Response of Silverleaf Whitefly (Homoptera: Aleyrodidae) to Bifenthrin and Endosulfan by Vial Bioassay in Florida, Georgia and Texas

Median lethal concentration (LC50) values of bifenthrin and endosulfan were determined for dead and moribund + dead categories for adults of the silverleaf whitefly, Bemisia argentifolii (Bellows and Perring) (formerly sweetpotato whitefly, B. tabaci (Gennadius), strain B), in 3-h vial bioassays in Florida, Georgia, and Texas in 1991 and 1992. For the moribund + dead category in Florida, LC50 values for bifenthrin ranged from 0.00076 to 1.48 μg/vial, a 1,947-fold difference. An LC50 as high as 128.1 μg bifenthrin/vial for adults from cabbage in Texas was determined for the dead category. For endosulfan in Florida, LC50 values of the moribund plus dead categories for endosulfan ranged from 0.04 to 35.6 μg/vial, an 890-fold difference. An LC50 as high as 119.7 μg endosulfan/vial was determined for adults from cotton in Texas for the dead category. The wide ranges of LC50 values for both insecticides suggest the presence of resistant and susceptible whiteflies in all three states.