LETHAL AND SUBLETHAL EFFECTS OF IMIDACLOPRID ON APPLE MAGGOT FLY, RHAGOLETIS-POMONELLA WALSH (DIPT., TEPHRITIDAE)

Imidacloprid technical ingredient was tested in the laboratory to dete rmine ingestion/contact or contact alone toxicity over a 5-day period to apple maggot flies, Rhagoleta pomonella (Walsh). Formulated imidacl oprid was also tested in the field against R. pomonella flies for resi dual efficacy over a 7-day period. In the laboratory tests, imidaclopr id showed high lethal and sublethal effects. It was 10-12 times more t oxic and acted more rapidly by oral ingestion than by surface contact. Affected flies were observed to cease feeding and then regurgitate. M ortality stabilized 4 days after treatment. Compared with control flie s, females exposed to imidacloprid showed reduced Fecundity regardless of whether exposure was by oral or surface contact. In field experime nts, spray applications of imidacloprid to foliage at the manufacturer 's recommended rate resulted in no significant mortality of flies, eit her among flies released immediately after treatment or 24 h later. Im idacloprid residue on tree leaves reduced the reproductive ability of flies released immediately after treatment, but the effect was minimal . The potential use of imidacloprid as a toxicant on pesticide-treated spheres is discussed.