Response of Bemisia argentifolii (Homoptera: Aleyrodidae) to imidacloprid under greenhouse, field, and laboratory conditions

The systemic insecticide imidacloprid has been used successfully to manage Bemisia argentifolii Bellows & Pet-ring and whitefly-borne geminivirus on tomato in south Florida and elsewhere. We evaluated plant and whitefly responses to imidacloprid in greenhouse grown tomato, Lycopersicon esculentum Miller, transplants and field-grown fresh market staked tomato. Seedlings in transplant trays treated with 1 or 2 mg (AI) per plant applied as a drench were protected from egg deposition for up to 6 wk of exposure to a greenhouse colony of whiteflies. In the field, either 280 or 560 g (AI)/ha of imidacloprid applied to the soil at transplanting provided protection from all whitefly stages and was better than or equal to protection obtained with weekly sprays of organophosphate/pyrethroid insecticide mixtures for up to 9 wk, Movement of geminivirus infection vectored by whitefly adults was suppressed in small plots, indicating that imidacloprid acted rapidly on adults. Treated tomato or eggplant, Solanum melongena L. 'Black Beauty', functioned as trap crops by reducing whitefly numbers on adjacent untreated tomato. High application rates and persistence of imidacloprid have combined to increase the likelihood of insecticide resistance and to necessitate the development of an easily reproducible bioassay to facilitate monitoring. A leaf-dip bioassay indicated that the LC50 for 10-d-old whitefly nymphs to imidacloprid was 6.1 mg (AI)/liter and the LC90 was 32.6 mg (AI)/liter. These results could serve as a baseline for whitefly susceptibility in south Florida, given the lack of any previous exposure to imidacloprid of the-tested population.