In table 19, the condition of each area is given as it
appeared for that year. All areas were considered active that
showed any recent killing of tissues with gum flow. Where new
tissues were forming and there was little or no gum flow, the
area was considered healing. Healed areas represent those in
which all gum flow had ceased and where the dead surface
bark had scaled off leaving a clean scar.
Seven of the active areas noted in the beginning have appar-
ently healed and remained so the last two years. One has re-
mained active during the entire period and two apparently
healed for a time and became active again. Of the eight areas
that were considered healed at the beginning, two have re-
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Annual Report, 1916
mained so thruout the period. Five have shown an active
period for a time and then apparently healed again. One has
become active and remained so the last two years.
TABLE 19
CONDITION OF GuMMOSIS AREAS UNDER OBSERVATION
Area 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1913....A A H H A A H A A H A A H H A A H H
1914....A H A H A H H A A A H A H A A A A A
1915....H H H H H H H H G H A H A H A H H H
1916....H H H H H H H H H H A H A H A A H H
A, active. H, healed. G, healing.
INOCULATIONS
In the last season several series of inoculations have been
made into large bearing citrus trees. Diseased bits of tissue
from active Gummosis areas have been used as the inoculum.
So far, sufficient time has not elapsed to make a definite report
on them.
A study is being made of the fungus and bacterial flora asso-
ciated with Gummosis areas to determine what relation they
bear to the disease. Cultures have been taken in the field from
different types of areas on different citrus hosts and some of the
organisms isolated are now under study. Phomopsis citri and
Diplodia natalensis have been isolated from Gummosis areas re-
peatedly but when these fungi are introduced into healthy citrus
bark they have failed thus far to produce the characteristic
areas typical of Gummosis.
CONTROL EXPERIMENTS
Experiments at Weirsdale, Fla., for the control of Gummosis
by means of antiseptics have been continued and the results
from the second season's work have not shown so promising.
These experiments will be continued thru the present season
and a full report of the results will be, given in a future report.
MELANOSE
The pruning experiment for the control of Melanose that was
begun in 1913 was continued last season with some modification
in the. original plan. This experiment is being conducted in
a grapefruit grove and the last three years the fruit has not
been picked from this grove until late in the season. This has
interfered with making some of the prunings at the time plan-
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Florida Agricultural Experiment Station
ned, so it was decided this season to change the experiment to
avoid this interference. As the experiment was first outlined
(Fla. Agr. Exp. Sta. Rep., 1913. p. lxxxv) 'a winter and sum-
mer pruning and a combination of the two were provided for.
There are four blocks of trees and block 1 has been left un-
pruned as a check. Block 2 was to be pruned in January and
June. Block 3 to be pruned in January, and block 4 in June.
The first pruning, made in 1913, followed this schedule. In
1914 the January pruning was delayed until the first part of
April on account of the late date on which the fruit was picked.
The trees pruned at this date did not seem to do so well as the
other trees in the experiment and they seemed to suffer more
from attacks of withertip later in the season.
In 1915, the fruit was not picked until the last of April and
the January pruning was omitted for that year. The same
occurred in 1916 when it was decided to change, and make all
prunings in June. The summer pruning has given very good
results in reducing the amount of injury from attacks of Mel-
anose and has not resulted in any perceptible injury or shock
to the trees.
The summer pruning is probably more convenient for the
grower since it can be done at a time when other duties of the
farm are not so pressing and when labor is cheaper and more
readily available. Since the tendency at present is to hold the
grapefruit crop over for the late spring market, it is advisable
to make prunings in such groves during the summer season.
In table 20 are given the percentages of the different grades of
fruit from each block of the 1915 crop. The percentages of
the different grades of the 1913 and 1914 crops are also given
for comparison.
TABLE 20
RECORD OF 1913 CROP
Block No. of When Percentage of
trees Pruned Brights Seconds Russets
No. 1 12 Check 23 74 3
No. 2 16 Jan. & June 47 52 1
No. 3 10 Jan. 40 57 3
No. 3* 6 Jan. 56 43 1
No. 4 12 June 34 62 4
t}
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Annual Report, 1916
RECORD OF 1914 CROP
Percentage of
Block No. of When Perc e
trees Pruned Brights Seconds Russets
No. 1 12 Check 12 73 15
No. 2 16 Jan. & June 35 60 5
No. 3 8 Jan. 34 63 3
No. 3* 8 Jan. 56 41 3
No. 4 12 June 45 53 2
RECORD OF 1915 CROP
Percentage of
Block No. of When Percen
trees Pruned Brights Seconds Russets
No. 1 12 Check 0 62 38
No. 2 16 ........................ 2 73 25
No. 3 8 .......................... 4 68 28
No. 3* 8 ................... 4 68 28
No. 4 12 June 31 52 17
*Carefully pruned by the writer.
It must be remembered that the pruning of blocks 2, 3 and
3* was omitted for the last season, which accounts for the
poor showing made by them in the 1915 record. Melanose was
unusually abundant in this grove during the summer of 1915,
and a great'part of the injury occurred late in the season. This
has been the most severe attack experienced since the pruning
experiment has been in operation.
CITRUS CANKER
Investigation of this disease the past year has been confined
chiefly to laboratory studies of the organism. Special attention
has been given to the growth and behavior of Pseudomonas citri
Hasse in soil cultures, and attempts have been made to recover
the organism from the field soil that has been collected from
under citrus trees that were infected with Citrus Canker.
Bulletin 128, Citrus Canker III, was published in November,
1915, and in this the latest information and facts concerning
the disease were summarized.
Doubtful specimens of Citrus Canker have been submitted to
the Department from time to time for accurate determination,
and many tests have been made to establish the presence or
absence of Ps. citri in such specimens.
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Florida Agricultural Experiment Station
SOIL CULTURES
Ps. citri has been cultured continuously in sterilized soil for
a period of more than a year and the organism has maintained
its vitality and apparently lost none of its virulence during this
period. A marked resistance to desiccation has been exhibited
by the organism. In moist soil a rapid multiplication takes
place and the organisms readily penetrate to a considerable
depth in such soil.
Previous to this experiment the writer did not think that the
canker organism would survive long after being introduced
into the soil. It was considered hardly probable that an organ-
ism of such virulent nature, that confined its attacks to the
aerial part of the host would survive long as a saprophyte in
the soil. The results from the experiment have demonstrated,
however, that the organism grows readily on sterilized soil in
a moist condition and that its virulence is not impaired by con-
tinuous culture on such medium. The bacteria are also capable
of surviving for many months in thoroly air-dried soil, and still
retain their virulent nature, tho their numbers are greatly re-
duced.
A series of soil cultures were made in the spring of 1915,
and have been kept under observation to date. These cultures
were prepared as follows:
Six large test tubes were filled with soil to a depth of four or
five inches. The soil was chiefly sand with a small percent of
clay and humus, and similar to the ordinary upland soil of
Florida. It was thoroly moistened, but not enough water was
added to saturate. The tubes were plugged and sterilized in
the autoclave for thirty minutes at fifteen pounds pressure.
After twenty-four hours each tube was inoculated with one
cubic centimeter of a suspension of Ps. citri from a pure culture
in sterile water. These six tubes were inoculated April 30, 1915,
and numbered from 1 to 6. All tubes were incubated at room
temperature thruout the period which ranged from 110 to 350
C., the average mean ranging from 220 to 250 C.
Tests were made of certain tubes at varying intervals for the
presence of Ps. citri. These tests were made by plating a small
amount of the soil from the tube to be tested in nutrient agar
and noting the colony development in the plates. When tests
were made from moist soil a small amount of the culture equal
to about 0.1 or 0.2 of a gram in weight was removed on the
point of a scapel. This was transferred to a large drop of
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Annual Report, 1916
water in a sterile petri dish. The plate was then poured and
incubated.
