Effects of imidacloprid on development, mobility, and survival of first instars of Diaprepes abbreviatus (Coleoptera: Curculionidae)
1997
Quintela, E.D. | McCoy, C.W.
The effect of imidacloprid on mortality and ecdysis of 1st instars of Diaprepes abbreviatus L. was determined using contact and oral exposure bioassays. The effect of contact exposure to imidacloprid on 1st-instar mobility was determined with and without a soil substrate. Greenhouse 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 at doses of 212.5 ppm, imidacloprid reduced feeding, which contributed to slower larval development and reduced ecdysis. Imidacloprid also affected larval mobility and development by contact exposure at doses >100 ppm. Larval mobility was impaired significantly in soil treated with imidacloprid at doses >6 micrograms/g of soil. In moistened soil, larval movement was significantly impaired at 6 micrograms/g of soil. Mortality caused by imidacloprid was slow for either mode of entry 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 chemical, larvae were able to recover. When imidacloprid was applied as a soil drench to container-grown citrus trees at 200 ppm, no larvae survived in the soil, suggesting death from starvation before reaching plant roots or death after feeding, on roots containing imidacloprid.
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