EFFICACY OF SELECTED INSECTICIDES AGAINST MELONWORM ON
SQUASH
Alton N. Sparks and David G. Riley
Dept. of Entomology
University of Georgia
P.O. Box 1209
Tifton, GA 31793
Introduction
Melonworm and pickleworm are key pests of squash and pumpkins grown in the fall in
Georgia. These are migratory pests that generally arrive in the late summer or early fall.
Moth flights into an area can result in very rapid population increases and severe yield
losses. The melonworm is considered more of a foliage feeder but will readily feed on
fruit in the later instars, particularly after defoliation limits leaf availability. Pickleworm
will also feed on leaves but readily bores into fruit even in the early instar stages. Two
small plot trials were conducted at the University of Georgia’s Lang Farm in Tifton,
Georgia, to evaluate the efficacy of selected insecticides against caterpillar pests of
squash. The primary target of this test was the pickleworm; however, the predominant
pest present in both tests was the melonworm.
Materials and Methods
Test I
A virus resistant squash, Destiny III, was direct seeded for this test with two rows planted
on 6 foot beds. Because of stand establishment problems, plants were transplanted to
establish good stands on single rows of each bed (plants moved from the row with the
thinnest stand to fill in thin spots in the row used for the test). Plot size was one row by
24 feet and treatments were arranged in a randomized complete block design with four
replications. Insecticide treatments in test I were:
Avaunt 30WG at 0.045 lb AI/ac and 0.064 lb AI/ac
SpinTor 2SC at 0.039 lb AI/ac and 0.067 lb AI/ac
Intrepid 2F at 0.125 lb AI/ac
Proclaim 5SG at 0.0075 lb AI/ac
Mustang Max 0.8EC at 0.05 lb AI/ac
Non-treated check
All insecticide treatments were tank mixed with Dyne-Amic at 0.5 % v/v. Insecticide
treatments were applied on August 19 and 25 and September 1 with a CO2 pressurized
(50 PSI) backpack sprayer calibrated to deliver 30 GPA. Treatments were broadcast with
3 hollow-cone ceramic nozzles per row (one over-the-top, one on drops on each side of
row). The entire test was treated with an Admire drench on August 18 for silverleaf
whitefly.
Foliage feeding was evident prior to and during harvest in test I. Inspection of foliage
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indicated this damage resulted from an infestation of melonworm. To evaluate efficacy of
the insecticides, all plants in each plot were visually examined and the number of plants
damaged by caterpillars in each plot was recorded. At harvest maturity, all fruit of
harvestable size were collected on each harvest date and were visually inspected for
caterpillar feeding. The total number of fruit harvested and number damaged were
recorded for each plot. All data were analyzed with the PROC ANOVA procedure of PCSAS. Where significant differences were detected (P<0.05), means were separated with
LSD (P=0.05).
Test II
Squash was direct seeded for this test with two rows planted on 6 foot beds. Plot size was
two rows (one 6 ft bed) by 24 feet. Treatments were arranged in a randomized complete
block design with four replications. Insecticide treatments in this test were:
Avaunt 30WG at 0.045 lb AI/ac and 0.064 lb AI/ac
SpinTor 2SC at 0.063 lb AI/ac
Intrepid 2F at 0.125 lb AI/ac
Proclaim 5SG at 0.0075 lb AI/ac
Mustang Max 0.8EC at 0.05 lb AI/ac
Non-treated check
All insecticide treatments were tank mixed with Dyne-Amic at 0.5 % v/v. Treatments
were applied on September 23 and October 1, 6 and 15 with a CO2 pressurized (50 PSI)
backpack sprayer calibrated to deliver 30 GPA. Applications were broadcast with three
hollow-cone ceramic nozzles per row (one over-the-top, one on drops on each side of the
row). In addition to the tested insecticides, oil was applied across the entire test for virus
suppression on Sept. 9, 11 and 19 and Assail was applied to two replications for SLWF
control on Sept. 15.
All fruit of harvestable size were collected and weighed on each harvest date. Fruit were
visually inspected for caterpillar feeding and both the total number of fruit and number
damaged were recorded for each plot. All 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
Test I:
Yields in this test were poor, and harvest data showed no significant differences in the
number of fruit harvested nor the number of fruit damaged by caterpillars (data not
shown). Overall pest pressure was low; however, all insecticides tested provided
suppression of melonworm populations as evidenced by a significant reduction in the
number of plants damaged by melonworm (Table 1).
Test II:
No significant differences occurred in the number or weight of fruit harvested (data not
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shown). All of the insecticides tested provided a significant reduction in the number of
caterpillar damaged fruit (Table 2).
Overall, all of the insecticides tested in both studies showed similar control of
melonworm.
Table 1. Number of plants per plot damaged by caterpillars, melonworm efficacy
trial I, Tifton, Ga., 2003.
Number of damaged plants per plot
Treatment
8/22
8/26
8/29
Check
1.50 a
1.75 a
4.75 a
Mustang Max
0.50 a
0.50 b
0.25 b
Intrepid
0.00 a
0.00 b
0.50 b
Proclaim
0.00 a
0.00 b
0.75 b
SpinTor 0.039
0.00 a
0.25 b
0.25 b
SpinTor 0.067
0.00 a
0.00 b
0.50 b
Avaunt 0.045
0.00 a
0.25 b
0.50 b
Avaunt 0.064
0.00 a
0.25 b
0.25 b
Numbers within columns followed by the same letter are not significantly different (LSD,
P=0.05).
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Table 2. Number of caterpillar damaged fruit harvested per plot, melonworm
efficacy trial II, Tifton, Ga., 2003.
Number of damaged fruit harvested per plot
Total
percent
damaged
Treatment
10/03
10/08
10/14
10/17
10/22
Total
Check
0.25
1.25
5.50
4.00 a
2.00
13.00 a
13.5 a
Mustang
Max
0.00
0.75
0.50
0.25 b
0.25
1.75 b
1.7 b
Intrepid
0.00
2.00
2.00
0.75 b
0.25
5.00 b
5.1 b
Proclaim
0.00
2.00
1.50
0.50 b
0.25
4.25 b
4.2 b
SpinTor
0.00
1.25
0.25
0.50 b
0.25
2.25 b
2.3 b
Avaunt
0.045
0.00
1.50
0.25
0.50 b
0.25
2.50 b
2.3 b
Avaunt
0.25
2.50
0.75
1.00 b
0.00
4.50 b
3.6 b
0.064
Numbers within columns followed by the same letter are not significantly different (LSD,
P=0.05). Columns without letters showed no significant differences.
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