|
Florida
Growers
and Shippers
League
--w NOV 121914 |
U. p a t of Agriouit,
BULLETIN NO 1.
The Citrus Canker Situation In Florida
Compiled by Lloyd S. T I
SNOV 121914 -
A Summary of the papers read and the discussions given at the Citrus
Seminar, held at Gainesville, Florida,
September 22 to 24, 1914.
ISSUED OCTOBER 24, 1914
INV, '60
THE FLORIDA GROWERS AND SHIPPERS LEAGUE.
The Florida Growers and Shippers League has been estab-
lished for the mutual benefit of its members. It is a body incor-
porated under the laws of the State of Florida, but without capi-
tal stock, and to be run without profit. The charter requires that
there shall be an executive committee of nine, three of whom shall
be elected at each annual meeting of the League, which is held at
the same time and place as the meeting of the State Horticultural
Society.
Any person may become a member of the League by paying
the membership fee of one dollar per year and agreeing to pay
the assessments for the support of the work. These assessments
for the present season are as follows:
Citrus fruits and pineapples, one-sixth of one cent per box
or crate.
Vegetables and all other products, fifty cents per car.
Purposes of the League.
The League was established to handle those matters which
all the growers and shippers have in common. The following are
some of the things that have been handled by the League or which
are now being undertaken by it: Hearings before the Interstate
Commerce Commission, when necessary, railroad service in gen-
eral, laws and regulations affecting the shippers and growers,
obtaining better laws and larger appropriations to insure proper
inspection to keep out of the State new diseases and insect pests
and fighting any new insects or diseases which have gained
entrance to the State.
Traffic Department.
The League maintains a very efficient traffic department.
The primary purpose of this department is to make a careful
study of freight rates on perishable products between .Florida
shipping points and the markets, comparing our rates with those'
(3)
our competitors are paying for a similar service. Complete
tariff files are kept and the traffic manager is ready to furnish all
members at any time freight, refrigeration and express rates on
shipments to or from any points. A claim department has also
been established for the members. A charge to cover the actual
cost of collecting the claims has been agreed upon. Members are
asked to correspond with the Traffic Manager at Orlando, in case
they are interested in this part of the work.
E. C. THOSKINS, LLOYD S. TENNY,
Traffic Manager. Secretary-Manager.
Executive Offices, Orlando, Florida.
Executive Committee:
L. B. SKINNER, Dunedin, President.
DR. J. H. ROSS, Florence Villa, 1st Vice President.
H. C. SHRADER, Jacksonville, 2nd Vice Presidenit.
J. C. CHASE, Jacksonville.
Z. C. CHAMBLISS, Ocala.
J. R. DAVIS, Bartow.
A. F. WYMAN, Bradentown.
H. E. HEITMAN, Ft. Myers.
T. V. MOORE, Miami.
THE CITRUS CANKER SITUATION IN FLORIDA.
Considerable interest has been aroused among the citrus
growers of Florida over the introduction of a new disease into
the State. The matter is of such importance and the need for
quick action so great, that the growers attending the Citrus
Seminar at Gainesville, September 22-24, 1914, passed a resolu-
tion asking the Florida Growers and Shippers League to print a
summary of the papers and discussions covering this subject.
This bulletin is issued in response to this request.
History of the Citrus Canker.
(Dr. E. W. Berger, State Nursery Inspector.)
The first time we really realized that we were up against a
new disease was in July, 1913. Mr. Blackman inspected a nur-
sery at Silver Palm and found abundance of the disease in it.
lie found it July 18, and I went down July 28, and brought some
specimens back to the Experiment Station with me. Suffice it to
say, not knowing anything about the disease, certificates were
withheld from this nursery. Arrangements were also made t
give this nursery some treatment. We used Bordeaux. I recalled
that I had found a similar appearing disease a year before at
Monticello. Specimens had been examined at that time and they
were supposed to be an unusual form of citrus scab. Fortunate-
ly, the owner of the Monticello nursery went into bankruptcy and
when I returned there during September, 1913, to see if I could
find the disease still there, the block of trees was still standing
and I found the disease there in considerable quantity. A report
on the disease was made at this Seminar in, October, 1913, by
myself and Professor Stevens. A further report was also made
at the Farmers' Institute, meeting at Lakeland, in February.
