Integrating pesticide effects with inundative biological control: interpretation of pesticide toxicity curves for Anaphes iole in strawberries

We examined pesticide residue effects on the egg parasitoid Anaphes iole Gi rault (Hymenoptera: Mymaridae), an inundative biological control agent for Lygus hesperus Knight (Heteroptera: Miridae) in strawberries (Fragaria x an anassa Duchesne). Our objectives were to identify compatible pesticides, de termine appropriate parasitoid release timings for minimizing harmful effec ts, and develop an approach for interpreting pesticide toxicity curves. Six insecticides, 2 acaricides and 6 fungicides were tested, and survivorship of adult A. iole exposed to foliar residues for 48 h, at 4-6 different time s after pesticide application, was examined. A logistic function was develo ped for incorporating control mortality at each test date. Values for LT50 (Lethal Time for 50% mortality) and mortalities on day 1 (initial mortality ) and day 13 (estimated maximum time parasitoid releases can be delayed und er extreme summer conditions) were estimated. In the study, insecticide res idues proved to be the most toxic, followed by those from acaricides while most fungicides were least toxic. Among insecticides, fenpropathrin, bifent hrin and carbaryl caused the greatest mortality (estimated mortality on day 13 > 75%). Residues of naled resulted in the least mortality (LT50 = 3.2 d ays) followed by methomyl (LT50 = 8.3 days) and malathion (LT50 = 13.2 days ). Estimated mortality = 12.3% on day 13 for the acaricide propargite and < 1% for abamectin. For the fungicides benomyl, captan, myclobutanil and thi ram, estimated mortality on day 1 was < 1%, and for iprodione it was < 6%, indicating compatibility with A. iole releases. For sulfur, LT50 = 0, but t he mortality decay curve was relatively flat (estimated mortality on day 13 = 13.6%). These results suggest possibilities for integrating A. iole rele ases with certain pesticide programs by appropriate timing of pesticide app lications to minimize negative impacts.