HoRTICU LTURAL ENTONIOLU)GY
Techniques for Monitoring Cranberry Tipworm (Diptera:
Cecidomyiidae) in Rabbiteye and Southern Highbush Blueberries
ERIN M. SARZYNSKI AND OSCAR E. LIBURD
Department of Entomology and Nematology. Building 970, Natural Area Drive, P.O. Box 110620, University of Florida,
Gainesville, FL. 32611
J. Econ. Entomol. 96(6): 1821 1827 (2003)
ABSTRACT Several monitoring techniques were evaluated for their effectiveness, based on the
highest mean captures of cranberry tipworm, Dasineura oxycoccana (Johnson), in detecting D.
oxycoccana in rabbiteye, Vaccinium ashei Reade. and southern highbush, V. corynmbosum L. X .
darrowi Camp, blueberry plantings. There were no ,, .I. 1 i .. ; in captures of D. oxycoccana
adults on unbaited sticky board traps, regardless of color (yellow, white, green, or blue). In a separate
experiment, three monitoring techniques, yellow unbaited sticky boards, larval! adult emergence from
infested buds, and bud dissection, were evaluated for detecting D. oxycoccana, eggs, larvae, and adults.
In total, four bud types were examined, including rabbiteye floral, rabbiteye leaf, southern highbush
..i and southern highbush leaf The emergence monitoring technique detected significantly more
D. oxycoccana adults than the other techniques evaluated. Emergence and dissection techniques
performed -!. I11 II > .- detecting D. oxycoccana larvae. Dissection was the only technique capable
of detecting D. oxycoccana eggs. Overall, the highest numbers of D. oxycoccana eggs were detected
in southern highbush leaf buds. However, larval infestation was lower for southern highbush leaf buds
compared with other bud types sampled. Hypotheses to explain this phenomenon are discussed. The
fewest number of eggs was recorded for southern highbi. i 1 ... I: ... .:..., .11 I ..... these buds
develop before peak emergence of D. oxycoccana. Managing D. oxycoccana in infested plantings can
be improved by incorporating monitoring techniques, specifically bud dissection to search for eggs,
that will aid growers in making timely insecticide applications.
KEY WORDS Dasineura oxycoccana, Vacciniurn spp., traps, monitoring
TtIE CRANBERRY TIPWORM, Dasineura oxycoccana (John-
son), is a recently discovered pest of 1 1 .. V.ac-
cinium ashei Heade, and southern highbush, Vac-
cinium corymbosum L. X V darrowi Camp,
blueberries in the southeastern United States (Lyrene
and Payne 1992). Female flies ... .:: eggs into sus-
ceptible floral and leaf buds, and during heavy infes-
tations, more than one female may oviposit into a
single bud (Bosio et al. 1998). Larvae feed on plant
juices, which ultimately kills developing buds (Mahr
and Kachadoorian 1990). Unmanaged D. oxycoccana
infestations can destroy up to 80% of floral buds in
susceptible rabbiteye cultivars (Lyrene and Payne
1992, .: ).
Until recently, the presence of D. oxycoccana in
Florida blueberry plantings was misdiagnosed as
freeze damage (Lyrene and Payne 1995). This dis-
crepancy has complicated accurate assessment of flo-
ral and vegetative bud loss in blueberry plantings
throughout Florida and much of the southeastern
United States. Lyrene and Payne (1992) were the first
to identify D. oxycoccana affecting floral buds within
rabbiteve blueberries. }i :.! .... have since been
identified in blueberry plantings in Italy and other
European countries (Bosio et al. 1998).
Currently, the Florida blueberry industry is under-
going a conversion from long-established rabbiteye
cultivars to southern highbush cultivars, with acreage
of southern highbush increasing 23% from 1989 to 2000
( i ..1. ... et al. 2000). The trend toward commer-
cial production of southern highbush plantings in
Florida is a response to an increased market for early-
season blueberries, which have a higher market value
than later ripening blueberries from primary blueber-
ry-producing states (Williamson et al. 2000). Despite
this trend, blueberry production in Florida may be-
come limited by an expected increase in insect prob-
lems (Mizell and Johnson 2001). In a recent crop
:.. i. for blueberries in the southeastern United
States, D. oxycoccana was listed as a major pest war-
ranting attention, particularly with regard to monitor-
ing strategies and evaluation of alternative chemical
management protocols (NeSmith 1999).