1914, and in Bulletin No. 122, issued in April, 1914.
I have given you now the preliminaries of our first observa
lions and experiences with citrus canker in the State of Florida.
I was informed by the owners of the nursery in Dade County that
the stock came from Texas. The infested block in Monticello
also developed in stock that came from Texas. I have later
found that it developed in the Trifoliata stock that originally
came from Japan.
(Dr. Berger then described the conditions he found in the Gulf
States in March, 1914. The following was his summary:)
Alabama.
At Mobile and Grand Bay, carloads of nursery stock, snt-
suma, pomelo and oranges, were found. This stock had been
brought from Texas, Alabama and Mississippi, to be sold and re-
shipped. Traces of citrus canker were found, especially on
pomelo and satsuma. At Grand Bay, citrus canker was found at
every place visited in the nurseries and in the groves.
Mississippi.
Groves and nurseries at Biloxi and Wiggins were examined
and at the latter place citrus canker was found well established.
The manager of the grove there stated that he had first noticed
the disease in 1911 on seedlings coming from Japan.
Louisiana.
'No extensive search was made in Louisiana for the disease
One budded tree was found infected, this coming from Texas. In
as much as many thousand buds have been set out, however, the
majority of these coming from sections known to have citrus
canker, Louisiana probably does contain many diseased trees.
Texas.
Citrus ennker was found at Port Arthur and Alvin. It hal
since been reported that it was found also in South Texas.
Citrus Canker in Japan.
K. Saibarn, of the Saibara Nurseries, Mobile, Alabama, re-
ported that lie first saw the disease on trees imported from Japan
in 1911, but had never seen' the disease in Japan. W. C. Griffin,
Grand Bay, Alabama, first saw it on citrus trofoliata seedlings
from Japan, in Texas. J. H. Giradeau states that a part of the
trofoliata seedlings used at Monticello, were imported direct from
Japan. Professor B. F. Floyd, of the Florida Experimental Sta-
tion, received specimens of citrus canker from a Japanese Plant
Pathologist at the Kyu-shu Laboratory, Kumainoto, Japan. There
is no doubt that they have the disease in Japan.
Of course, it was evident to all that something should be done
in Florida. The matter was brought to the attention of Mr.
Tenny and he at once became intensely interested in it and his
interest in bringing the subject before his Board of Directors
resulted in our sending Mr. Stirling to the Redlands district.
SThrough Mr. Tenny, the Florida Growers and Shippers League
agreed to raise two thousand dollars to pay the expenses of the
work. This inspection work in DI)ade County was inaugurated on
tIe 19th of May.
In response to a question as to the canker situation at
Monticello, Dr. Berger reported that the entire nursery of 20,000
irees had been burned. Two additional infections, however, have
been reported in West Florida along the Gulf coast, at Galliver
and Sanitf Rosa.
(6)
CITRUS CANKER.
(Professor II. E. Stevens.)
During the Citrus Seminar last year I called your attention
to a new citrus disease that had recently been found in the State.
Since then, we have had considerable more experience with this
disease, and have discovered several things of interest in con-
nection with it. It has been named Citrus Canker, and in March,
of the present year, Bulletin 122, was issued as a preliminary
report, in which the disease was described and reported as a new
citrus trouble.
From the data collected and the experience of the past sea-
son, citrus canker has every indication of being the worst fungus
disease of the grapefruit in the State, especially under the influ-
ence of our climatic conditions. It is a disease with which the
glower should not temporize and every effort should be made to
stamp out infections as soon as they appear and extra precau-
tions should be taken to keep any more of the disease from com-
ing into the State.
Appearance of the Disease.
Citrus canker attacks the leaves, young shoots, branches and
fruit, forming a characteristic spot that is similar in general
appearance on any portion of the tree attacked.
