Effect of pesticides on Colpoclypeus florus (Hymenoptera : Eulophidae) andTrichogramma platneri (Hymenoptera : Trichogrammatidae), parasitoids of leafrollers in Washington

Pesticides were evaluated for their effect on two parasitoid species, Colpo clypeus florus and Trichogramma platneri, that are potential biological con trol agents of leafrollers in apple orchards. Organophosphate and carbamate insecticides were highly toxic to both parasitoids in topical applications , but foliar residues of some products were nontoxic after 7 d. At reduced rates, topically applied pyrethroids were low in toxicity to C. florus were highly toxic to T platneri, and foliar residues were nontoxic after about 7 d. Imidacloprid and abamectin were highly toxic when applied topically to both parasitoids but were not toxic as 1-d-old residues. Insect growth reg ulators did not cause mortality either as topical applications or residues; however, diflubenzuron caused severe sublethal effects, completely blockin g the production of C. florus offspring. Biorational pesticides, such as so ap, oil, and B. thuringiensis products, caused no toxicity to C. florus but had a direct impact on T platneri as topical applications through physical immobilization, The potential to integrate different pesticides with biolo gical control of leafrollers and the need for a step-wise approach to evalu ate the impact of pesticides against natural enemies is discussed.