Table 21 gives the date, number of different tubes tested and
a statement of the presence of the organism in the amount of
soil tested on that date.
TABLE 21
Date Tubes tested Presence of Ps. citri
May 8, 1915....... Nos. 1, 2, 3, 4 Abundant
May 15, 1915....... -Nos. 1, 2, 3, 4 Abundant
June 3,1915 ....... Nos. 1, 2 3, 4 Numerous
July 10, 1915....... Nos. 1, 2, 3, 4 Numerous
Aug. 24, 1915...... Nos. 1, 2, 3, 4 Numerous in and 3, few in 2 and 4
Sept. 2, 1915...... No. 3 Few in dry soil, numerous in moist
Sept. 30,1915...... Nos. 1, 2, 4 Few in dry soil, numerous in moist
Oct. 19, 1915....... No. 2 Few in dry soil, numerous in moist
Oct. 28,1915....... No. 2 Numerous
Dec. 12, 1915...... Nos. 2, 2a, 4 Few in dry soil, numerous in moist
Apr. 1, 1916...... Nos. 2, 2a, 4 Few in dry soil, numerous in moist
Apr. 8, 1916....... No. 4 Few in dry soil
May 30, 1916....... Nos. 1, 2, 5 Few in dry soil, numerous in moist
During the first tests soil was taken only from the surface
of these tubes and while it was in a moist condition the numbers
of organisms in the small amounts tested were large. As the
soil became dry near the surface the numbers of organisms that
survived were greatly reduced and larger amounts of soil were
used in these tests. About one or two grams of dry soil was
taken for each test and the numbers of organisms obtained
from such samples varied from a few to 100.
The dry top soil in tube No. 1 was poured off into another
tube after the culture had been inoculated for about three
months. Tests were made from the remaining soil as long as it-
remained moist. The last test made of tube No. 1, May 30,
1916, was, however, from the dry soil that had been previously
removed. This soil was thoroly air-dry and could be poured like
sand, and had remained in this air-dried condition for at least
nine months. About five grams of this soil were used for each
test and from 75 to 100 organisms per sample were obtained.
The dry top soil was poured from tube No. 2 six months after
the culture was first inoculated, and numbered 2a. This soil
when tested showed about 75 to 100 organisms per sample.
Sterile water was added to remoisten the soil and later tests
with small amounts (0.1 to 0.2 grams) showed an increase of
many hundred fold in the number of organisms present. The
remaining soil in tube No. 2 was remoistened at intervals and
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a corresponding increase in the number of organisms present
was noted whenever moisture was added.
Tube No. 5 was not opened from the time it was inoculated,
May 30, 1915, until the final test, May 30, 1916. The soil was
thoroly air-dried and would pour like sand. The culture was
well shaken to obtain a composite mixture of top and bottom
soil and tests from this tube also gave living organisms.
Tests of newly-made cultures, ten days after inoculation,
showed that the organisms were rather uniformly distributed
through the soil even at depths of 4 to 6 inches.
Infected soil from the foregoing cultures has been applied
from time to time to healthy citrus foliage and in all cases
canker infections have resulted. Where moist soil from these
cultures has been used a heavy infection was usually obtained.
The air-dry soil gave in most cases only scattering infections.
The soil was applied in most cases to the upper surface of the
leaves and the trees were then thoroly drenched with a fine
spray and kept in a humid atmosphere for at least 48 hours.
The results are given below.
EXPERIMENT I, SEPT. 2, 1915
Seven citrus trees in pots. Young foliage. Dry top soil applied to upper
surface of leaves from tube No. 3. Foliage thoroly sprayed and trees kept
in a humidor 48 hours.
4 Grapefruit seedlings-scattering infection.
2 Rough Lemon seedlings-scattering infection.
1 Budded Grapefruit-scattering infection.
Seven citrus trees in pots. Young foliage. Moist soil from the bottom
of tube No. 3 applied to the upper surface of the leaves. Foliage thoroly
sprayed and trees kept in a humidor 48 hours.
4 Grapefruit seedlings-scattering infection.
2 Rough Lemon seedlings-scattering infection.
1 Budded Grapefruit-numerous infections.
Thirteen citrus trees. Young foliage. Checks. Foliage sprayed and
trees kept in a humidor along with the above.
8 Grapefruit seedlings-no infection.
4 Rough Lemon seedlings-no infection.
1 Budded Grapefruit seedling-no infection.
EXPERIMENT II, JAN. 4, 1916
Potted orange tree, young foliage. Moist soil applied to the upper surface
of the leaves and the tree thoroly sprayed. Kept in a humidor 48 hours.
Soil from culture 2b used. This was a sub-culture made from tube No. 2
by transferring a small amount of infected soil to a tube of sterilized moist
soil. After incubation for several days the culture was used above.
A heavy infection resulted on leaves and stems.
EXPERIMENT III, MAY 8, 1916
Two potted grapefruit trees, young foliage. Soil from tube No. 4 applied
to 48 leave. F6liage sprayed and trees kept moist for several days.
Good infection. Twenty-two leaves infected.
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Annual Report, 1916
EXPERIMENT IV, MAY 31, 1916
Potted orange tree, young foliage. Sprayed, and air-dry soil from culture
No. 5 sprinkled on the upper surfaces of the leaves.
Heavy infection resulted. Twenty-eight infected leaves out of thirty-five:
treated.
TESTS OF FIELD SOIL
Since Ps. citri is capable of growing in sterilized soil, and
surviving for long periods in such soil, under less favorable
conditions for growth, it may be expected to behave in a some-
what similar manner when introduced into field soil under
natural conditions. These organisms may not become so numer-
ous or so generally diffused in field soil as they are found in
cultures, for the environment is very much less favorable and
there are many factors in natural soil that would tend to pre-
vent or hold their development in check. It is believed, however,
that these organisms may find certain more favored spots or
areas in the soil where they become established and survive for
long periods, and that these areas may prove to be centers from
which the organisms are ultimately spread.
Soil under canker infected trees is subject to the introduction
of these bacteria during every period of rain and no doubt
many of the organisms find a favorable habitat in such soil,
and later find their way back to the foliage again thru certain
carriers. Field observations seem to bear this out.
Samples of soil taken from beneath trees that were infected
with Citrus Canker have been tested at different intervals for
the presence of Ps. citri, and while a majority of these tests
have given negative results, in a few cases the presence of the
organism has been established in the sample tested.
It was not found feasible to obtain the organism by dilution
culture methods, and the samples were tested by applying wash-
ings from the same or small amounts of the soil direct to young
healthy citrus foliage. Where canker infection occurred on the
foliage thus treated, the presence of Ps. citri in the sample of
soil tested was definitely established. .The same interpretation
of the negative results would hold true only in a certain meas-
ure, for in most cases small amounts of the samples were used,
owing to the limited facilities for making these tests. An abso-
lute test of these samples would have required the use of the
entire amount of the soil and a larger number of citrus trees
than were available at that time.
The samples were collected by the canker inspectors and sent
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Florida Agricultural Experiment Station
to this Department for testing. Below is given in condensed
form the notes on these samples and the results of such tests.
Sample No. 1. About 1 pounds of soil, collected December, 1915. Soil
taken at one point from 2 to 6 inches below the surface, from an area be-
neath a canker-infected tree that was burned in May, 1915.
Jan. 4, 1916, sample tested. Soil washings from a part of the same; 43
leaves treated, 8 developed canker, a total of 14 spots.
Feb. 1, 1916, sample again tested. Soil washings of entire sample; 147
leaves treated, no infection.
Sample No. 2. About 3 pounds, collected in December, 1915. Soil taken
at a depth of 2 to 6 inches below the surface, from an area beneath a canker-
infected tree that was destroyed in November, 1914.
Jan. 4, 1916, sample tested. Soil washings from a part of sample; no
infection.