The disease has been found on all varieties of Citrus except.
the Kumquat. The Grapefruit is apparently more severely at-
tacked, the infection occurring on leaves, twigs, branches and
fruits. The trifoliata is probably next on the list of suscepti-
bility and some of the sweet orange varieties next. Infections
have been found on the stems, twigs and leaf petioles of trifoliata.
but not on the leaves; on leaves, twigs and fruit of the navel and
other sweet orange varieties. Scattering infectious have been
found on the leaves and twigs of satsuma, tangerine, lime and
rough lemon.
The distinguishing character of citrus canker as observed in
the field, is the typical spot produced on the fruit and foliage.
As usually seen the infection appears as small light brown spots,
from less than one-sixteen-th to one quarter of an inch in diame-
ter. Generally the spots are round and they may occur singly
or several may run together forming an irregular area. The
spots are raised above the surrounding healthy tissue, and are
composed of a spongy mass of dead cells, covered by a thin white
or grayish membrane, that finally ruptures and turns outward,
forming a lacerated or ragged margin around the spot.
On leaves, infections first appear as small, watery dots, with
raised convexed surfaces, and usually they are a darker green
than the surrounding tissues. Sometimes, however, the surfaces
of the spots are rough as soon as they appear. Spots may appear
on either surface of the leaf but do not penetrate through the
leaf tissue at this stage. They gradually increase in size, change
to a light brown, and become visible on both sides of the leaf. In
the older spots one or both surfaces may be bulged or raised,
and such spots are commonly surrounded by a narrow yellowish
band or zone. In the more advanced stages the surface of the
spot becomes white or a-rayish and finally ruptures, exposing a
light brown spongy central mass. Old spots soon become over-
grown by Saprophytic fungi and may present a pink or black
appearance due to other fungus growths.
On the fruits the spots are very similar to those formed ,on.
the leaves. They are raised and retain their circular outline.
They do not penetrate far into the rind and mav be scattered
over the surface, or several may occur together forming an irregu-
lar mass. Gumming is sometimes associated with the spots
formed on the fruits. The fungus apparently does not form a
rotting of the fruits directly, but opens the way for other fungi
to enter and cause infected fruits to rot.
Spots produced on young twigs are characteristic of those on
the leaves and fruit. On the older twig, they are more promi-
nent and more or less irregular in shape.
These spots are formed in the outer layers of the bark tissue
and do not penetrate to or kill the wood. Spots once formed in
the bark are persistent and are not readily sloughed off, but may
remain for a long period of time and form centers from which
infections may readily spread.
Canker Distinguished From Other Diseases.
Other citrus diseases with which canker may be confused
are Scab, Scaly Bark, and possibly Anthraenose, but it can
readily be distinguished from any of these by noting the follow-
ing points:
Citrus Canker Differs from Scab in the-
typically round spots produced; size of spots; white or gray.
ish surface of spots, and the fact that spots penetrate through
the leaf tissue. Does not distort leaves-no wart-like projee-
tions-occurs on older wood, scab does not.
Citrus Canker Differs from Scaly Bark in the-
size of the spots-much smaller and more circular than
Scaly Bark. Spongy character of spots-Scaly Bark spots
hard and glazed. Common on grapefruit-Scaly Bark is not.
Forms spots on leaves-Scaly Bark does not.
Citrus Canker Differs Materially from Anthraenose in the:
size of spots-much smaller than Anthracnose. Canker
spots are raised-Anthracnose sunken. Spongy character of
spots-Authracnose hard. Occurs on young shoots and
older twigs-Anthracnose does not.
LABORATORY INVESTIGATIONS.
The first specimens of citrus canker that were recognized
to be a new and distinct disease were received from near Miami in
the spring of 1913. The infections were on leaves and young
twigs of grapfruit and the characteristic spots indicated plainly
that the disease was very different from Scab or any other citrus
trouble with which we were familiar. Probably some specimens
of this disease were collected by Dr. Berger in the fall of 1912,
and submitted to the office for examination. These were finally
considered to be an unusual manifestation of Scab and no fur-
Iher attention was given to the matter at that time.
