LABORATORY EVALUATION OF SELECTED INSECTICIDES ON FIELD-COLLECTED POPULATIONS OF BOLLWORM AND TOBACCO BUDWORM LARVAE--UPDATE 2005

摘要

Tobacco budworm and Bollworm larvae were collected from a variety of host crops throughout the cotton belt of Georgia and evaluated for susceptibility to MVP II~(R), Cypermethrin and spinosad during the 2005 season. Results were compared to historicaldata collected throughout a ten-year study period beginning in 1995. During the ten-year study period, tobacco budworm populations have remained susceptible to MVPII~(R), and as expected, bollworm larvae were more tolerant to the effects of MVPII~(R) ascompared to tobacco budworm larvae. Average MVPII~(R) LC50s for bollworm larvae have more than doubled during the ten-year study period. Although cypermethrin remains an effective insecticide to control bollworm larvae, LC50s for cypermethrin against tobacco budworm larvae have steadily increased during the ten-year study period and are comparable to an LC50 obtained for a laboratory-selected pyrethroid-resistant strain. This observation was confirmed in one field-collected tobacco budworm strain usingan alternative topical application bioassay. Furthermore, average cypermethrin LC95 values for tobacco budworm have steadily increased during the ten year study period. Spinosad has remained an effective insecticide against both bollworm and tobacco budworm larvae.