According to Gagn6 (1989), adult D. oxycoccana live
only long enough to mate and lay eggs, -2 to 3 d.
Cranberry tipworm is known to have overlapping gen-
erations throughout its described range, which in-
0022-0493/03/1821-1827$04.00/0 2003 Entouological Society of America
JOURNAL OF ECONOMIC ENTOMOLOGY
eludes the southeast as well as cranberry- and blue-
berry-producing areas in the north (Liburd and Finn
2002). Mahr and Kachadoorian (1990) reported that
D. oxycoccana completed up to five generations in
Wisconsin cranberry bogs, although later work by
Cockfield and Mahr (1994) suggested that distinct
broods are not easy to distinguish. In Mississippi, D.
oxycoccana are capable of completing up to 11 gener-
ations per year (Sampson et al. 2002).
Reliable techniques to monitor and .-h *..i pop-
ulations of D. oxycoccana in blueberry plantings have
not been thoroughly evaluated. Currently, yellow
sticky boards are used within some plantings to mon-
itor the presence of adult midges and the abundance
of their natural enemies (Bosio et al. 1998; B. J. Samp-
son, USDA, Poplarville, MS, personal comrmunica-
tion). Other colors of sticky boards have not been
evaluated in the United States, despite knowledge that
dipterans can be monitored effectively using various
colored traps (Vernon and Broatch 1996, Liburd et al.
1998). Other frugivorous insects such as i' ;.., : ,i
Frankliniella spp. (Thysanoptera: Thripidae), respond
to blue and white (Cho et al. 1995, Childers and Brecht
1996). Because 1i thrips are another key pest in
Florida blueberry plantings, and because they affect
blueberry production during approximately the same
time interval as D. oxycoccana (unpublished data), the
development of a trapping technique that may simul-
taneously monitor the presence of both pests is de-
sirable.
Our objectives were to determine whether color
i ... captures of D. oxycoccana adults on un-
baited sticky traps in the field and to evaluate several
sampling techniques for detecting various F
D. oxycoccana. Finally, we compared 1.1 .. o and
southern highbush floral and leaf buds for the pres-
ence of D. oxycoccana eggs and larvae.
Materials and Methods
All experiments were conducted in 2-ha blocks of
rabbiteye and southern highbush plantings in north
central Florida. Bushes in the rabbiteye planting were
unmanaged for at least 3 yr before the start of studies
and were 22-3 m in height in 2002 and -1.5-2 m in
height in 2003 (after pruning in July 2002). The plant-
ing was located in Windsor, FL, and consisted of
-. 1 1-. 'Bonita,' and 'Climax'. Bush spacing was
1.5 m apart and 2.4 m between rows. Bushes in the
southern highbush plantings were managed commer-
. :I1 and were 1.5-2 m in height at each of the two
sites. One southern highbush planting was located in
Inverness, FL, and contained 'Misty,' 'Jewel,' and
-i...; .. '. Bush spacing was 1.5 m apart and 2.4 mu
between rows. A second southern highbush planting
was located in Windsor, FL, within 500 m of a rabbit-
eye planting. Bushes in the second southern highbush
planting were multiple clone types (no cultivar iden-
tification) and spaced 1.5 m apart with 1.5 m between
rows (high-density bed).