The specimens were collected from nursery stock and the
sender wrote that he had seen this same disease or something
very similar to it on trifoliata stock in Texas. These specimens
were carefully examined, but they were so overrun with different
fungi that it was impossible to tell what was the cause of tino
disease from a mere examination of this material. Investigations
were later begun to determine, if possible, the cause of the trouble.
An examination of all available literature on citrus diseases
failed to show any mention of a disease similar to this on citrus
fruits.
(Then followed an account by Professor Stevens of his
efforts to discover the cause of citrus canker. Experimentz-
showed that the disease was infectious. Pure cultures of a
fungus were isolated and the disease has been obtained artificial-
ly by using this fungus. Extensive laboratory experiments aie
being carried on and in the near future a bulletin will doubtless
be issued by the Experiment Station giving the results of thil
investigationn)
Control.
The problem of controlling citrus canker is going to be a
difficult one. and a greater undertaking than the average grower
can successfully attempt. What I mean by control is to thor-
ounghly eradicate the disease from infected trees and still be able
to save the trees. With the present distribution of the disease,
confined as it is, to the comparatively small area in the State, I
would advise the complete destruction of all infected trees just
as soon as the infection appears, whether such trees are in the
nurseries or groves.
ERADICATION OF CITRUS CANKER.
(Frank Stirling.)
Citrus Canker Conditions in Dade County.
There is hardly a grower of citrus fruits in the State of
Florida, who has not learned of the newest and by far the most
feared disease of citrus, namely-Citrus Canker.
It is a well known fact that Mr. Lloyd S. Tenny, of the Florida
Growers and Shippers League, took up the matter of financing at
campaign against the citrus canker, there being no other funds
available at that time for the work, and made an effort to com-
pletely eradicate the disease in the State.
Along the middle of May, of this year, I was employed by Mr.
Tenny to undertake the work under Dr. Berger's instructions.
and with that end in view came to the southern part of Dade
county, where the canker was at that time beginning to cause
trouble.
It was thought at first that there would not be more than
ten or a dozen properties having any canker in them, and that it
would be a matter of a few weeks only, possibly two months, to
clean up the disease in that part. I found, however, that there
were in all, in Dade county, ninety-five properties having citrus
canker infection, extending from Fort Lauderdale, on the north,
to Detroit, on the south, a district fifty-five miles long and in
width from the ocean to the Everglades. Fully eighty per cent.
of the disease, was, however, in the southern part of this district,
in a section about three and a half miles in diameter, having the
little hamlet of Silver Palm for its center. In this section, the
citrus industry has developed with wonderful rapidity.
The amount of clearing and planting is almost unbelievable.
In Dade county, south of Miami, there are now some eight hun-
dred thousand trees in groves. Almost three hundred thousand
of these trees are in the Redlands district, and it is safe to say
that fully eighty per cent. of the whole is grapefruit.
The Campaign Launched.
When the Florida Growers and Shippers League first took up
the matter of citrus canker eradication in this section, fully 90
per cent. of the growers were ignorant of its presence. They all,
however, soon learned of it, and, wishing to assist in the work
of eradication, organized a sub, or branch of the Florida Grow-
ers and Shipper League, which at the present time has a paid-up
membership of 250.
We knew that this new disease attacked the leaves and lh1
young shoots and the fruit-that when the tree became affected
its growth was stunted, and all the fruit was reduced to culls.
It was learned that it was not like other diseases, amenable to
treatment. Spraying did no good whatever.
At the outset we deemed it necessary that all infected groves
and nursery stock should be cut back, defoliated, and their trunks
painted with Bordeaux or carbolinium. This appeared like a
radical treatment, but there seemed nothing else to do, and we
went at it bravely. We cut back and treated in this manner
over two hundred thousand nursery trees and over five hundred
acres of grove trees. This was in May, June, and the first part of
July.
At this juncture everyone began to breathe a little easier.
People went on clearing land and planting new groves. Several
weeks passed. The inspection and the treatment went on. More
and more infection was found and more and more treatment was
applied. What was at first thought to be a very local infection
proved widespread. Instead of a dozen properties diseased, a
score were found, and then fifty, and then almost a hundred. Still
we kept on fighting--cutting back and treating with Bordeaux and
earbolinium.