Sample No. 3. About 3 pounds of soil collected December, 1915. Soil
taken at depth of 4 to 6 inches below the surface, from an area beneath a
canker-infected tree that was destroyed in July, 1915.
Dec. 12, 1915, sample tested. Washings from a part; no infection.
Jan. 4, 1916, sample again tested. Washings from a part of sample; 32
leaves treated and 4 developed canker infection.
Sample No. 4. About 3 or 4 pounds of soil collected January'5, 1916.
Surface soil at one point for a depth of 2 inches, taken from beneath a living
tree heavily infected with Citrus Canker.
Jan. 11, 1916, sample tested. Soil washings from a part; no infection.
Sample No. 5. About 3 to 4 pounds of soil, collected Jan. 5, 1916. Soil
taken at a depth of 2 to 4 inches below the surface, from under the same
tree as sample No. 4.
January 11, 1916, sample tested. Soil washings from a part; heavy infec-
tion, 27 infected leaves out of 34 treated. Many spots to the leaf.
Sample No. 6. About 3 pounds of soil, collected Jan. 5, 1916. Cross sec-
tion of the soil, 4 to 5 inches in depth. From under the same tree as sam-
ples 4 and 5, at a different point.
Jan. 11, 1916, sample tested. Washings from a part; no infection.
Sample No. 7. About 4 pounds of soil, collected Jan. 14, 1916. Taken at
a depth of not more than 2 inches, from an area where a lime tree heavily
infected with canker had been burned.
Jan. 22, 1916, sample tested. Soil washings of entire sample; no infection.
Sample No. 8. Less than %1 of a pound, collected Dec. 4, 1915. Taken
at a depth of about 6 inches below the surface, from a spot where a canker-
infected tree formerly stood.
March 11, 1916, sample tested. Part of the sample sprinkled on surface
of young citrus foliage; thoroughly sprayed; kept in a humidor 5 to 6 days;
no infection.
Sample No. 9. Less than 1/ of a pound. Collected Dec. 4, 1915. Taken
at a depth of about 6 inches, from an area where a canker-infected tree had
been destroyed.
Mar. 11, 1916, sample tested. Part of the soil sprinkled on the surface of
young citrus foliage, thoroly sprayed and kept in a humidor 5 or 6 days; no
infection.
Sample No. 10. Less than 1% of a pound. Taken at a depth of about 6
inches, from a canker-infected grove where a diseased tree formerly stood.
Mar. 11, 1916, sample tested. Part of the soil sprinkled on young citrus
foliage, thoroly sprayed and kept in a humidor for 5 or 6 days; no infection.
LIGHTNING INJURY
Several cases of injury to young citrus trees from lightning
have come to our attention within the last year. The trouble
has been reported from widely separated areas in the State and
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Annual Report, 1916
while the total loss in most cases has been insignificant, the
citrus growers in the affected localities were very much con-
cerned over what appeared to be a new and serious citrus
disease.
Specimens of the injury were received from different locali-
ties and the reports that accompanied the same seemed to indi-
cate that this was a new disease which appeared suddenly and
spread rapidly from one or more badly infected trees as a
center. Specimens were studied carefully in the laboratory
from time to time but nothing definite regarding the cause of
the trouble resulted from such studies. Attempts were made to
transfer the disease to healthy citrus foliage by contact with
diseased specimens but the results obtained were entirely neg-
ative. Later, a visit was made to the groves in order to study
the disease in the field. Some recent outbreaks were observed
in the vicinity of Lake Alfred, Winter Haven, Haines City and
Lakeland. Six different places where small grove trees had
suffered from injury were visited and the writer was fully
convinced that the injury in each case was primarily caused by
lightning.
Usually one or two trees in each injured lot were more se-
verely affected than the others. Numerous peculiar spots or
blotches were noted on the surfaces of the young green shoots
and occasionally a large branch or limb was observed on which
the leaves were withered. The trunks were not split or lacerat-
ed as is usually the case with other trees when struck by light-
ning. In two instances a narrow strip of dead bark was traced
from the top of the tree down the trunk to the ground but this
was not split or ruptured. At the surface of the ground an
area of dead bark encircled the bases of these trees. On trees
adjacent to the more injured ones, scattering twigs or shoots
were found that were spotted or blotched in a similar manner.
Clusters of three or four shoots of the same age and in the
same condition of growth were frequently observed in which one
or two shoots were spotted or blotched while the others were
entirely free.
Trees, from a few to a dozen or two, may show varying de-
grees of injury when lightning strikes in a grove. Those ad-
jacent to the one receiving the full shock usually show more or
less injury. In some cases, however, it was observed that cer-
tain trees in close proximity to those that were severely injured
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Florida Agricultural Experiment Station
FIG. 10.-Spots on young citrus twigs due to injury by lightning.
Natural size.
were passed over or missed, while other trees beyond showed
injured twigs.
Lightning injury to citrus trees has been previously observed
in the State but apparently no published report was ever made
of it. In a letter to the writer Prof. H. S. Fawcett states that
he observed in Florida some years ago certain injuries on citrus
trees that he concluded were due to lightning and he mentioned
two localities from which the injury was reported. Specimens
of lightning injury were received from these same localities
last season.
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Annual Report, 1916
APPEARANCE
The most striking feature of the injury is the characteristic
spots or blotches produced on the surface of the young green
shoots and twigs. In the first stage of development these are
represented by pale greenish-yellow to yellowish areas outlined
on the surface of the bark, which vary much in size and shape.
In some cases the spots cover only a few square millimeters of
surface and again specimens are observed where the entire sur-
face of the twig is involved for a distance of three or four
inches. The leaf and leaf petiole in such instances seem to
escape injury. Spots
are frequentlyfound
encircling the base
of the petiole and in
specimens where the
entire twig is gir-
dled or invested, the
green leaf petioles
and leaves stand out
in marked contrast
against the discolor-
ed areas.
In later stages the
spots and blotches
became yellowish-
brown and are
raised above the
healthy tissue. The
surfaces are smooth
for a time and are
covered by a thin
glazed membrane
which may become
more or less bleach-
ed with age. The
tissue beneath this
covering is soft and .
somewhat spongy, r-
being composed of
a few layers of dead
FIG. 11.-Lightning injury to young citrus twigs,
cells. In most cases showing green leaf petioles surrounded by dis-
the spots seem to colored areas. Enlarged two times.
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Florida Agricultural Experiment Station
penetrate only a few layers of the surface cells and the cambium
is rarely affected. The growth of the cambium from below
gradually elevates the deadened areas and eventually the sur-
faces of the spots rupture, usually by longitudinal fissures. The
surfaces then become ragged or lacerated and finally slough off
leaving a brownish, roughened scar.
The first stage of the injury noted is probably due directly
to lightning. In this stage the areas are not visibly depressed
but the tissue appears dry and the cells somewhat collapsed.
Tissue thus weakened offers a ready means for the entrance of
fungi and bacteria which may rapidly complete the destruction
of such. A species of Colletotrichum, probably C. gloeosporiodes
is constantly found associated with the spots and blotches and
no doubt this fungus has an important bearing on their later
development.
When a spot or blotch once forms there is apparently no
tendency to increase in size or extend beyond its original limit.
On older branches and limbs which were protected by an
outer corky layer, no spots or blotches were noted and only in
one or two instances were blotches found on leaves that could
have been attributed to the same cause.
LEMON BROWN ROT FUNGUS
Within the past few months a species of fungus which resem-
bles Pythiacystis citrophthora Sm. & Sm. has been isolated from
gumming citrus trees at different points in the State. The
writer first isolated the fungus in March of the present year
at Weirsdale, Fla., from an orange tree that showed typical
symptoms of Foot Rot or Mal di gomma. The same fungus
was later obtained at two other points in the State and it has
since been found in several different localities. So far it has
been isolated only from diseased areas that were -typical of
Foot Rot infections.