Unbaited Colored Traps. Experiments to evaluate
the effect of color for monitoring D. oxycoccana adults
by using unbaited sticky traps were conducted in rab-
biteye and southern highbush plantings in Windsor
and Inverness, FL. respectively. In 2002, D. oxycoccana
adults were monitored once per week for a 6-wk
period, from 5 March to 12 April, at the 1..:
planting and from 31 January to 6 March at the south-
ern highbush planting. In 2003, monitoring was con-
ducted only in the rabbiteye planting because data
from the previous year indicated that D. oxycoccana
populations were too low in the southern highbush
planting to waarrnt sampling again. Monitoring was
conducted twice per week from 6 to 21 March (five
sampling dates in total). The monitoring period for
each planting included the seven stages of II .' bud
development as outlined by Spiers (1978).
Various colors of. ....... .. ..: .1 ... .l. .. I .. ctangu-
lar unbaited sticky board traps (treated area 394 cm2;
Great Lakes IPM, Vestaburg, MI) were used to mon-
itor D. oxycoccana adults in commercial blueberry
plantings. Four trap colors were evaluated: 1) standard
Pantone -. II ,2) safety white, 3) walnuthusk green,
and 4) thrips blue. Experimental design was random-
ized complete block with four replicates per treatment
in each planting. Traps were hung within the canopy
., I ... in a vertical position and spaced 10 m apart
and 15 m between blocks. Traps were rerandomized
and replaced once per week in 2002 and twice per
week in 2003. Traps that were removed from the field
were covered with a layer of plastic wrap and trans-
ported back to the laboratory for a two-stage visual
analysis.
In the initial analysis, traps were screened for D.
oxycoccana adults by using a benchtop-illuminated
magnifier (three-dimensional, Cole-Palmer Instru-
ment Co, Vernon Hills, IL). All specimens with mor-
phological characteristics resembling D. oxycoccana
were encircled on the plastic and subjected to a sec-
ond analysis. Positive identification of D. oxycoccana
was conducted using a 10X dissecting microscope.
Raymond Gagn6 (USDA ABS, Beltsville, MD) and
Blair Sampson (USDA-ARS, Poplarville, MS) con-
firmed the identification of specimens. The most ef-
fective trap color was determined based on the highest
mean captures ofD. oxycoccana adults throughout the
season.
Monitoring TI.. h!!|;.. Experiments to evaluate
techniques for detecting various life stages of D. oxy-
coccana were conducted in both rabbiteve and south-
ern highbush plantings in Windsor, FL. Three tech-
niques were evaluated for their effectiveness in
detecting and i.. : .. ,,"-._ D. oxycoccana: 1) use of
unbaited yellow sticky boards, 2) collection of bud
samples for larval/adult emergence, and 3) II i-
. i .. samples for dissection. All three sampling tech-
niques have been used previously to detect or :. .... i
densities of pests within a system. In techniques 2 and
3, 140 1 .. buds and 140 vegetative buds were col-
lected for analysis on each sampling date from each
planting. Experimental design was randomized com-
plete block with four replicates per treatment in each
planting. Treatments were blocked by cultivar in the
rabbiteye planting and by clone in the southern high-
Vol. 96, no. 6
SAEZYNSKI AND LIBURD: MONITORINc TECHNIQUES FOR D. oxycoccana
Table 1. Comparison of techniques for monitoring D. oxycoccana in rabbiteye blueberries in Windsor, FL (2002)
Mean SEM D. oxycoccana
Floral buds Leaf buds
Adult Larva Egg Adult Larva Egg
Sampling technique
Yellow sticky boards" 4.0 2.0b 1.3 0.8b 4.0 1 2.0 1.3 1 0.8b
Emergence 72.8 12.2a 104.3 17.5a 2.3 1.3 3.5 1.ab
Dissection 0.0 0.0Ob 135.5 32.4a 173 + 6.3 0.0 0.0 12.0 1 6.4a 13.3 2.0
Means within columns followed by the same letter 0- 0 D t ** : *n s.... > 0.05, LSD test. Analyses were performed on square-root
transformed data, but means shown reflect untransformed data.
aData for yellow sticky boards were identical for floral and leaf bud comparisons because sampling was conducted on the same dates for
these bud types.
bush planting. Experimental plots consisted of 15
bushes and were designated according to treatment.
