EFFICACY OF SELECTED INSECTICIDES
AGAINST PICKLEWORM IN SQUASH
Alton N. Sparks, Jr.
University of Georgia Cooperative Extension
Department of Entomology
Tifton, Georgia 31793
asparks@uga.edu
Introduction
Squash grown in Georgia during the spring production season frequently escapes
damage by the pickleworm, as this species is a migratory pest and must reinvade Georgia
from the south each year. Normally pickleworm does not appear until June or July, and
most of the Spring crop is produced with little need for insecticides for this pest.
However, the late-spring crop and fall crop requires multiple applications of insecticides
to protect fruit from this boring caterpillar. Eggs are laid on or near the fruit and larvae
will bore into fruit shortly after hatching. Once inside the fruit, larvae are protected from
insecticide sprays. Thus, insecticides are generally applied on a schedule during those
times of the year when pickleworm is present. This test was conducted to evaluate
standard and selected new insecticides for efficacy against pickleworm in squash. A
combination treatment of a standard pickleworm insecticide and a potential tank mix
partner for silverleaf whitefly was included as these two pests frequently occur together
during the fall production season.
Materials and Methods
A small plot test was conducted at the University of Georgia’s Horticulture Farm
in Tifton, Georgia. A virus resistant squash, Destiny III, was direct seeded on September
1, 2005, with a single row on a 6 foot bed. Drip tape was placed adjacent to the planted
row to provide germination moisture and was used for irrigation. Plots were established
with 25 feet of row per plot. The experimental design was a randomized complete block
with four replications of five treatments. Insecticides, formulations and rates evaluated
were:
Insecticide/formulation
Amount per acre
Pounds AI per acre
SpinTor 2SC
4.3 oz.
0.066
Proclaim 5SG
2.4 oz.
0.0075
Warrior 1CS
3.84 oz
0.03
Warrior 1CS
3.84 oz.
0.03
+ Knack 0.83EC
8.0 oz.
0.05
A non-treated control (Check) was included for comparison. Warrior was included in the
test as a standard treatment, as many of the products used against pickleworm are
pyrethroid insecticides. SpinTor and Proclaim are active against a variety of caterpillar
pests. Knack was included in a combination treatment to evaluate activity against the
silverleaf whitefly. Insecticide treatments were applied with a CO2 pressurized backpack
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sprayer (60 PSI) calibrated to deliver 30 GPA, with three hollow-cone nozzles per row (1
over-the-top, 2 on drops). Treatments were initiated at first detection of fruiting structures
in the field. Silverleaf symptoms were already severe at this point. Treatments were
applied on 26 Sept and 3, 9 and 15 Oct., 2005.
All fruit of harvestable size were collected from each plot on each harvest date.
Fruit were examined for damage from pickleworm and counted. Fruit were also examined
on each harvest date for potential differences in color resulting from control of silverleaf
whitefly. When potential differences were noted (last two sample dates), an average fruit
color was assigned for each plot, with a 2 being a near white fruit, a 3 a cream colored
fruit and a 5 a bright yellow fruit as expected with yellow squash (a 4 is intermediate of
the cream and yellow colors; 1/4 intervals were used in the rankings). A three would
likely be a marketable color, but a 4 or better would be preferred. Data were analyzed
with the PROC ANOVA procedure of PC-SAS. Where significant differences were
detected (P<0.05), means were separated with LSD (P=0.05).
Results and Discussion
All insecticide treatments provided reduction in pickleworm damage as compared
to the check (Table 1). Warrior generally provided the greatest numerical control although
it was never significantly different than SpinTor. Proclaim did contain significantly more
damage than the other insecticide treatments on the last sample date.
At initiation of harvest, all fruit were ‘bleached’ from silverleaf whitefly (would
have been rated a color of <3). The Knack treatments provided slightly improved color by
the Oct. 10 harvest, but numerical data was not collected on this date. On the last two
harvest dates, the Knack treatment (Warrior+Knack) provide significantly improved fruit
color, with average ratings at or above 3.5, while all other treatments were below 3 (Table
2).
Visual observations of foliage during this test also support the efficacy of Knack
for management of silverleaf symptoms. On Sept. 30, all plots were observed to exhibit
heavy silvering of foliage throughout the plots. On the final harvest date, the plots
receiving Knack treatments could be easily identified from the end of the field, as they
were the only plots with green foliage.
While all of the insecticides evaluated for pickleworm provided significant
control, the pyrethroid insecticides would easily prove the most economical. Knack
proved efficacious against silverleaf whitefly, but as expected, the slow response
indicates a need to use this product in a more preventative approach rather than the
curative approach used in this test.
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Table 1. Number of pickleworm damaged fruit per plot, pickleworm efficacy trail in
squash, Tifton, Georgia, 2005.
Treatment
Number of fruit with pickleworm damage per plot
Sept. 30
Oct. 5
Oct. 7*
Oct. 10
Oct. 14
Oct. 17
Total
Check
0.50 a
3.25 a
2.25 a
0.75 a
8.00 a
8.25 a
23.00 a
SpinTor
0.75 a
1.25 a
1.75 a
0.25 a
1.00 b
1.25 c
6.25 bc
Proclaim
0.00 a
1.25 a
0.50 a
0.25 a
2.00 b
3.25 b
7.25 b
Warrior
0.00 a
0.50 a
0.00 a
0.00 a
0.50 b
0.25 c
1.25 cd
Warrior
0.00 a
0.50 a
0.25 a
0.00 a
0.25 b
0.00 c
1.00 d
+ Knack
Means within columns followed by the same letter are not significantly different (LSD;
P=0.05).
*Differences were significant at P = 0.1.
Table 2. Percent pickleworm damaged fruit and fruit color ratings, pickleworm
efficacy trail in squash, Tifton, Georgia, 2005.
Treatment
Check
Percent of total fruit with
pickleworm damage
25.4 a
Average fruit color rating
Oct. 14
Oct. 17
2.13 b
2.56 b
SpinTor
5.2 bc
2.06 b
2.50 b
Proclaim
8.7 b
2.00 b
2.33 b
Warrior
1.1 c
2.31 b
2.69 b
Warrior + Knack
0.9 c
3.50 a
3.69 a
Means within columns followed by the same letter are not significantly different (LSD;
P=0.05).
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