Cotton defoliation is an important management practice associated with high-yielding, high-quality cotton. The impacts of two commonly-used defoliants (tribufos and thidiazuron) individually and in combination with two commonly-used insecticides (lambda-cyhalothrin and azinphosmethyl) on the sweetpotato whitefly, Bemisia tabaci Gennadius biotype B (= silverleaf whitefly, Bemisia argentifolii Bellows & Perring) and its parasitoids were determined in field studies in the Lower Rio Grande Valley of Texas. The two defoliants and their combinations with azinphosmethyl and lambda-cyhalothrin significantly affected the occurrence and survival of sweetpotato whiteflies and their parasitoids, Encarsia spp. and Eretmocerus spp., although the effects varied among the treatment combinations. Lambda-cyhalothrin alone had no significant effects on sweetpotato whitefly and its parasitoids. Combining defoliants and insecticides appears to be a potential management tool for whiteflies on cotton.