In both rabbiteye and southern highbush plantings,
buds were collected when floral and leaf buds were
presumed to be most susceptible to D. oxycoccana
infestation, i.e., stages 2-4 of i. .1 bud development
(Spiers 1978) and stages 2-4 of leaf bud development
(NeSmith et al. 1998). In .11 -. plantings, floral
bud and leaf bud development usually occur simulta-
neously. Therefore, in 2002 sampling for both bud
types was conducted on 8, 15, and 19 March, and in
2003, sampling was conducted on 3, 6, and 10 March.
In southern highbush plantings, stages 2-4 of i1. i
bud development ., i ... i .. i bud de-
velopment by -3 wk. In 2002, floral buds were col-
lected from the southern highbush planting on 7, 11,
and18 February, and ,l ..1 .. .. i i. I lI on5, 11,
and 18 March. In 2003, 1i., ,i buds were collected on
3, 7, and 13 February, and leaf buds were collected on
24 February and 3 and 6 March.
Monitoring boards were sampled using the two-
stage visual analysis described in the section for our
colored board experiment. I.. 1i,, traps were
screened for the presence of flies resembling D. oxy-
coccana, and then highlighted specimens were ob-
served under a 10x dissecting microscope to make an
accurate identification. One hundred forty buds per
treatment (35 buds from each replicate) were col-
lected at random for larval emergence and dissection
techniques. Floral and vegetative buds were collected
separately and placed into resealable transparent con-
tainers for transportation back to the laboratory. Buds
collected for monitoring larval emergence were trans-
ferred to 15-cm plastic petri dishes containing moist-
(e. I 1.,:.. .. .. .... i i.. I. I at 27C under a photoperiod
of 14:10 (L:D) h for 10 d. The total number of emer-
gent larvae and adults was recorded. Buds (n = 140)
collected for dissection were dissected under a 10x
dissecting microscope and all life stages of D. oxycoc-
cana found were recorded. Treatments were rotated
among experimental plots on weekly basis. The most
H:1 ... ... technique was determined based on
the abundance of various life stages of D. oxycoccana.
Bud Type Comparison. Data :: i .I from the
dissection technique were used to compare infestation
rates of floral buds and leaf buds collected from both
rabbiteye and southern highbush plantings. Due to
variations in plant phenology, the four bud types (rab-
biteye floral, rabbiteye leaf, southern highbush floral,
and southern highbush leaf) were collected over dif-
ferent time periods. Nonetheless, overall comparisons
were made to determine which buds were most sus-
ceptible to D. .... : ... In 2002 and 2003,
bud types were compared for the presence of eggs and
larvae. In addition, larvae were also categorized by
instar in 2003.
Data Analysis. Data from all three studies were
square-root transformed to account for deviations
from normality and then subjected to an analysis of
variance (ANOVA) .11 -I :)y mean separation with
least significant difference (LSD) tests (SAS Institute
2001). Data also were subjected to repeated measures
analysis (PROC MIXED, SAS Institute 2001) to ex-
amine the interaction effect between treatment and
time (sampling dates) throughout the duration of
each experiment. When significant interaction effects
were noted, further analysis was conducted to deter-
mine the order of treatment efficacy for each sampling
date. Means were considered significantly different
when Pvalues were 0.05. The untransformed means
and standard errors are presented in tables.
Results
Unbaited Colored Traps. In 2002, there were no
significant differences in captures of D. oxycoccana
adults on unbaited sticky boards of various colors in
either the rabbiteye (F = 2.2; df = 3, 9; P = 0.16) or
the southern highbush (F = 2.2; df = 3, 9; P = 0.16)
plantings. Overall, the number ofD. .... ... 11 .
caught on traps averaged less than one fly per trap
during each sampling date in 2002. In 2003, trap cap-
tures were higher, averaging eight to nine 11.. per trap
during each sampling date. Still, we found no differ-
ences in captures of adults on the various colors of
traps (F = 3.0; df = 3, 9; P = 0.09).
