Einat Zchori-Fein, 
Richard T. Roush, 
John P. Sanderson

The compatibility of abamectin with Encarsia formosa Gahan (Hymenoptera: Aphelinidae) as a part of integrated pest management of the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae), was assessed in a series of laboratory and greenhouse experiments. In laboratory experiments using commercially formulated abamectin at the concentration recommended for greenhouse use, mortality of the adult parasitoids ranged from 100%, when exposed to 2-h-old abamectin residues on bean plants (Phaseolus vulgaris) in the presence of whitefly larvae, to 0% when exposed to 24-h-old residues without whitefly larvae. More than 50% of the E. formosa successfully eclosed from parasitized whitefly pupae on bean leaves dipped in formulated abamectin. In the greenhouse experiment, the combined treatment of abamectin and E. formosa maintained significantly lower densities of whiteflies on poinsettia, Euphorbia pulcherrima (Willdenow), throughout the season with fewer abamectin applications than did abamectin alone. Moreover, the percentage of parasitism did not differ significantly among plants treated with and without abamectin. Abamectin might be used to reduce whitefly numbers on poinsettia without eliminating the parasitoid population when releases of E. formosa are not satisfactory. A possible explanation for the partial selectivity of abamectin to E. formosa is discussed.