INTERACTIONS OF THE WHITEFLY PREDATOR DELPHASTUS-PUSILLUS (COLEOPTERA, COCCINELLIDAE) WITH PARASITIZED SWEET-POTATO WHITEFLY (HOMOPTERA, ALEYRODIDAE)

Delphastus pusillus (LeConte), an indigenous coccinellid predator of w hiteflies, including sweetpotato whitefly, Bemisia tabaci (Gennadius), feeds on all stages of whiteflies. In laboratory tests, fourth-instar and adult female D. pusillus exhibited a marked tendency to avoid fou rth-instar B. tabaci parasitized by the aphelinid endoparasitoids Enca rsia transvena (Timberlake) and Eretmocerus sp. nr. californicus Howar d in favor of unparasitized whiteflies. The age of the parasitoid with in the whitefly influenced the extent of the avoidance. Whiteflies wit h first-instar parasitoids were not avoided, but those containing thir d instars and pupal parasitoids were significantly avoided. The presum ed causes of the avoidance include parasitism-induced hardening of the whitefly cuticle and introduction of air into the whitefly around mat uring parasitoids. D. pusillus and parasitoids tend to attack differen t stages of the whitefly. This attribute increases temporal separation , enhancing the options for the use of D. pusillus in pest management programs in conjunction with parasitoids.