EFFECTS OF IMIDACLOPRID ON DEVELOPMENT, MOBILITY, AND SURVIVAL OF FIRST INSTARS OF DIAPREPES-ABBREVIATUS (COLEOPTERA, CURCULIONIDAE)

The effect of imidacloprid on mortality and ecdysis of Ist instars of Diaprepes abbreviatus L. was determined using contact and oral exposur e bioassays. The effect of contact exposure to imidacloprid on Ist-ins tar mobility was :as determined with and without a soil substrate. Gre enhouse studies were conducted to determine possible systemic effects of different rates of imidacloprid applied as a soil drench on larval mortality and on root protection of container-grown citrus seedlings. When larvae were fed treated carrot or artificial diet st doses of gre ater than or equal to 12.5 ppm, imidacloprid reduced feeding, which co ntributed to slower larval development and reduced ecdysis. Imidaclopr id also affected larval mobility and development by contact exposure a t doses >100 ppm. Larval mobility was impaired significantly in soil t reated with imidacloprid at doses >6 mu g/g of soil. In moistened soil , larval movement was significantly impaired at 6 mu g/g of soil. Mort ality caused by imidacloprid was slow for either mode of en but was 6 times faster by oral than by contact exposure. When exposure to doses of imidacloprid was followed by periods without exposure to the chemic al, larvae were able to recover When imidacloprid was applied as a soi l drench to container-grown citrus trees at 200 ppm, no larvae survive d ill the soil, suggesting death from starvation before reaching plant roots or death after feeding, on roots containing imidacloprid.