Healthy lemons inoculated with the fungus developed a brown
rot similar to that produced by P. citrophthora. The fungus
differs slightly from the latter in certain growth characters but
a sufficient comparative study of the two organisms has not
yet been made to determine definitely whether they are the
same or different species. The fungus is at present under study
to determine what relation it bears to Gummosis and Foot Rot
in Florida.
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Annual Report, 1916
This same fungus was isolated by Prof. H. S. Fawcett in
1914 at Palmetto, Fla., from a grapefruit tree that showed
typical symptoms of Foot Rot or Mal di gomma (Phytopath-
ology Vol. 5, No. 1, p. 66, 1915). The writer obtained a culture
of this isolation at the time but no detailed study was made of
the fungus and the culture was finally lost. A second culture
of this isolation and a culture of a California strain of P. citro-
phthora were recently obtained from Prof. Fawcett. The fun-
gus recently isolated by the writer is apparently identical with
the fungus Fawcett isolated at Palmetto and which he considers
to be Pythiacystis citrophthora.
CITRUS DISEASES
CITRUS SCAB (Cladosporium citri Mass).-This disease has
been quite active the last season, especially on young grapefruit
trees. Attacks on fruit were not so severe as in past seasons.
The fruit of the coming season, especially from the early bloom,
has largely escaped injury this year owing to the dry conditions
that prevailed during the spring months.
WITHERTIP (Colletotrichum gloeosporioides Penz).-Consid-
erable injury from this disease has been reported within the
last few months. This has been especially noticeable in groves
that suffered from the frosts of last March and in groves that
have been poorly cared for.
STEM-END ROT (Phomopsis citri Fawcett).-This disease
was not troublesome last season and was only reported from a
few localities. The dry weather conditions that prevailed dur-
ing the greater part of the picking season was no doubt a factor
in keeping this disease in check.
PECAN DISEASES
The work on pecan Dieback has been along the same lines as
reported last year. Mr. J. Matz has carried out the investiga-
tion and I include herein his report of the work for the past
season together with a report of a new fig disease of which he
has recently made a preliminary study.
Respectfully,
H. E. STEVENS,
Plant Pathologist.
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Florida Agricultural Experiment Station
REPORT OF THE ASSOCIATE PLANT PATHOLOGIST
P. H. Rolfs, Director.
SIR: I submit the following report for the year ending June
.0, 1916.
DISEASES OF VEGETABLES
The work with diseases of vegetables has been conducted this
year as far as practicable along lines followed during the pre-
ceding season, 1914-1915. Chief attention was given to seed bed
diseases, chiefly to "damping off." In connection with these
diseases, some time was given to investigation of seed disin-
fection of several of our most important vegetables. Certain
attention was given to some bacterial diseases not yet quite well
known, such as the black heart" of celery and lettuce. Some
work has been done with an apparently new fungus disease of
tomato fruit which is here being referred to as the buckeye"
tomato fruit rot. The remainder of the writer's time was spent
on a preliminary inquiry into the nature of pineapple wilt, a
new item in the project, and on several minor problems of
vegetable diseases that require immediate attention.
DAMPING OFF IN THE SEED BED
A brief general discussion of the so-called damping off is
given in a previous report (Fla. Agr. Exp. Sta. Rept., 1915,
xcv-xcvli). It is stated there that the Rhizoctonia has been
found to be the most common cause of the disease in Florida.
The study during this year fully supports that statement. Dur-
ing both seasons certain Fusaria that probably were responsible
for a local damping off were found in only a very few instances.
In no instance was Pythium debaryanum Hesse isolated last
year and only in one case was it isolated during the work of
this year-when it was found developing profusely on young
cucumber plants growing in a muck soil in our greenhouse. A
typical damping off was observed in this case. The Pythium
debaryanum at present is being grown in pure cultures in the
laboratory and as it was growing quite profusely on the plants
affected with damping off and around them on the soil, it is-
evident that the fungus can grow readily in Florida.
During this season Rhizoctonia was isolated again from the
same kinds of plants affected with damping off as were used
last year, namely, cabbage, lettuce, celery, cauliflower, eggplant,
:80R
Annual Report, 1916
and tomato. It was also obtained from damping off of castor
bean, cultivated amaranthus, watermelon and cowpea plants;
from a pod rot of garden bean and velvet bean and from a rot
of tomato fruit.
FIG. 12.-Young lettuce plants grown in a wooden flat with soil which pre-
vious to sowing the seed was thoroly infected with Rhizoctonia solani
Kuhn. A, part of flat treated immediately before sowing with 1 percent
solution of copper sulphate at the rate of 500 cc. per square foot of soil
surface; no damping off. B, check; considerable damping off is visible.
Eight strains of Rhizoctonia isolated this season (from lettuce,
castor bean, amaranthus, watermelon, cowpea, garden-bean pod,
velvet-bean pod and tomato fruit) and one received from Dr.
B. M. Duggar of Missouri Botanical Garden were used for inoc-
ulation of seedlings of lettuce, celery, eggplant, pepper and
tomato. The inoculations were made in one series by placing bits
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Florida Agricultural Experiment Station
of pure cultures of the different strains of the Rhizoctonia be-
tween the young plants and in another series by a thoro inocula-
tion of the soil with the same strains of the fungus before sow-
ing the seed. The soil was sterilized previous to the inoculation
and sowing, with 1 to 50 solution of formalin at the rate of one
quart per square foot of the soil. The experiments were carried
on in the greenhouse in wood flats 1 foot square and 3 inches
deep. These flats contained only about 300 cubic inches of
sandy soil soaked thoroly with the formalin solution, of which
not more than one quart was needed. Some additional inocula-
tions were carried out in fresh field soil without previous disin-
fection. The result was the same as with sterilized soil. Some
of the strains of Rhizoctonia were tried also on young plants
of cauliflower, cabbage, cucumber, garden bean, cowpea, water-
melon, beet and castor bean, and.proved able to produce damp-
ing off. The different strains of Rhizoctonia were cultivated
for inoculation purposes and for morphological comparison en-
tirely on bean- and cowpea-pod plugs as this medium has been
found quite satisfactory for the purpose.
The result of the work of last year, 1914-1915, and of this
year leaves, no'doubt, first, that here in Florida, during the. last
two years, Rhizoctonia has been the most common cause of the
damping off of lettuce, celery, eggplant, tomato and several
other cultivated plants; and second, that the different strains of
Rhizoctonia isolated from all these different plants can produce
damping off of every host tried in this work.
From a morphological viewpoint, all the isolated strains of
Rhizoctonia are so much alike that they might properly be con-
sidered as belonging to the same species.
On a previous occasion the writer stated (Fla. Agr. Exp. Sta.
Rept., 1915) that the Rhizoctonia causing damping off of the
plants under consideration is probably the same as the one
affecting potatoes, or is closely related to it. At present it can
be stated that there is enough eviderice for considering it actual-
ly the same organism as R. solani Kuhn; because, first, all of
the strains isolated by the writer are physiologically and mor-
phologically the same as the one received from Dr. B. M. Dug-
gar as R. solani Kuhn; and second, one of my strains, that from
cowpeas developed on young beet plants, a basidiomycete form
answering fully the description of Corticium vagum, B & C var.
solani Burt. These plants were grown in our greenhouse in
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Annual Report, 1916
previously sterilized soil, which was then inoculated with a pure
culture of that strain of Rhizoctonia.
In concluding the statement of the cause of damping off in
Florida, it should be mentioned that in certain instances the
disease is produced by activity of some other fungi'(see Fla.
