Impact of bifenthrin on honeybees and Culex quinquefasciatus.

The impact of bifenthrin on honeybees, Apis mellifera (Hymenoptera: Apidae) was evaluated in both laboratory and semifield assays. Ten serial dilutions of bifenthrin and an acetone control using the bottle bioassay protocol were used in the laboratory to determine killing time after 15-, 30-, and 60-min honeybee exposure. Both dose and exposure time significantly affected honeybee mortality (df = 6, F = 10.9, P < 0.05). Application dose of 35 microg/ml resulted in 100% bee mortality at all time intervals. Bifenthrin was applied at 9.7 ml/liter, 19.5 ml/liter, and 29.5 ml/liter of water to common landscape vegetation, Melampodium paludosum Melanie (show star) and Duranta erecta L. (golden dewdrop); a water control was also used. Bee mortality was significantly higher (P < 0.05, df = 2, F = 20.8) at 29.5 ml/liter compared to the mortality at 19.5-ml/liter and 9.7-ml/liter application rates after 24-h exposure to the treated vegetation. Mortality of Culex quinquefasciatus exposed to treated vegetation was significantly (P < 0.05, df = 10, F = 114) different by week and by application rate.