In field experiments B-strain whitefly, Bemisia tabaci (Gennadius), was susceptible to bifenthrin and endosulfan in the Lower Rio Grande Valley (LRGV), Weslaco, Texas in 1993 and Maricopa, Arizona in 1992. Yields of cotton treated with either insecticide were not significantly reduced by season long larval infestations compared to untreated checks. Mixture and alternate application of insecticides did not increase control of whitefly compared to each insecticide alone in the LRGV. Vial bioassays with bifenthrin and endosulfan in treated and untreated plots were conducted during the season and LC(50) values were variable. When adults of Eretmocerus sp. nr. Californicus Howard were exposed to 48 hr residues of endosulfan at 0.56 and 1.12 kg (AI)/ha survival was 35% and 20%, respectively. Adults of Encarcia pergandiella Howard were more susceptible to endosulfan than E. sp. nr. at the same rates. Adult or immature predator (i.e. Collops sp., spiders, Scymnus sp., Orius spp.; Geocoris sp., Chrysoperla spp., Hippodamia convergens Guerin-meneville) populations were reduced 32 and 53% after the first and 2(nd) application of endosulfan at 0.56 kg (AI)/ha in the field, respectively. Both insecticides were effective against B. tabaci at Weslaco and Maricopa in field plots based on control of adults and immatures.