Agr. Exp. Sta. Rept., 1915, xcvi) such as certain species of
Fusarium, Sclerotia libertiana Fuckel, Sclerotium rolfsii Sacc.
and Phomopsis vaxans (Sacc. and Syd.) Hart. The latter has
been found to attack only the. eggplants, while the former three
are occasionally found attacking almost any of the vegetables
cultviated here. Pythium debaryanum Hesse is mentioned
earlier in this report as occurring here. But all these together
have been by far the less common cause of the disease than the
Rhizoctonia.
CONTROL OF DAMPING OFF
From previous work by other plant pathologists on control of
damping off, it is evident that the disease can be controlled, at
least for a time, by either the steam or formalin methods of soil
sterilization. It is almost impossible to find on a Florida farm-
a steam boiler handy for soil sterilization, therefore, the forma-
lin method, as worked out by J. Johnson (see Johnson, James.
" The Control of Damping Off Disease in Plant Beds." Wis.
Agr. Exp. Sta., Res. Bul. 31; 29-61, 12 Fig., 1914.) which is to
saturate the soil with a 1 to 50 solution of formalin at the rate
of one-half gallon per square foot of the seed-bed area, has been
recommended whenever sterilization was needed. Very com-
monly tho, the seed beds here are not permanent and can be
started each time on new ground, and this has always been
recommended whenever new ground was available. But when
new ground is not available the majority of growers will be
obliged to resort to some method of soil sterilization against
the damping off.
CONTROL BY DISINFECTANTS
The steam and formalin methods are efficient, especially the
former, but they are expensive and somewhat cumbersome. The
writer has been trying during this year some other methods,
hoping to find a more practicable one. On a basis of certain
considerations suggested by the literature on the subject, and
to some extent by personal observation, the following disinfec-
tants were selected for experimentation on control of damping
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Florida Agricultural Experiment Station
off: (1) Sulphuric acid in concentrations of 20, 10 and 5 cc.
of concentrated (1.82 sp. g.) commercial sulphuric acid to one
liter of water, or correspondingly, 2 percent, 1 percent and 0:5
percent solutions; (2) commercial lime sulphur in concentra-
tions of 10, 5, and 2.5 parts of concentrated commercial lime-
sulphur (32 Baume) to 100 parts of water or correspondingly
10 percent, 5 percent, and 2.5 percent solutions; (3) ammonia-
cal solutions of copper carbonate in concentrations of 2, 1, and
1/2 parts of the stock solution (3 pints of concentrated ammonia,
260 Baume, diluted with 5 pints of water, in which then is dis-
solved 5 ounces of copper carbonate) to 100 parts of water, or
correspondingly, 2 percent, 1 percent, and 0.5 percent solutions;
(4) copper sulphate solutions in concentrations of 20, 10, and
5 grams of the salt to 1000 cc. of water, or correspondingly,
2 "percent, 1 percent, and 0.5 percent solutions; (5) calcium
chloride; and (6) sulphur flour in the proportions of 20, 10, and
5 grams to one square foot of the seed bed area. The solutions
were applied to a very moist soil at the rate of 500 cc. per
square foot of the seed bed area.
During the latter part of this year, experiments with all of
these disinfectants were carried out in our greenhouse. For
these experiments wooden flats 12 by 12 by 3 inches were used.
The soil was very light sandy loam, thoroly infected with the
Rhizoctonia three days before the seed were planted. For the
first experiment, lettuce was used because of all the plants
studied by the writer it is most susceptible to damping off.
The soil infected with the Rhizoctonia in one-half of each flat
was then treated with one of the disinfectants while the other
half of each flat was left as a check. (It was watered at the
same time as the disinfection was applied with the same volume
of water as that of the disinfectant, if the disinfectant was in
the form of a solution.) Then all of the flats in the first ex-
periment were sown to lettuce.
The experiment gave the following results:
1. a Sulphuric acid 2%; no germination.
b Sulphuric acid 1%; very poor germination; damping off present.
c Sulphuric acid /2%; poor germination (much poorer than in the
check); damping off present.
2. a Commercial lime-sulphur 10%; germination slightly poorer than in
the check; damping off present.
b Commercial lime-sulphur 5%; germination and damping off about
as in the check.
c Commercial lime sulphur 2/%; same as b.
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Annual Report, 1916
3. a Ammoniacal solution of copper carbonate 2%; no germination.
b Ammoniacal solution of copper carbonate 1%; poor germination;
no damping off.
c Ammoniacal solution of copper carbonate 1/ %; germination poorer
than irn the check; damping off-present.
4. a Copper sulphate 2%; no germination.
b Copper sulphate 1%; poor germination; no damping off.
c Copper sulphate '%%; normal germination; no damping off (see
Fig. 12A).
5. a Calcium chloride 20 gr.; no germination.
'b Calcium chloride 10 gr.; very poor germination.
c Calcium chloride 5 gr.; poor germination.
6.- a Sulphur flour 20 gr.; good germination; damping off present.
b Sulphur flour 10 gr.; good germination; damping off present.
c Sulphur flour, 5 gr.; good germination; damping off present.
All of the checks showed considerable damping off (see Fig.
12B).
Thus, under the conditions of the foregoing experiment, only
the 0.5 percent solution of copper sulphate controlled damping
off and did not injure germination and the rate of growth of
lettuce up to the time when the above data were taken, which
was seven days after the treatment and sowing of lettuce. But,
two days later, the half treated with 0.5 percent solution began
to show some damping off also.
In the next experiment, performed soon after the first one,
the same flats were used with a similar soil inoculated with the
Rhizoctonia. in the same manner. Here the seeds were first
sown and then the soil treated. This time different strengths
of copper sulphate solution were used and besides lettuce other
seeds, tomato, eggplant, pepper, and celery, were tried. Five
flats were sown to lettuce, and four flats to each of the other
four plants. In the case of each kind of plant, one flat was
left as a check, one (or two) treated with 0.5 percent solution,
and two (or one) with 0.3 percent solution of copper sulphate.
In every case 500 cc. of solution was applied to the flat. There
is no need of giving detailed results of this experiment at pres-
ent, for it is sufficient to state that they show: First, that 0.3
percent and 0.5 percent solutions of copper sulphate are not in-
jurious to germination and growth of the five kinds of plants
tried; and second, that the 0.5 percent solution of copper sul-
phate was strong enough either to control entirely or to control
to a great extent the damping off during at least five days after
the time of sowing and treatment. After that time, in most
instances, the disease began to appear. Some additional tests
of a few plants were made in the same flats and at about the
same time. In one case, two applications of 0.3 percent solution
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to the same area were tested. The result was negative and the
damping off was worse than where a single application of 0.5
. percent solution was made.
One percent, 0.5 percent and 0.3 percent solutions- of copper
sulphate were applied directly upon young growing seedlings
of lettuce. The strongest solution in every instance caused
much injury to the plants (scalding effect); the 0.5 percent
solution in one case injured the plants while in another case no
ill effect was observed.
From the work done so far it seems to show that a treatment
of a seed bed just after the seed is sown, with a solution of
copper sulphate of from 0.5 percent to 1 percent strength at the
rate of about 500 cc. per square foot of the seed bed surface (the
soil should be well moistened previous to the treatment) may
prove to be a satisfactory method of at least partly controlling
damping off. Much work is needed before any definite con-
clusion in regard to the best concentration and amount of the
solution and its actual efficiency can be obtained.
SEED DISINFECTION
Because certain seedbed diseases such as the damping off
caused by Phomopsis vexans (Sacc. & Syd.) Hart. can be intro-
duced with the seed, it has been considered necessary in con-
nection with the study of seed bed diseases, to do some work on
disinfection of the seeds of the most important vegetables; such
as celery, lettuce, eggplant, pepper, tomatoes, etc. Very little
work along this line was done by the writer in the previous
year. Many treatments were made this year, using, with but
few exceptions, 1:1000 solution of corrosive sublimate or 1:10
solution of formalin, with the following pronounced results:
Effect of seed disinfection with either of the two disinfec-
tants, especially with the corrosive sublimate solution, depends
largely (beside the kind of seed, concentration of the disin-
fectant and time factors) on the (a) temperature of the dis-
infectant; (b) rinsing of the seed subsequent to treatment; and
in some cases, (c) on the handling of the seed; that is, whether
the seed were sown immediately after the treatment or allowed
to dry up previously to sowing.
