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Toxicity of Acephate, Cypermethrin, and Oxamyl to Tarnished Plant Bugs in Vial Bioassays and Cage Studies on Cotton

J.H. Pankey, B.R. Leonard, J.B. Graves, E. Burris


Tarnished plant bugs were collected from various hosts and locations throughout Louisiana to monitor for tolerance to a carbamate, organophos-phate, and pyrethroid insecticide. Insects were tested using the residual film vial bioassay. Field tests also were conducted with the same insecticides by caging tarnished plant bugs on treated cotton terminals. Tarnished plant bugs collected April through July of 1994 and 1995 usually had significantly lower LC50 values (4-37x) than collections from August when tested with cypermethrin. LC50's for acephate ranged from 0.93 g/vial (Franklin Parish in June, 1995) to 6.49 g/vial (Richland Parish in June, 1994) a 7X difference. The lowest LC50 for oxamyl was 0.92 g/vial (Caddo Parish from alfalfa, June 1995), while the highest value was 4.84 g/vial (Franklin Parish from cotton, August 1995), a 5X difference. In the field tests, tarnished plant bug adult mortality was significantly higher on acephate and oxamyl treated terminals compared to cypermethrin treated terminals when test insects were caged 2 hours after treatment (HAT). There were no significant differences in mortality among treatments when nymphs were caged 2 HAT or when adults or nymphs were caged 2 days after treatments (DAT). When caged 2 HAT, there was no significant difference between adult and nymph mortality for each insecticide. However, when caged 2 DAT, adult mortality was significantly lower than nymph mortality for each insecticide.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 882 - 887
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998