Consternation at Spread.
But the worst was yet to follow. The groves cut back and
painted and left for clean began to put out new growth. Imagine
the consternation when it was found that this new growth still
showed the infection-that all of our treatment had been useless.
We found that we had been actually spreading the disease. In
one grove, for instance, there were twelve trees originally treated.
When the new growth appeared there were forty infected. What
was to be done? Positive advise was not to be had-we had no
precedent to follow. In the absence of knowing what else to do
we redoubled our efforts, but the disease, every time it was felled,
arose ten-fold stronger. In a short time we were "up against it"
in two different ways-lack of funds and lack of knowledge.
The growers went into their own pockets as they had never done
before. The growers, the business men, the banks, the Board of
Trade of Miami, professional men-even the women, doing their
share.
So the money was raised, but we still lacked the knowledge
as to what to do. We had followed the only known remedies with-
out success. Washington was appealed to, and a man, we were ad-
vised, was detailed to our assistance. But even he had first to
make a tour through Alabama, Mississippi, Louisiana and Texas,
where the disease is of longer standing, before he could come
to us.
The Fire Treatment.
In the meantime, a number of the growers and others in the.
district began trying out methods that might prove successful and
experimenting with other things. At this juncture, Dr. Hiram
Byrd proposed a method of treatment-of applying a forced flame
to the diseased trees. If cutting the trees back and painting them
was a radical procedure, what was to be said of turning a spray
of burning oil upon the infected tree and practically reducing it
to ashes?
The rationale of the method is this: That the disease is of
a fungus nature; that it spreads by dissemination of spores; that
these spores are washed off the infected trees and get on the
ground, the grass, and rocks beneath the trees; that when the
tree is treated otherwise, the tree itself may be clean, but it has
the infection all around it, from which it becomes re-infected as
soon as the new growth puts out; that in cutting back the trees,
the tools, clothing, hands, etc., of the workmen become infected,
and when other trees are handled, they likewise become infected;
that no method of treatment can succeed that does not take into
account all these factors.
This method of burning the trees is to spray a mixture of
kerosene and crude oil upon the tree, the grass and the soil be-
neath, until the tree is charred. In this way nothing comes in
contact with the disease except the forced flame, and there is
absolutely no danger of carrying the disease to healthy trees.
Spreads Rapidly.
This disease is, without doubt, the most infectious of any
known on citrus trees, and during a time when the atmosphere is
humid, such as in the rainy season, it spreads rapidly. I have
found during the early part of the season that it requires two or
three months for the canker to infect and mature, so as to re-
produce itself, owing, no doubt, to the dryness and coolness of the
weather. Under favorable conditions, however, the canker will
infect and mature in much less time, and it is certainly a good
thing that we began work when we did or we never would have
caught up with it.
As I have said before, this disease is by far the worst that
has ever affected the citrus industry. It is so deadly that when
the tree first becomes infected in this territory it is worthless
inside of two or three months.
What Has Been Accomplished.
For the past two months we have been passing through the
worst of the fight. We have destroyed every tree showing the
slightest infection. We have done this by applying the torch,
which resembles a plumber's blow torch, only a hundred times
larger. The diseased trees were burned to a crisp. The torch
was also applied to the surrounding ground. The cost has ex-
ceeded one hundred dollars per day. (This does not include the
$2,000 which the Florida Growers and Shippers League is spend-
ing). We have burned in the Redlands district alone 1,933 grove
trees and 101,300 nursery trees. Over 200 grove trees and a good
many thousand nursery trees were burned in the Miami district.
We have in the two districts some fifty odd men employed in
the work of canker eradication.
Entire State Threatened.
If we fail to eradicate the disease here, then the entire State
is in jeopardy, as it would be merely a matter of months before
it would be all over the orange belt; and if every grower in the
State of Florida knew of the deadliness of this disease as we do
here, and of the rapidity with which it spreads, not one of them
would rest a moment so long as there was a trace of it left in
Florida. Another thing-if this disease had been permitted to
go on six months longer before taking steps for its eradication. ]
doubt if one hundred thousand dollars would have completely
eradicated it.