At a comparatively cool temperature, 60 to 700 F., all the
tested seed could stand more prolonged treatment than at a
higher temperature, 850 to 900 TF. During the hot weather of
last spring (1916), germination, and the initial rate of growth
Annual Report, 1916
of young lettuce and celery plants were injured to a great
extent even by as short treatment as 10 minutes with 1:1000
solution of corrosive sublimate; the injury to watermelon and
tomato was slight; the same treatment showed no injury or an
insignificant one to eggplant, pepper, cucumber, and cantaloupe.
Drying up of the seed after treatment has been found in
some instances to be injurious, especially in the case of seed
of comparatively rapid germination; such as, lettuce and to-
matoes. And finally, the extent of injury appears to be more or
less decreased by prolongation of the rinsing subsequent to the
treatment.
Formalin solution 1:10 has not been tried during the hot
weather. During the winter time, even a 20-minute treatment
at the room temperature, 600 to 700 F., was not, or very slight-
ly, injurious to most of the seed tried, while 10 minutes was
not injurious to germination of any of the seed tried (celery,
lettuce, eggplant, tomatoes, pepper, cabbage, turnips, onion,
cucumber, watermelon, cantaloupe, and beets).
From the few experiments so far made, it is too early to
make any definite recommendation for disinfection of the seed.
But this much is plain: First, that no seed disinfection experi-
ments can be relied on if the temperature during the treatment
and the subsequent handling is not sufficiently specified and con-
sidered; second, that certain recommendations for seed treat-
ment, e. g., Soak the seed (celery) one-half hour or longer in
warm, but not hot water, then soak one-half hour in corrosive
sublimate 1 part to 1000 of water," may be good under certain
conditions, but may be disastrous when used under conditions
other than those under which the author of the recommendation
worked out his method. The writer finds that at a room tem-
perature of from 820 to 860 F. even 10 minutes treatment of
celery in corrosive sublimate of the strength given, and with
subsequent thoro rinsing of the seed and immediate sowing the
process reduced the germination considerably (over 40 percent
in one instance, as compared with the check) and also retarded
the growth of plants that did germinate. And third, that at a
temperature of 800 to 850 F. all the seed tried, excepting celery
and lettuce, can be safely disinfected in 1:1000 solution of cor-
rosive sublimate for 10 minutes if subsequently rinsed thoroly
in several changes of fresh water or in running water immedi-
ately before sowing.
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BUCKEYE ROT OF TOMATO FRUIT
Buckeye rot, a new disease of the tomato, at least one not
previously mentioned in literature on tomato diseases, has been
under the writer's study since January, 1915. It attacks only
the fruit, on which it appears in the form of a grayish or pale
to dark greenish-
Sbrown, often dis-
FIG. 13.-Buckeye rot of tomato fruit, showing mal shape. The con-
the donated type which gives the appearance sistenctly of the rot
of a buckeye. Three-fifths natural size. 13.)
is aboTheaffeted pame ats
at of the normal fruit, hard when the fruit and some-
bulged or sunken,
but retain their nor-
13wha Buckeyerot of tomato fruit, showing malmature.shape. The con-
The donated type whitacks the fruit only when it touches the ground or
of a buckeye. Three-fifths natural size.
is about the same as
that of the normal fruit, hard when the fruit is green and some-
what soft when mature.
The rot attacks the fruit only when it touches the ground or
is very close to it. Because the fruit naturally has its blossom-
end pointed toward the ground, the rot attacks it at this end,
and for that reason, often appears as a peculiar form of the
blossom-end, rot, for which it has sometimes been mistaken.
The disease is known among some tomato growers of the East
Coast as "water-logged" fruit. The name is misleading and
should not be used in connection with this disease. Some of
the tomato buyers use the name buckeye for a rot of tomato
fruit. Unfortunately the writer had no opportunity to learn
directly just what is being called by this name. His indirect
information leads him to believe that it is used for the rot under
consideration here. As the name does describe very well a most
striking appearance of the rot, that is, the frequently broad
zonation of it, and as the name has never been used in reference
to any other disease related to this, it is suggested here that the
common name "buckeye" should be used in referring to the
tomato fruit rot described here.
The buckeye rot was found first by the writer near Goulds,
Fla., in January, 1915. Later in the same year the rot was
found in practically every tomato field of the so-called "prairies"
of that district (south of Miami) known as Redlands. In the
early spring of 1916 the writer found the same rot on the
West Coast near Bradentown and Palmetto.
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Annual Report, 1916
Two specimens of tomato fruit affected with a rot and pre-
served in formalin for several years in our laboratory, showed
on examination the presence of buckeye rot. One of the speci-
mens came from Little River, Fla., 1911, and the other speci-
men had no label. This information shows that the disease is
not a new one in Florida, and that it is of general occurrence
on low land in South Florida.
This disease has not been described before, tho a somewhat
similar disease of tomatoes was briefly reported from England.*
It is also distinctly different from the rot of tomato fruit pro-
duced by the fungus (Phytophthora infestans) of the late
blight of tomato and Irish potato.
The buckeye rot was observed by the writer to affect as much
as 15 percent of the fruit in the field and 10 percent in transit
and, tho the data as to the actual amount of damage caused by
this disease in the State are as yet not available, it would be
safe to say that it is of importance to the tomato industry.
Isolations of the causal organism, cultural work with it, and
artificial inoculations carried out by the writer show definitely
that the disease is caused by certain fungus of genus Phytoph-
thora. The fungus seems as yet undescribed and should there-
fore be considered a new species.
No direct experiments on control of the disease have been
conducted. But because the rot attacks only the fruit which
is close to or touches the ground, it seems reasonable to believe
that staking the tomato plants will prevent the rot. As the rot
affects the fruit in the field and spreads comparatively rapidly,
it is also reasonable to believe that holding the picked fruit for
a few days before packing it for shipment would enable packers
to detect and discard all infected fruit, and guard against dam-
age caused by the rot in transit.
A more detailed account of the study on buckeye rot is to
be published in a special paper.
SOME BACTERIAL DISEASES OF VEGETABLES
BLACK HEART OF' CELERY
This disease occurs more or less regularly each season and in
practically every place where celery is grown on a commercial
scale in Florida. The color of the rot is from a water-soaked
*Bancroft, C. K. The Brown Rot of Tomato. Jour. Ed. Agr. (London)
16, No. 13,.1013, 1910.
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Florida Agricultural Experiment Station
and greenish-brown to blackish-brown. The number of plants
affected with the disease in some fields this season, 1915-1916,
was running up to 80 percent of the total number of plants, and
the disease is considered by some growers as second to no other
disease of celery in point of the damage it may do and its dif-
ficult control. Some celery growers believe that the disease
depends very much, if not entirely, on the health of the host
plant; too dry or too wet soil, or too much nitrogen in it, etc.,
is believed to result in a severe attack by the black heart.
Microscopic examinations and a certain amount of cultural
work done with the affected plants lead to the belief that the
trouble is due to certain bacteria, tho the writer has not yet
found positive proof that this is true. Whether this disease is
identical to some bacterial diseases of celery reported from va-
rious places, the writer cannot say now.
BLACK HEART OF LETTUCE
This disease is due to certain bacteria and was reported by
this Station on several previous occasions. (See Fla. Agr. Exp.
