Effects of two insect growth regulators and a neonicotinoid on various life stages of <Emphasis Type="Italic">Aphytis melinus</Emphasis> (Hymenoptera: Aphelinidae)

The effect of two insect growth regulators and a neonicotinoid insecticide were tested on immature stages and adults of the parasitoid Aphtyis melinus DeBach (Hymenoptera: Aphelinidae), a key natural enemy of California red scale, Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae), in California. No significant effects of the insect growth regulators on survival or development to the adult stage were found when the parasitoid was treated at any of the egg, larval, or pupal stages. The broad-spectrum neonicotinoid acetamiprid also showed no significant effect on the development of A. melinus to the pupal stage, probably because immature stages of this ectoparasitoid are protected under the cover of its armored scale host. However, 48 h exposure of adults to acetamiprid residues following emergence resulted in high levels of wasp mortality. Aphytis melinus adults treated with either of the two insect growth regulators as larvae survived 48 h exposure to pesticide residues as adults and showed levels of fecundity comparable with control insects. We conclude that the two insect growth regulators are compatible with augmentative releases of A. melinus but that treatments of acetamiprid should be avoided in situations where biological control by this parasitoid is important.