Effects of Def and Dropp alone and in combination with two insecticides, Karate (a pyrethroid) and Guthion (an organophosphate) on silverleaf whitefly, Bemisia argentifolii Bellows & Perring were determined in 2001. The defoliants, Def and Dropp, and their combinations with Guthion and Karate significantly affected the infection and survival of both silverleaf whiteflies and their parasitoids, Encarsia spp. and Eretmocerus spp, although the effects varied greatly among the treatments. Karate had no significant effects on silverleaf whitefly and its parasitoids. Combining defoliants and insecticides increased the effectiveness on whiteflies and parasitoids on cotton.