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

Delphastus pusillus (LeConte), an indigenous coccinellid predator of whiteflies, 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 fourth-instar B. tabaci parasitized by the aphelinid endoparasitoids Encarsia transvena (Timberlake) and Eretmocerus sp. nr. californicus Howard in favor of unparasitized whiteflies. The age of the parasitoid within the whitefly influenced the extent of the avoidance. Whiteflies with first-instar parasitoids were not avoided, but those containing third instars and pupal parasitoids were significantly avoided. The presumed causes of the avoidance include parasitism-induced hardening of the whitefly cuticle and introduction of air into the whitefly around maturing parasitoids. D. pusillus and parasitoids tend to attack different 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.