Insecticidal Control of Caterpillar Pests of Cole Crops Alton N. Sparks, Jr. and David G. Riley, University of Georgia, Tifton, Georgia

INTRODUCTION

Cole crops in Georgia may be attacked by a wide variety of insect pests including aphids, whiteflies, thrips and beetles. However, caterpillars are the key pests of this crop group. Of the various caterpillars that attack cole crops, the diamondback moth has generally been of greatest concern because of difficulty of control and its potential for development of resistance to insecticides. Most of the recently developed insecticides for this crop group target this pest and have generally shown excellent efficacy against diamondback moth. However, diamondback moth is not the only caterpillar that attacks cole crops, is seldom the only species in an infested field, and has actually been less pestiferous in the last two years than several other caterpillar species. Thus, efficacy data against these other species of caterpillars is needed to aid producers in pesticide selection decisions.

This poster presents results of small plot studies conducted to evaluate the efficacy of ‘newer’ insecticides against common caterpillar pests of cole crops in Georgia. Species targeted in these tests included the cabbage looper and imported cabbageworm which are common pests throughout Georgia and can occur in damaging populations throughout the year in south Georgia. Cross-striped cabbageworm, which is a problem in the fall in north Georgia, was targeted in one test.

MATERIALS AND METHODS

Four of the tests were conducted at University of Georgia research farms in Tifton, Georgia (south Georgia). The fifth test was conducted at the Georgia Mountain Research and Education Center in Blairsville, Georgia (north Georgia). Plot size and application dates were as follows:

Test Plot Size Application dates

Cabbage, 2004 2 rows (16 in centers) by 24 feet 1, 8, 16, 28 Oct., 6 Nov.

Collards, 2004 2 rows (36 in centers) by 21 feet 29 Sept., 8, 16 Oct.

Cabbage, 2005 2 rows (36 in centers) by 40 feet 17, 25 April, 2, 13, 20 May

Collards, 2005 1 row (35 in) by 25 feet 5, 19, 29 July

Collards, 2005, Blairsville 1 row (36 in) by 20 feet 1, 16 Aug.

Treatments were applied with a CO2 pressurized backpack sprayer (60 PSI) in a total volume of 30 GPA. The Cabbage, 2004 test was treated with 2 hollow cone nozzles per bed. All other tests were treated with 3 hollow cone nozzles per row, with one nozzle over-the-top and one on each side of the row on drops. Insecticides evaluated were:

Trade Name Common name Rate per acre (formulated / lb AI) Manufacturer

Avaunt 30WDG indoxacarb 3.5 oz/ 0.065 DuPont

Intrepid 2F methoxyfenozide 8 oz / 0.125 Dow AgroSciences

Proclaim 5SG emamectin benzoate 3.2 oz / 0.01 Syngenta

SpinTor 2SC spinosad 4 oz / 0.0625 Dow AgroSciences

Tesoro 4EC pyridalyl 6.4 oz / 0.2 Valent

Rimon 0.83EC novaluron 9-12 oz / 0.058-0.078 Chemtura

Warrior 1CS lambda-cyhalothrin 3.84 oz / 0.03 Syngenta

(BAS 320 I) 2SC metaflumizone 13.7 oz / 0.214 BASF

All tests were visually sampled, with caterpillars per plant counted on 5 randomly selected plants per plot. In two tests, number of plants damaged were counted in each plot. Plants were classified as minor damage (outter leaves with feeding damage) or severe damage (large sections of leaves or terminal of plant damaged). In the Cabbage, 2005 test a final efficacy rating was conducted with a 1 = excellent control, 2 = good control, 3 = obvious control but not acceptable, 4 = poor control but some suppression, and 5 = no control.

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).

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Cabbage Looper: Most of the products evaluated provided good control of cabbage looper, with the exceptions of Proclaim and Tesoro. This weakness was most evident in the Cabbage, 2004 trial. Although not consistently statistically different, the same trends appeared in both 2005 trials. SpinTor and BAS 320I both showed high looper densities at 9 days after treatment in the Collards, 2005 trial; however, it appears that this likely resulted from shorter residual control rather than poor control.

Imported cabbageworm: All products tested appeared to provide good to excellent control of imported cabbageworm. Minor statistical differences that occurred among insecticide treatments were likely a result of different residual control levels rather than efficacy. At 9 days after the first treatment in the Collards, 2005 trial BAS 320I and Proclaim failed to separate from the check (a similar trend occurred in the Cabbage, 2005 trail at 10 DAT-3), but provided good control on dates nearer application dates.

Cross-striped cabbageworm: All products except BAS 320I provided similar levels of control. BAS 320I failed to separate from the check at 7 DAT-1 and was not in the lowest statistical rating at 6 DAT-2, but provided excellent control at 4 DAT-1. As with the previous pests, this may have resulted from short residual control.

ABSTRACT

Diamondback moth has been the target of many of the most recently registered insecticides for cole crops. While this pest is of primary concern, other Lepidopterous pests do occur and require control. A series of small plot trials were conducted to evaluate the efficacy of these insecticides against other common caterpillar pests of cole crops. Avaunt, Intrepid, SpinTor, Rimon and Warrior (used as a standard) provided the most consistent control of cabbage looper, imported cabbageworm and cross-striped cabbageworm larvae. BAS 320I appeared to provide good control of all three species, but showed indications of shorter residual activity. Proclaim and Tesoro provided good control of both cabbageworm species, but showed less activity against cabbage loopers as compared to the other insecticides.

Efficacy ratings and damaged plants: All treatments provided some level of damage reduction as compared to the check. General trends across all three tests with ratings indicate increased level of damage with BAS 320I, Tesoro, and Proclaim. This damage most likely resulted from a slight weakness on loopers with Tesoro and Proclaim and a shorter residual control with all three products.

RESULTS AND DISCUSSION