Sta. Rept. 1908, lxxxvii, xcviii, pls. 4 & 5; 1912, xcviii-c; and
1913, lxxxvii and lxxxviii.) The disease did considerable dam-
age this season in some sections of Florida. On several occa-
sions bacteria identical with those described by H. S. Fawcett
(Fla. Agr. Exp. Sta. Rept., 1908, lxxxiii) were isolated by the
writer this season, but on account of other urgent work the
organism was not sufficiently studied to obtain any additional
information in this regard.
OTHER DISEASES OF VEGETABLES
BLACK SPOT AND BROWN SPOT OF TOMATO
Black spot and rot, or rust ", Phoma destructive Plowr.,
and brown spot or rust", or nailheadd rust", Alternaria
solani (E & M) Jones & Grout.-The black spot disease was
generally prominent in Florida tomato fields during the period
from August, 1914, until near the end of April, 1915 (See Fla.
Agr. Exp. Sta. Rept., 1915, xcviii), while the brown spot dis-
ease was inconspicuous. According to reports the latter disease
was the only one in evidence in May, 1915. It was commonly
observed by the writer during the entire tomato growing season
of 1916, when almost no black spot was found, tho the brown
spot was quite conspicuous and caused considerable loss to the
growers of early tomatoes on the West and East Coasts. The
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Annual Report, 1916
attack of the brown spot this year was confined chiefly to the
central and lower stems and to the lower and usually shaded
fruits. The striking difference in prevalence of one or the other
of the two diseases during the different seasons or different
parts of the same season can be ascribed only to one of two
factors, either to the difference in the temperature or to the
difference in humidity.
The writer had observed abundant black (Phoma) spot of
tomato on the Station grounds early in September, 1914, when
the temperature was above 800 F. The same disease was found
to be common in Redlands (South Florida on the East Coast)
in January, when the temperature was never higher than 700
F. and sometimes down to 350 F. Very little of the brown
(Alternaria) spot was found at the same season. Both seasons
were wet. The brown spot was very common in May, 1915,
and during the entire season of commercial tomato growing in
1916, that is, from January to June; the only factor that was
the same during the two seasons was comparatively dry weather.
The foregoing observations lead me to conclude that the black
spot and rot is a more conspicuous disease during more or less
rainy weather, while the brown spot prevails during compara-
tively dry weather. The temperature within limits common for
Florida seems to have very little or no relation to the preval-
ence of either of the two diseases.
Considering the mode of spore production and dissemination
in these two organisms, one might have reached the same con-
clusion as to the effect of wet and dry weather on the extent of
each of the two diseases, without having made the foregoing ob-
servations.
SOFT ROT OF PEPPER FRUIT
The first specimens of this rot came to the writer's observa-
tion early in July, 1915. On several occasions it was found to
cause considerable damage to the fruit in the field. Isolations
from the rotted fruit invariably gave only one organism, a white
bacteria. By a number of inoculations made with pure cultures
of the bacteria, by repeated re-isolations and re-infections, it
was well established that the bacteria is the cause of the pepper
rot, and that it can produce it only when the epidermis of the
fruit is broken in some way. Inoculations of pure culture of
the bacteria into tomato fruit, carrot and turnip roots, and
potato tubers, resulted in the production of a soft rot much like
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Florida Agricultural Experiment Station
that caused by Bacillus caratavorus Jones. While but little
cultural work has been done with the bacteria, it appears al-
most certain that it is identical with the latter organism.
BACTERIAL BLIGHT OF TOMATO AND POTATO
Bacterial blight of tomato and potato, Bacillus solanacearum
Erw. Sm., was much in evidence this year practically all over
the State and in places caused a great damage to the crops. A
proper crop rotation, field sanitation and control of the sucking
insects were recommended as precautions against the disease.
POWDERY MILDEW
Powdery mildew of garden beans, sweet peas and cowpeas,
has been very common and often destructive to these crops.
The effect of the mildew on the string-bean pod is rather pe-
culiar and on account of its appearance the disease is known
among growers in certain sections of the State as bean rust."
Dusting with sulphur flour or flowers of sulphur has been rec-
ommended against the powdery mildew.
WHITE MOLD BLIGHT
White mold blight of garden beans and English peas, Sclero-
tia libertiana Fckl., was destructive this year in some parts of
South Florida. The fungus attacks all parts of the plants even
those well above the ground. Field sanitation, with destruction
of the affected plants and disinfection of the soil in and about
the affected spots, was recommended to prevent a spread of the
disease.
EGGPLANT FOOT ROT
Foot rot of eggplant, Phomopsis vexans (Sacc. & Syd.) Hart.,
was a very common and destructive disease in many parts of
the State. The appearance of the disease is illustrated in fig.
14. The rot is usually dry, sometimes appearing in the form
of a mere shrinking of the stem tissues at the infected region,
sometimes in the form of a deep "canker." A number of iso-
lations gave the same fungus, P. vexans, the same organism
which causes fruit rot, leaf spot, and stem blight, of the egg-
plant (See Harter, L. L. Fruit rot, leaf spot, and stem blight
caused by Phomopsis vexans. Jour. Agr. Res. 2:331-338, 5 pl.,
1914). Crop rotation, sterile soil for seed bed and seed disinfec-
tion were recommended as measures against the trouble.
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Annual Report, 1916
FIG. 14.-Foot rot of eggplant due to Phomopsis vexavs (Sacc. &
Lyd.) Hart. Natural size.
PINEAPPLE WILT
This disease, which seems to be working its way from the
south (Miami district) to the north (Fort Pierce district), has
been studied only on the East Coast. That is where the bulk of
the crop is produced in Florida. From a commercial viewpoint
it may be stated that only the Red Spanish variety is grown
there. The work on pineapple wilt was started this year. Ex-
amination of many fields affected with the wilt and inquiry
among the growers about the cause of the trouble did not lead
to any definite idea of the probable cause.
The disease can attack plants very early in life, but is prob-
ably more severe in the third and latter years. Its appearance
can hardly be described because the wilt" in this case does
riot mean the same as in that of some other plants; the pine-
apple plant will remain rigid even when it is wilted." Pine-
apple plants affected with the wilt usually show a browning of
the leaves with a peculiar spotting of darker and paler color all
over their surface; the growth of the affected plants is more or
less retarded or stopped; the root system is reduced or almost
entirely rotted off. As a rule, the disease is much more in
evidence in fields which were planted to pineapples before; new
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Florida Agricultural Experiment Station
fields commonly have no wilt, or only now and then a plant. or
small group of plants is affected. There are instances where
some old fields are not showing much of the wilt while some new
fields show as much as 15 percent or even more of it. Dry
weather seems to increase the
Swilt, while rainy weather may
reduce it considerably.
According to the growers'
opinion the following factors
t iare the most important in devel-
opment of the wilt: Planting
the fields with slips taken from
Sickly plants; exhaustion of the
variety and an attempt at reju-
Sn, venation by the introduction of
plants from some other regions,
S'Cuba for instance; lack of hu-
mus in the soil, and hence, grub-
bing under all of the old vege-
table matter, a practice consid-
ered by some growers as very
beneficial to the plants, while
others consider it rather injuri-
ous; and the mealy bug and red
spider are considered by some as
the forerunners of the wilt.
All these factors except, per-
FIG. 15.-Pineapple trunk rot, evi-
dently due to Thielaviopsis para- haps, the introduction of plants
doxa (d. Seyn.) V H6hn. Three- from other countries, provided
fourths natural size. they are not healthy plants,
might have some effect on the
development of the disease. Therefore, it was thought worth
while to conduct some carefully planned experiments which
would show whether or not any of these factors has any bearing
on the disease. For this purpose the writer suggested the fol-
lowing plan to the local growers willing to cooperate in the work:
1. Six plots planted with slips taken from healthy plants,
seven plots planted with slips from wilted plants. Each plot
should contain at least 50 plants and be as narrow as prac-
ticable.