Monitoring Techniques. In 2002, the emergence
technique was significantly more effective in detect-
ing D. oxycoccana adults in rabbiteye floral buds com-
pared with unbaited yellow sticky boards or dissection
techniques (F = 53.5; df = 2, 6; P < 0.01) (Table 1).
Emnergence and dissection techniques performed
. ,. .11 well for detecting D. oxycoccana larvae in
, 1i. floral buds, and both techniques detected
_...,i :,,li more larvae compared with unbaited yel-
low sticky boards (F = 57.1; df = 2, 6; P < 0.01) (Table
December 2003
JOURNAL OF ECONOMIC ENTOMOLOGY
Table 2. Comparison of techniques for monitoring D. oxycoccana in southern highbush blueberries in Windsor, FL (2002)
Mean I SEM D. oxycoccana
Floral buds Leaf buds
Adult Larva Egg Adult Larva Egg
Sampling technique
Yellow sticky boards 1.0 0.7 0.0 O.Ob 0.8 0.5 0.0 O.Ob
Emergence 1.4 0.9 2.0 1.2b 0.5 1 0.3 0.8 0.5ab
Dissection 0.0 0.0 16.8 + 4.7a 73 1 4.6 0.0 1 0.0 5.0 + 2.6a 56.0 11.3
Means within columns followed by the same letter r .. .. 1 *....
transformed data, but means shown reflect untransformed data.
1). There were no significant differences among sam-
pling techniques for detecting adults in rabbiteve leaf
buds (F = 2.3; df = 2, 6; P = 0.18) (Table 1). Among
all of the plant material we analyzed, the only sampling
technique capable of detecting D. oxycoccana eggs was
dissection (Tables 1-4).
The number ofD. oxycoccana adults detected using
our three techniques did not differ in southern high-
bush floral buds (F = 1.8; df = 2, 6; P = 0.25) and leaf
(F = 1.2; df = 2, 6; P = 0.36) (Table 2). However, the
dissection technique was significantly more effective
in detecting D. oxycoccana larvae in southern highbush
floral buds compared with the emergence technique
or unbaited yellow sticky boards (F = 38.0; df = 2, 6;
P < 0.01) (Table 2). Six times more D. oxycoccana
larvae were detected in leaf buds by dissection than by
emergence techniques (Table 2).
In 2003, infestation of i. buds by D. oxycoccana
in the rabbiteye planting was slightly higher in 2003
than in 2002. As in 2002, the emergence technique was
significantly more effective in detecting D. oxycoccana
adults in I,. buds compared with either II
boards or dissection (F = 101.0; df = 2, 6; P < 0.01)
(Table 3). However, in our analysis of leaf buds, yel-
low sticky boards were significantly more effective in
detecting adults compared with emergence or dissec-
tion techniques (F = 28.2; df = 2, 6; P < 0.01) (Table
3). Importantly, there were significant interaction ef-
fects between treatment and time (sampling dates)
for the detection of D. oxycoccana adults in rabbiteye
floral buds (F = 8.6; df = 6, 18; P < 0.01). That is,
treatment efficacy varied over the three sampling
dates. -.I '.'I ,, ,. II sticky boards were not ef-
fective for detecting D. oxycoccana adults early in the
season (3 and 7 March) but were significantly more
: i ,- > 0.05, LSD test. Analyses were performed on square-root
effective than dissection techniques later in the season
(10 March) (F = 47.9; df = 2, 6; P < 0.01). Again,
significant interaction effects between treatment and
sampling dates were observed for rabbiteye leaf buds,
whereas II sticky boards were not effective for
detecting adults on 3 March, but they were more
effective than dissection and emergence techniques
on 6 and 10 March (F = 6.6; df = 6, 18; P < 0.01).
Similar numbers of )D oxycoccana larvae were de-
tected using emergence and dissection techniques in
rabbiteye floral and leaf buds (Table 3). As in 2002,
some larvae were detected on sticky boards, although
their incidence was sporadic.
