EFFICACY OF SELECTED INSECTICIDES AND INSECTICIDE ROTATIONS
AGAINST CATERPILLAR PESTS OF COLLARDS
Mickey Cummings1 and Alton N. Sparks, Jr.2
University of Georgia
1
Union County Extension Office
185 Welborn St., Box 5
Blairsville, GA 30514
2
Dept of Entomology
P.O. Box 1209
Tifton, GA 31793
Introduction
Several caterpillars are key pests of collards in north Georgia. The diamondback moth (DBM),
Plutella xylostella, and the cabbage looper, Trichoplusia ni, are pests throughout the state. The
cross-striped cabbageworm (CSCW), Evergestis rimosalis, is a key pest only in the northern
portions of the state. Growers rely heavily on insecticides for management of these pests.
Resistance to older insecticide chemistries in the DBM has led some growers to rely exclusively
on a single new chemistry, which greatly increases the potential for development of resistance to
this insecticide. A small plot trial was conducted at the Georgia Mountain Research and
Education Center, near Blairsville, Georgia, to evaluate and demonstrate the efficacy of selected
insecticides and insecticide rotations against caterpillar pests of collards.
Materials and Methods
Collards were transplanted on May 19 into single row plots. Experimental plots were 3 foot wide
(1 row) and 20 ft. long, with a fallow row between plots. Treatments were arranged in a
randomized complete block design with four replications. Treatments evaluated were:
1. SpinTor 2SC at 4 oz/ac
2. SpinTor 2SC at 4 oz/ac rotated with Avaunt 30WDG at 3.5 oz/ac
3. Bacillus thuringiensis (Xentari at 1 lb/ac)
4. Diamond at 12 oz/ac
5. Non-treated Check
All insecticide applications were made with a CO2 pressurized (60 PSI) backpack sprayer
calibrated to deliver 40 GPA. Applications were made with a single row boom with three
hollow-cone nozzles per row (one over-the-top, one on a drop on each side). Application dates
and products used in rotational schemes are presented in Table 1.
Plots were sampled twice per week starting on June 18 for presence of caterpillar pests and signs
of fresh damage (fresh holes or droppings). Caterpillar species present in the test included
diamondback moth (DBM), loopers, and cross-striped cabbageworm (CSCW). Each species was
counted separately. Plots were visually searched and numbers reported are the average number
of larvae or fresh damage sites per plot (20 feet of row). Data were analyzed with the PROC
GLM procedure of PC-SAS. Where significant differences were detected (P<0.05), means were
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separated with LSD (P=0.05).
Results and Discussion
Results of caterpillar sampling are presented in Tables 2 and 3. No caterpillars were detected
prior to July 2 (data not shown in tables). CSCW were the most abundant pest in the test. They
first appeared in significant numbers July 10 (one week after an application on July 3). Although
no significant differences occurred prior to the next application of insecticides, trends showed
obvious suppression with SpinTor and Diamond on July 10 and 14. All four insecticide
treatments provided good control of CSCW on July 17 and 21 (2 and 6 days after the final
application). DBM and looper populations were low throughout the test, with no significant
differences among treatments on any date. However, trends in the DBM data indicate good
control with all treatments, particularly SpinTor and Diamond, which never exceeded 0.25 larvae
per plot. Looper densities (data not shown) were even lower than DBM, and all treatments never
exceeded 0.25 larvae per plot.
Results of monitoring for fresh damage sites are presented in Table 4. Significant differences
occurred on July 2 and 21. The counts on July 2 show good control with SpinTor (at 5 days after
application on June 27) and Diamond (at 15 days after application on June 17). On July 21 (6
days after the final application) all four treatments showed significant reductions in the number
of fresh feeding sites.
Overall, all insecticide treatments showed good efficacy against the caterpillar pests present in
this test. This clearly demonstrated the potential to use multiple chemistries in a resistance
management program without loss of control.
Table 1. Application dates and insecticides applied:
Insecticide applied on specified date
Treatment
6/17
6/24*
1
SpinTor
Sevin XLR
2
SpinTor
3
4
6/27
SpinTor
7/3
7/8*
7/15
SpinTor
Sevin XLR
SpinTor
Sevin XLR
Avaunt
Sevin XLR
SpinTor
Xentari
Sevin XLR
Xentari
Sevin XLR
Xentari
Diamond
Sevin XLR
Diamond
Sevin XLR
Diamond
5
Sevin XLR
* Sevin was applied for control of flea beetles.
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Sevin XLR
Table 2. Number of cross-striped cabbageworm larvae per plot, Blairsville, Georgia,
2003.
Number of Cross-striped Cabbageworm Larvae per Plot
Treatment
7/02
7/07
7/10
7/14
7/17
7/21
Check
0a
0.00 a
3.00 a
27.75 a
26.50 a
16.00 a
Xentari
0a
0.25 a
2.00 a
13.25 a
4.75 b
0.50 b
Diamond
0a
0.00 a
0.50 a
4.75 a
2.00 b
0.50 b
SpinTor
0a
0.00 a
0.00 a
0.25 a
0.75 b
0.50 b
Spin/Avaunt
0a
0.25 a
3.75 a
16.25 a
3.25 b
0.50 b
Numbers within columns followed by the same letter are not significantly different (LSD, P=0.05).
Table 3. Number of diamondback moth larvae per plot, Blairsville, Georgia, 2003.
Number of Diamondback Moth Larvae per Plot
Treatment
7/02
7/07
7/10
7/14
7/17
7/21
Check
1.50 a
0.25 a
0.50 a
1.25 a
1.00 a
1.00 a
Xentari
0.25 a
0.00 a
0.00 a
0.25 a
0.75 a
0.50 a
Diamond
0.00 a
0.00 a
0.00 a
0.25 a
0.25 a
0.00 a
SpinTor
0.00 a
0.00 a
0.25 a
0.00 a
0.00 a
0.00 a
Spin/Avaunt
0.00 a
0.00 a
0.75 a
1.25 a
1.25 a
0.75 a
Numbers within columns followed by the same letter are not significantly different (LSD, P=0.05).
Table 4. Number of fresh damage sites per plot, Blairsville, Georgia, 2003.
Number of Fresh Damage Sites per Plot
Treatment
7/02
7/07
7/10
7/14
7/17
7/21
Check
2.00 a
0.25 a
0.00 a
6.50 a
0.33 a
18.75 a
Xentari
1.25 ab
0.00 a
0.25 a
0.50 a
0.00 a
1.75 b
Diamond
0.00 b
0.00 a
0.25 a
0.00 a
0.00 a
0.25 b
SpinTor
0.25 b
0.00 a
0.00 a
0.00 a
0.00 a
1.00 b
Spin/Avaunt
1.00 ab
0.00 a
0.00 a
1.75 a
0.00 a
1.25 b
Numbers within columns followed by the same letter are not significantly different (LSD, P=0.05).
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