Laboratory Evaluation of Selected Insecticides on Field-Collected Populations of Bollworm and Tobacco Budworm Larvae-2017 Update

Bollworm (CEW) and tobacco budworm (TBW) larvae and adults were collected from a variety of host crops and evaluated for susceptibility to MVP II^®, cyperemthrin, and spinosad (Tracer^®) during the 2017 season. Results were compared to historical data collected throughout a twenty three-year study period which began in 1995. Throughout the study period, the susceptibilities of CEW and TBW larvae to MVPII^® have been highly variable. MVPII^® LC₅₀ values for both CEW and TBW were highest during the 2010 season. However, for field-collected TBW larvae, MVPII^® LC₅₀ values during the 2011-2017 seasons have been some of the lowest values recorded. On the other hand, MVPII^® LC₅₀ values for populations of CEW collected during the past three seasons have been some of the highest values recorded during the study period. Although cypermethrin remains an effective insecticide to control CEW larvae, average LC₅₀ values have fluctuated; however, CEW LC₅₀s for cypermethrin during the past two seasons were among the highest values recorded since 2011. In general, the effectiveness of cypermethrin for the control of TBW larvae has continued to decline. Data obtained from adult vial tests (AVT) supported the larval studies and indicated that CEW and TBW populations in Georgia were becoming less susceptible to the effects of cypermethrin (pyrethroid insecticides). Spinosad (Tracer^®) has remained effective against CEW and TBW larvae throughout the study period.