In the southern highbush planting, the emergence
technique was significantly more effective in detect-
ing D. oxycoccana adults in floral and leaf buds com-
pared with II .. sticky boards or dissection (F =
169.8; df = 2, 6; P < 0.01) (Table 4). Similarly, our
emergence technique was .i;L .... .... 0. 1 .
in detecting D. oxycoccana larvae in southern highbush
floral buds compared with the dissection technique
(F = 31.4: df = 2. 6: P < 0.01) (Table 4). However,
sampling techniques did not :1,i -t ., detecting larvae
in southern highbush leaf buds (F = 3.8; df = 2, 6; P =
0.09). In 2003, we did not record any D. oxycoccana
eggs in southern highbush floral buds. However, a
substantial number of D. oxycoccana eggs were de-
tected in southern highbush leaf buds.
On several occasions, we noted the presence of
adult parasitic wasps (Hymenoptera: Platygastridae)
in buds collected for our emergence and dissection
treatments. However, we never witnessed the emer-
gence of this wasp from D. oxycoccana larvae. In ad-
dition, D. oxycoccana adults reared in the laboratory
for this study indicated asex ratio of60 -70% females.
Table 3. Comparison of techniques for monitoring D. oxycoccana in rabbiteye blueberries hi Windsor, FL (2003)
Mean I SEM D. oxycoccana
Floral buds Leaf buds
Adult Larva Egg Adult Larva Egg
Sampling technique
Yellow sticky boards 12.8 1 3.4b 0.3 0.3b 12.8 3.4a 0.3 0.3b
Emergence 122.5 13.0a 175.0 18.7a 4.3 1.7b 6.0 2.1a
Dissection 0.0 1 0.c 182.3 15.5a 27.5 7.9 0.0 1 0.0c 4.0 1 2.Oab 31.3 1 8.2
Means within columns followed by the same letter .. .... .... : : ..* > 0.05, LSD test. Analyses were performed on square-root
transformed data, but means shown reflect untransformed data.
a Data for yellow sticky boards were identical for floral and leaf bud comparisons since sampling was conducted on the same dates for these
bud types.
Vol. 96, no. 6
SARZYNSKI AND LIBURD: MONITORING TECHNIQUES FOR D. oxycoccana
Table 4. Comparison of techniques for monitoring D. oxycoccana in southern highbush blueberries in Windsor, FL (2003)
Mean SEM D. oxycoccana
Floral buds Leaf buds
Adult Larva Egg Adult Larva Egg
Sampling technique
Yellow sticky boards 0.3 0.3b 0.0 0.0c 0.3 0.3b 0.0 0.0
Emergence 19.8 3.5a 28.0 5.1a 4.0 2.7a 5.8 3.8
Dissection 0.0 + 0.0b 13.8 1 4.4b 0.0 0.0 0.0 0.0b 6.3 3.6 52.5 15.5
Means within columns followed by the same letter ... -. 1 *....
transformed data, but means shown reflect untransformed data.
Bud Type Comparison. In 2002, there were signif-
icantly more D. oxycoccana eggs in southern highbush
leaf buds compared with any other bud types (F = 9.9;
df = 3, 9; P < 0.01) (Table 5). Eggs were found least
often in southern highbush floral buds in both 2002
and 2003. The number of eggs in southern highbush
floral buds was similar to that of rabbiteye floral and
leaf buds in 2002. Similar numbers of D. oxycoccana
eggs were record .1 .. .1.1 .:. floral and .: .. I in
both years (Tables 5 and 6). We recorded .....- .....
more D. oxycoccana larvae in rabbiteye floral buds
compared with any other bud type in 2002 (F = 39.7;
df = 3, 9; P < 0.01).
In 2003, the highest number of D. oxycoccana eggs
was recorded in southern highbush leaf buds (Table
6). .-* i F... more first instars were detected in
rabbiteve floral buds compared with any other bud
types (F = 18.2; df = 3, 9; P < 0.01), followed by
southern highbush floral buds, which had significantly
more first instars than leaf buds of southern highbush
plants (F = 182; df = 3, 9; P < 0.01) (Table 6). Second
instars were significantly more abundant in rabbiteye
floral buds compared with any other bud types (F =
485.0; df = 3, 9; P < 0.01) (Table 6). Similar results
were recorded for third instars.
