Selectivity of insecticides to Encarsia pergandiella (Hymenoptera: Aphelinidae), an endoparasitoid of Bemisia argentifolii (Hemiptera: Aleyrodidae)

Encarsia pergandiella Howard is the most abundant parasitoid of silverleaf whitefly, Bemisia argentifolii Bellows & Perring, in south Florida vegetable fields and can contribute significantly to natural biological control of this and other whitefly species. However, quality standards, costs, and risks in commercial tomato production are high, resulting in frequent recourse to chemical control. Therefore, successful utilization of biological control could depend on compatibility of the parasitoid with selective insecticides. We tested a wide range of potentially selective insecticides, represented by a mineral oil, an insecticidal soap, a neem seed extract and synthetic and natural sugar esters, against eggs, first and third instar larvae, pupae and adults, using a pyrethroid, Capture" (20 g bifenthrin/1 EC), for comparison. Capture" residues on nymphs exposed to adult parasitoids reduced parasitization more than other materials tested, and were most toxic to all parasitoid stages. Mineral oil caused high mortality to immature parasitoids, and residues reduced parasitization of £. pergandiella. However, oil residues were much less toxic to adults if applied as a spray to leaf surfaces than as a dip to a leaf and especially glass surfaces. In contrast, the toxicity of Capture" was high regardless of bioassay method. Neem extract, insecticidal soap and both sugar esters tested had little or no effect on E. pergandiella. These latter materials could be considered selective in respect to E. pergandiella and might be used to suppress B. argentifolii without decimating parasitoid populations.