2. Six plots planted with slips from Cuba alternating with
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Annual Report, 1916
seven plots planted with slips from local fields. The plots
should be as narrow as possible and each contain at least 50
plants.
3. Seven plots with the old pineapple plants grubbed under
the soil before planting new slips, alternating with six plots on
which the old pineapple plants were burned over or taken
away. Each plot should contain five rows with at least 25
plants in each row.
4. Seven plots planted with slips treated* against mealy bug
and red spider, alternating with six plots planted with slips not
treated against the insects.
A number of growers were expected to carry out these ex-
periments but only one, Mr. A. L. Hoofnagle of Fort Pierce did
everything in the best way possible. He followed the sugges-
tions almost to the letter, but experiment No. 2 was omitted
because Cuban slips could not be obtained in sufficient number
at the time the plots were planted (September, 1915).
The results of the experiments on Mr. Hoofnagle's place in-
dicate, according to the reports at hand, that only the plots
planted with slips from healthy plants show a distinctly better
result (June, 1916) over the plots planted with slips from
wilted plants. Other plots do not show any benefit for either
of the other factors tested, which were; grubbing old vegeta-
tion vs. burning, and treating the slips against mealy bug and
red spider vs. no treatment. In the latter case the treated plots
appear to be even poorer than those planted with untreated
slips, but this difference can be explained readily by the fact
that the treatment was rather strong and injured many plants.
Later and more careful laboratory examinations of the roots
of a considerable number of pineapple plants affected with the
wilt which were received from various pineapple sections of
the East Coast, showed in almost every case the presence of and
more or less severe'injury by nematodes. The nematodes in
forms of unbroken fresh cysts and in masses of eggs, could be
found embedded in the root tissues and cortex, but no great
*The treatment suggested was to soak the slips for one hour, or less, in a
solution of 1 part of the stock whale oil soap and paraffin oil solution to
50 gallons of water. The stock solution being made of 1 gal. of whale soap,
2 gals. of paraffin oil 24 to 28" Baume, and 1 gal. of water. It was found
later that one hour soaking killed buds in considerable number on the slips
thus treated; half hour soaking left plants practically uninjured.
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Florida Agricultural Experiment Station
enlargements ("root-knots") were observed,* tho the young
growing points of the roots when invaded by the nematodes
showed a considerable increase in diameter, three to four times
normal. These growing and invaded tips are soon killed and
decay; and from one to many new side roots are produced just
above the killed point. In general, a pineapple root system
when affected with the nematodes will on examination disclose
a decided root pruning. Small punctures or holes can be ob-
served on old roots; these are the places where cysts were de-
veloped and later fell away thru decay of the surrounding tissue.
Some manifestations of the presence and effect of the nematodes
on the roots of pineapples are shown in fig. 16.
The injury by nematodes on many specimens is so evident
in the form of a direct and severe pruning of the roots that
there is very little doubt, even at this stage of the work, that
the nematodes are often responsible for the pineapple wilt. The
nematodes also may be responsible for introduction of certain
other parasitic organisms. It is known that even when the
nematodes are not the cause of certain diseases, they are one
of the chief factors for making the host susceptible to it. Thus,
according to L. P. Byers (letter) even varieties of cotton re-
sistant to wilt are affected with the wilt if the cotton is infected
with the nematodes.
The pineapple was known and reported as a host of the ne-
matodes some time before the writer's observations, but the in-
jury was considered "apparently not great." (See Bessey, E.
A. Root knot and its control, U. S. Dept. Agr. B. P. Ind. Bul.
217:7-82, 3 Fig., 3 pl., 1911.)
A great number of isolations from the roots and trunks of
plants affected with the wilt often yielded no fungus or bac-
terial organism at all. In many cases certain Fusaria (on the
whole at least four different species of the genus were isolated
from the pineapples) and a fungus which the writer has con-
sidered as Trichoderma, were quite often isolated, but neither
of the organisms was associated with wilt constantly enough
to suggest itself as a possible cause of it. A number of other
fungi were isolated from diseased roots of pineapples, but each
of the organisms occurred so seldom that they should not be
considered at all in connection with the cause of the trouble.
*Absence of the "root-knot" or rather inconspicuous development of
it on pineapple roots, gives a probable explanation of why the nematode
injury had been overlooked, or,-when found, considered- unimportant:-.
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Annual Report, 1916
FIc. 16.-A, pineapple roots showing common forms of the effect of nema-
tode infection; y, indicating the more prominent points. About normal
size. B, a photomicrograph of root at point x (fig. 16, A) showing two
leaving nematode cysts exposed after the cortex has been removed.
Certain cases of apparent "wilt" were found to be due to
a decay of the pineapple trunk, evidently caused by the fungus,
Thielaviopsis paradoxa (d. Seyn.) v. Hohn.; at least this fungus
was isolated in pure cultures in each case (two samples, five
plants in all) of the rot studied by the author. The rot is
well illustrated by fig. 15. The wilt in this case is due, of
course, to a more or less complete decay of the root-bearing
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part of the plant and can be readily identified on the affected
plants when pulled out.
The same Thielaviopsis was on several occasions isolated from
a leaf spot of pineapples, a disease which had been reported
from various other pineapple growing countries, but not from
Florida.
Respectfully,
C. D. SHERBAKOFF,
Associate Plant Pathologist.
Annual Report, 1916
REPORT OF THE LABORATORY ASSISTANT IN PLANT
PATHOLOGY
P. H. Rolfs, Director.
SIR: I submit the following report of the Laboratory Assist-
ant in Plant Pathology for the year ending June 30, 1916.
PECAN DIEBACK
In the spring of 1914, plans were made for investigating a
certain pecan disease, to determine its cause and nature, and
to find a practical method for its control. This disease has been
in evidence for some time and has caused considerable injury
to pecan trees by killing the younger and less resistant ones.
In older trees this disease kills back the younger shoots and
later affects the larger limbs which ultimately die. (Fig. 17.)
The results thus far obtained from observations and laboratory
study as well as field experiments are that this disease (Die-
back) of the pecan tree is induced by a fungus, Botryosphaeria
berengeriana De Not., which infects young twigs of the pecan
thruout the growing season, usually killing the distal ends. It
causes older branches of the tree to die thruout the summer,
due to a further advance of the fungus from the twigs infected
FIG. 17.-Pecan dieback; tree seriously affected.
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during former seasons. The fruiting bodies produced on the
older branches are mostly perithecia, while those produced on
the more recently infected twigs are mostly of the imperfect
type, pycnidia, containing macro and microspores.
FIG. 18.-Botryosphaeria berengeriana; section thru
stroma.
Specimens of diseased pecan twigs were sent to Mrs. Flora
W. Patterson for identification of the organism present in them
and she stated in a letter that the fungus agrees sufficiently
with Botryosphaeria berengeriana De Not. to be considered as
that species.
ISOLATION OF MICROORGANISMS
During the spring and summer of 1914, a series of attempts
was made to isolate the organisms which might be present in
various parts of the diseased tree. Numerous petri-dish cul-
tures were made from the inner bark and pith of the diseased
and recently infected portions of affected twigs. These cultures
gave several fungi, two of which were found to be present more
or less constantly. These two forms were transferred to culture
tubes containing sterile bean-pod plugs, also to tubes containing
sterile oak-twig plugs, pecan-twig plugs and orange-twig plugs,
as well as various agar media. One form was soon recognized
as a species of Phomopsis; the other produced at first a grayish,
later an olivaceous gray, and lastly dark or nearly black mycel-
ium with woolly sclerotic bodies but apparently did not pro-
duce any fruiting bodies.
A second series of cultures was made from single ascospores
taken from the perithecia found on diseased pecan limbs. A
small portion of the bark containing several perithecia was
placed in a drop of sterilized water in the bottom of a sterile
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