Discussion
Our studies indicate thatD. .... .....1.1. 1 ..not
respond i : .. 11 a the various colors of unbaited
sticky board traps we evaluated. Currently, unbaited
sticky traps seem to be an ineffective tactic for mon-
itoring D. oxycoccana populations. However, the use of
sticky traps for monitoring D. oxycoccana adults may
Table 5. Infestation of rabbiteye and southern highbush blue-
berry buds by D. oxycoccana., Windsor, FL (2002)
Mean S SEM of D. oxycoccana
Bud type per 420 buds
Egg Larva
Rabbiteye floral 17.3 1 6.3b 133.5 32.4a
Rabbiteye leaf 13.3 2.0b 12.0 + 64b
Southern highbush floral 7.3 4.6b 16.8 4.7b
Southern highbush leaf 56.0 11.3a 5.0 2.6b
Means within columns followed by the same letter are not signif-
icantly different, P > 0.05, LSD test. Analyses were performed on
square-root transformed data, but means shown reflect untrans-
formed data.
: ,,. > 0.05, LSD test. Analyses were performed on square-root
be improved by incorporating a hiring device, either
a sex pheromone or a host-volatile compound, or by
changing trap height or type. A better understanding
of olfactory stimuli and responses in 1). oxycoccana
may compliment the use of visual stimuli in future
monitoring efforts. The relative increase in mean trap
counts from 2002 to 2003 was likely due to higher
pressure of D. oxycoccana in the field and also to the
better condition of board-preserved specimens, which
was facilitated by replacing traps more frequently.
Overall, identification of D. oxycoccana was difficult
due to several key factors: small size (-2 rmm), the
sticky surface of the traps, specimen degradation in
the field, poor preservation of distinguishing charac-
teristics. and the presence of other i.- within the
family Cecidomyiidae. The sticky surface on the mon-
itoring boards often damaged the integrity of key
morphological features, including wing venation, mi-
crotrichia, and antennal segmentation, which are use-
ful for accurately 1. ,ili .,_ D. oxycoccana adults.
i) ...i, .: x ... was marginally enhanced on the white
boards, largely because of the color contrast with the
insect abdomen, which is often bright orange in D.
oxycoccana females.
In our sampling techniques study, we found that the
emergence technique generally performed better
than unbaited ii sticky traps or the dissection
technique for detecting D. oxycoccana adults. Emer-
gence and dissection techniques performed ,i Ii:.
well for detecting D. oxycoccana larvae. The presence
of larvae on sticky boards was likely due to wind
disturbances as the larvae were dropping from buds to
pupate in the soil. In contrast, eggs were only detected
by :.. I.li; dissecting infested buds. Although bud
dissection is time consuming, the ability to detect D.
oxycoccana eggs is important because this information
could be used by blueberry growers to make insecti-
cide l.i.1L. .. either before eggs hatch or before
additional females begin laying eggs. Ultimately, it
may be possible to manage D. oxycoccana infestations
effectively using a limited number of properly timed
sprays.
The phenological differences between rabbiteye
and southern highbush blueberry plants may account
for differences in infestation by D. oxycoccana. In gen-
eral, 11. bud development of most southern high-
bush cultivars occurs before leaf bud development
and before populations of D. oxycoccana peak in the
field. Perhaps this phenological .1 i.i ... is the rea-
December 2003
JOURNAL OF ECONOMIC ENTOMOLOGY
Table 6. Infestation of rabbiteye and southern highbush blueberry buds by D. oxycoccana, Windsor, FL (2003).
