Lethal and sublethal effects of imidacloprid on apple maggot fly, Rhagoletis pomonella Walsh (Dipt., Tephritidae)

Imidacloprid technical ingredient was tested in the laboratory to determine ingestion/contact or contact alone toxicity over a 5-day period to apple maggot flies, Rhagoleta pomonella (Walsh). Formulated imidacloprid was also tested in the field against R. pomonella flies for residual efficacy over a 7-day period. In the laboratory tests, imidacloprid showed high lethal and sublethal effects. It was 10-12 times more toxic and acted more rapidly by oral ingestion than by surface contact. Affected flies were observed to cease feeding and then regurgitate. Mortality stabilized 4 days after treatment. Compared with control flies, females exposed to imidacloprid showed reduced Fecundity regardless of whether exposure was by oral or surface contact. In field experiments, spray applications of imidacloprid to foliage at the manufacturer's recommended rate resulted in no significant mortality of flies, either among flies released immediately after treatment or 24 h later. Imidacloprid 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.