Varieties Affected.
We have found the disease upon all the varieties of citrus,
with the exception of the Kumquat, although the grapefruit seemin
to be by far the most susceptible of them all. The order adopted
according to the degree of infection observed is as follows:
Grapefruit, citrus trifoliata, Persian lime, Key lime, naval orange,
sweet orange, Salsuma, tangerine, mandarine, King orange awl
lemon. The seedling and triumph grapefruit seem to be the mo-t
susceptible of the pomelo.
Citrus canker has not yet been observed on any non-eitrus
plants.
Effect on Trees an,' Fruit.
The great danger here in this section, where almost every-
thing is grapefruit, lies in the fact that it is principally a grape-
fruit disease. As was stated in the first place, in articles by Dr.
Berger and others, this disease attacks the twigs and leaves of
these pomelo virulently, resulting in a putting out of more twius,
thus overloading the tree with small branches. It is also virulent
in the manner in which it affects the leaves-spotting' them, caus-
ing' them to turn yellow and to drop prematurely. With the
oranges the disease is not so often seen upon the leaves and
twigs, but upon the fruit itself, causing spotting to a considerable
extent.
In one grove in the vicinity of Silver Palm, there are four
acres of grapefruit trees, about seven years old, bearing from two
to twenty boxes of fruit per tree. During the first week in June
these trees were inspected and found to all appearances free
from citrus canker. Three weeks later one tree began to show a
slight infection upon one of the limbs. Four days later I made a
careful canvass of the grove and found that the disease had
spread to five trees. The owner was away at the time, and when
he returned a week later, the disease had spread to twenty-seven
trees. I could have had no trouble whatever in picking fifty
boxes of diseased fruit that was all covered with the canker,
some of which were beginning to rot and fall off. By the time we
could get the consent of the owner to burn them, three days later,
the disease had spread and we burned over fifty trees.
Fortunately there were not many large bearing groves in the
section-this being a new country-and, consequently, the loss
per tree has not been so great as it would have been had the dis-
ease broken out in an older country. Most of the trees were
under three years old. However, I want to say that this disease
attacks a large bearing tree as rapidly as it does a young tree.
How the Work Is Done.
When we learned that this disease was so terribly infections
we began to take every precaution in regard to disinfecting our-
selves, tools, etc., to prevent carrying the infection from tree to
tree, and from grove to grove. The men on the job are supplied
with suits similar to the harvester's suits used in the West. (We
secured 72 of these suits). The men use them in the groves.
When they leave one grove they take off the suit they have on,
dip it into a solution of Mercury Bi-chloride-strength one to one
thousand-and put on another to use in the next grove. No one
i, ever permitted to touch a tree, whether diseased or not. So
particular and careful have the growers become that anyone
trespassing-innocently or otherwise-is apt to get into serious
trouble.
The growers get together once a week to receive reports on
the progress of the canker eradication work and to discuss ways
and means for carrying on the work, as we deem it necessary
to keep on inspecting for several months after the last canker
has been seen.
Practically, no new infections have recently been found, al-
though there are recurrences of the disease in those groves where
heretofore canker was found; but even this is growing smaller
week by week, and this being the rainy season and the time of the
year when the disease is most apt to spread, conditions are cer-
tainly favorable. The growers are not by any means "out of the
woods" yet, but we have come to the "turning of the road with a
straight way ahead," and we but need the vehicle--finances--
to go on.
Progress Made.
We have already made a tree to tree inspection of everything
in the section and are now on the second inspection. The thor-
ough inspection of nearly a million trees, to take a look at
practically every leaf on those trees, is, as you see, quite an un-
dertaking. We make an inspection of the groves which
have beep found diseased, not less than once a week. This
means that we have to inspect some 45,000 trees every week. We
use for this work about 12 special inspectors who do nothing but
re-inspect. It is in this re-inspection that we now find most all
of the canker, and as I said before, that is becoming less and less.
