INTERACTIONS OF SEVERAL INSECTICIDES AND A CARABID PREDATOR (BEMBIDION LAMPROS (HRBST.)) AND THEIR EFFECTS ON HYLEMYA BRASSICAE (BOUCHÉ)

Abstract

Bembidion lampros (Hrbst.) is an important egg predator of the cabbage maggot, Hylemya brassicae (Bouché), but populations may be seriously reduced by application of broad spectrum insecticides for the control of other pests. The efficiency of B. lampros as a predator of H. brassicae eggs and the effects of three insecticides on the beetle were determined in experimental plots of Brussels sprouts. In untreated plots, B. lampros ate 45% of the H. brassicae eggs. In plots treated with methomyl, Bacillus thuringiensis (Dipel), and chlorfenvinphos, egg numbers were reduced 35, 44 and 66%, respectively. One subsurface application of chlorfenvinphos granules, early in the season, prevented damage by the cabbage maggot and was not toxic to the beetle. Foliar applications of methomyl significantly reduced the number of B. lampros. In laboratory tests with methomyl at 0.1, 0.05, 0.025 and 0.0125%, the mortality of B. lampros was 100, 70, 40 and 0%, respectively. Dipel sprays at 0.1 or 0.5% and chlorfenvinphos in the soil at 10 or 40 ppm caused only slight mortality.