RESPONSE OF ADULT PARASITOIDS OF BEMISIA-TABACI (HOM, ALEYRODIDAE) TOLEAF RESIDUES OF SELECTED COTTON INSECTICIDES

The contact toxicity of eight insecticides to adults of four parasitoi ds of the sweetpotato whitefly Bemisia tabaci was evaluated in the lab oratory. Two common Texas species, Eretmocerus sp. and Encarsia pergan diella Howard, and two exotic species, Eretmocerus mundus Mercet from Spain and Encarsia formosa Gahan from Greece were tested. Insecticides , applied as sprays to greenhouse-grown cotton plants at recommended r ates were amitraz (Ovasyn(R)), azinphosmethyl (Guthion(R)), bifenthrin (Capture(R)), buprofezin (Applaud(R)), cypermethrin (Ammo(R)), methyl parathion and thiodicarb (Larvin(R)), with a water control. Parasitoi d adults were confined on discs cut from leaves (1) sprayed the same d ay and (2) sprayed two days previously. Survival in both treatments wa s measured two and four days following exposure. Significant differenc es in toxicity were detected among the insecticides. Buprofezin was no t toxic to any of the four parasitoids. When caged on leaves sprayed t wo days previously, only amitraz of the remaining compounds allowed si gnificant general parasitoid survival after two days. E. mundus exhibi ted the greatest overall tolerance to insecticides, with 40 % or more surviving 48 hr after confinement on leaves sprayed with amitraz, thio dicarb and cypermethrin. Survival was generally much reduced after 96 hr. In a separate test, fresh residues of endosulfan (Thiodan(R)) were highly toxic at the two rates tested, but two day old residues at the lower rate allowed 76.7 % survival of E. mundus and 35 % survival of E. pergandiella after 48 hrs.