SMean SEM of D. oxycoccana per 120 buds
Bud type
Egg First instar Second instar Third instar
Rabbiteye floral 27.5 7.9a 61.0 16.9a 108.0 6.3a 12.3 -4.7a
Rabbiteye leaf 313 1 8.2a 3.8 1.9bc 0.3 0.3b 0.0 O.Ob
Southern highbush floral 0.0 O.0b 13.5 4.3b 0.3 0.3b 0.0 0.0b
Southern highbush leaf 52.5 15.5a 1.0 OAc 0.0 0 Ob 0.0 1 0.0b
Means within columns followed by the same letter are not significantly different, P 0.05, LSD test. Analyses were performed on square-root
transformed data, but means shown reflect untransformed data.
son why southern highbush floral buds had the fewest
number of D. oxycoccana eggs in both years that we
sampled. Climatic conditions vary greatly from year to
year during the spring growing season in Florida,
which may influence D. oxycoccana densities. It is
possible that susceptible stages of floral bud develop-
ment may coincide with D. oxycoccana pressure. For
instance, a mild winter may 11 D. oxycoccana pop-
ulations to build up early in the blueberry production
season, whereas a hard freeze in February or March
may kill any D. oxycoccana that are already developing
inside infested buds.
Overall, we recorded the highest incidence of D.
oxycoccana eggs in southern highbush . I both
in 2002 and 2003. However, larval infestation of south-
ern highbush leaf buds never exceeded that of the
other bud types we evaluated. This phenomenon may
indicate that survivorship of D. oxycoccana infesting
southern highbush cultivars may be reduced com-
pared with rabbiteye cultivars. The reason why south-
ern highbush flower buds contained more eggs yet
fewer larvae is unknown, but it is .1 that the
structure or the nutritional value of .11..:. buds is
more conducive to the development of D. oxycoccana
than southern highbush buds. The significantly higher
number of D. oxycoccana larvae in rabbiteye 1. 1
buds compared with other bud types further supports
this idea. However, laboratory studies must be con-
ducted to prove or disprove these hypotheses.
The observation of platygastrid wasps in buds col-
lected for our emergence and dissection treatments
was notable. Although we never witnessed the emer-
gence of these wasps from D. oxycoccana larvae, their
role as a potential parasitoid was recognized.
The number of eggs in the various types of buds we
compared may lend insight regarding the oviposition
preference by D. oxycoccana females. One factor that
may vary from one bud type to another is surface lipid
composition, which may I.... i plant examination
and egg-laying behavior. Eigenbrode and Espelie
(1995) discuss the variation in epicuticular waxes of
plants within and among species, indicating that their
presence may not only prevent plant dehydration but
also mediate interactions between plants and insects.
In another cecidomyiid, the Hessian fly, Mayetiola
destructor (Say), laboratory studies showed that the
extractable surface lipids of wheat increased the num-
ber of eggs laid by females compared with chloroform
controls (Harris and Rose 1990). Comparisons be-
tween rabbiteye and southern highbush surface lipid
composition, as II as various cultivars within these
species, may complement future laboratory studies to
determine oviposition preference by D. oxycoccana
females.
Overall, our studies demonstrate that D. oxycoccana
adults show little .-. .. to various colors of sticky
boards in the field. The emergence technique was the
most :: ,, tool we evaluated for detecting D. oxy-
coccana adults, whereas emergence and dissection
techniques were .*:, .11 effective for detecting D.
oxycoccana larvae. Dasineura oxycoccana eggs are eas-
ily detected in infested buds by using a dissection
technique, which may be valuable to growers if they
are able to make insecticide applications before larvae
hatch or before females begin laying additional eggs.
Acknowledgments
We thank Carolyn Mullin, Rajya Pandey, Kenna Mac-
Kenzie, and Ashley Johnson (University of Florida) for as-
sistance in (. II field data. We are grateful to Alto
. ,-i.,. and Donna Miller for .oi .... us to conduct our
experiments in their plantings. We thank Heather McAus-
lane and Paul Lyrene (University of Florida) for critical
reviews of the manuscript. 1 i ... .... .. i l.by
USDA Pest Management Alternative grant No.731497113.
This manuscript is Florida Agricultural Experiment Station
Journal Series No. R-09741.
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Received for publication 5 June 2002; accepted 9 September
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December 2003
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