SUSCEPTIBILITY OF HOUSE-FLIES (DIPTERA, MUSCIDAE) AND 5 PUPAL PARASITOIDS (HYMENOPTERA, PTEROMALIDAE) TO ABAMECTIN AND 7 COMMERCIAL INSECTICIDES

Assays of five commercial insecticides applied as residual sprays at l abel rates to plywood indicated the most toxic insecticide overall for pteromalid parasitoids of house flies, Musca domestica L., was Atroba n (permethrin), followed by Ciodrin (crotoxyphos), Rabon (tetrachlorvi nphos), Ectrin (fenvalerate), and Cygon (dimethoate). Insecticide-susc eptible house flies were susceptible to all five insecticides (mortali ty, 62-100%). Flies that were recently colonized from populations on d airy farms in New York were susceptible only to Rabon. Urolepsis rufip es (Ashmead) was the most susceptible parasitoid species overall to th ese insecticides, followed by Muscidifurax raptor Girault & Sanders, N asonia vitripennis Walker, Pachycrepoideus vindemmiae (Rondani), and S palangia cameroni Perkins. Compared with susceptible flies, newly colo nized flies showed moderate resistance to avermectin B1a (abamectin). Abamectin was more toxic to all of the parasitoids except N. vitripenn is and S. cameroni than to newly colonized house flies when exposed fo r 90 min to plywood boards treated with 0.001-0.1% abamectin. Space sp rays with Vapona (dichlorvos) killed all of the parasitoids and suscep tible flies and 64% of the newly colonized flies when insects were pla ced directly in the path of the spray; mortality was substantially low er among flies and parasitoids protected under 5 cm of wheat straw. Sp ace sprays with Pyrenone (pyrethrins) killed > 86% of all insects expo sed to the spray path except for the newly colonized flies (1% mortali ty); mortality of insects protected under straw was low (< 12%) except for S. cameroni (76%). Because responses of the five parasitoids to t he different insecticides varied considerably, general conclusions abo ut parasitoid susceptibility to active ingredients, insecticide class, or method of application were not possible.