When we first began this burning campaign the number of trees
infected of those inspected was 15 in every one thousand, or
11-2 per cent. Now, that percentage has fallen to 1-4 of one
per cent. At the present time one tree in every 167 trees in the
entire section has been burned. We believe that by holding down
the disease and gradually decreasing the percentage during the
wet season, that by the time the dry cool season sets in there will
be no trouble to make a complete eradication.
Every precaution for preventing the spread of the canker
has been urged. The State Inspector of Nursery Stock has re-
voked all certificates in the diseased district. This alone has proven
of great value to us. Certain recent developments have proven
that nurseries that three months ago were apparently healthy and
clean have recently developed canker. If the buying and plant-
ing of trees had gone on as before it is hard to tell how much
farther the disease would have spread. Any way, our work would
have been made much harder in locating and eradicating these
new infections.
The success of our work in canker eradication has depended
entirely upon the splendid organization and co-operation of the
growers themselves. In the first place, we had for the president
of the local branch of the Florida Growers and Shippers Leagun
one of the best men obtainable for that office. Mr. W. J. Krome,
construction engineer of the F. E. C. Ry., who is vitally interested
in grove culture in this part of the State. Another thing was that
we had only men who are grove owners and property holders
engaged upon the work of fighting the canker. All of these men
are vitally interested in the welfare of the comnnry and most of
them have given up their own private interest in the meantime to
help fight the common enemy.
Experiments and investigations in regard to the nature of this
disease have been and are being carried on by Prof. Stevens of the
Experiment Station at Gainesville and by Dr. Wolf, of Alabama.
However, a committee has been appointed in the Redlands section
to carry on some experiments in the diamsed territory there.
There we have learned some things that an quite valuable to us
in our work. We know that where we hima burned the trees and
surrounding ground and where the new skoets have sprung 'ip
from the roots, in no case has the infection returned, which shows
conclusively that the roots were not infeetSML However, only a
few of the trees have sent forth sprouts where they were burned
In many cases the trees are entirely dead.
Spread in Warm Weeao.
We know that during the warm, wet periods, the disease in
fects quickly, and matures in a few days. I took a tetf having
two postules of the canker on it, soaked it in water one teinute
drew it through my thumb and forefinger once, then drew a, Loe
that was on a healthy potted grapefruit seedling through ml
thumb and forefinger once, with the result that in eight days on
that leaf I counted over fifty tiny postules of the disease. Ir
four more these postules had developed to maturity-that is
they had burst open and were infecting the other leaves on the
seedling. To learn if the disinfectant-Bi-chloride of Mercury-
which we were using was effective, I repeated the experiment
using a solution one to one thousand, Bi-chloride of Mercury, ir
which to soak the diseased leaf-this with the effect that no in-
fection occurred on the healthy leaf. We have also noted tha'
where groves had been repeatedly sprayed with Bordeaux, even
though they are close to an infected grove, that the chance of their
becoming infected is considerably lessened, although the Bordeaux
does no good after the tree is first infected.
Conclusion.
Now, the question arises: Is it worth while to resort to this
drastic method of eradication-that of burning the diseased tree?
Ti certainly is heartrending to burn beautiful trees which, in some
cases, have ten to twenty boxes of fruit on them. As I have said
before, we have burned in the Redlands district one tree in every
167 trees, or something like one-half of one per cent of the whole
number of trees in the section. We consider that if we could
make an entire eradication by sacerificing ten per cent of the whole
(16)
number of trees in the section. it would be worth while, and I feel
confident that we will not lose more than one per cent of the total.
While there may be found some remedy to effect a control of the
disease, I doubt it very much, and even if there is, our knowl-
edge of other diseases shows us that eradication at almost any cost
is preferable to any methods of control. Take citrus scab for
instance,-I am told by good authorities that this disease will
cause something like a hun dred thousand dollars loss to the citrus
growers of the State thi's year. One tenth of that amount, if
applied properly at the start, would have stamped it out com-
pletely, as could have also been the case with the white fly in 1896.
So with this new, and by far the most terrible disease yet known
infecting the citrus industry in Florda, we deem that the only
way to handle it is by complete and absolute annihilation.
|
