ACUTE TOXICITY AND TIME-DEPENDENT MORTALITY OF CHLORFLUAZURON AND TRIFLUMURON AGAINST SECOND-INSTAR PIERIS BRASSICAE (LEPIDOPTERA: PIERIDAE)

Abstract

The cabbage butterfly, Pieris brassicae (Linnaeus, 1758) (Lepidoptera: Pieridae), is an important defoliating pest of cruciferous vegetables. Laboratory bioassays were conducted during 2012–2013 to evaluate the acute toxicity of two insect growth regulators, chlorfluazuron and triflumuron, against second-instar larvae. A leaf-dip method was used with concentrations of 1, 3, 5 and 7%, and water-treated leaves served as the control. Forty larvae were exposed to each concentration, and mortality was recorded after 24, 48, 72, 96 and 120 h. Both compounds produced concentration- and time-dependent mortality. Chlorfluazuron mortality after 120 h was 73, 95, 98 and 100% at 1, 3, 5 and 7%, respectively. Triflumuron mortality after 120 h was 63, 93, 98 and 100% at the same concentrations. No mortality occurred in the control. The results show that both insect growth regulators were highly active against second-instar P. brassicae under the laboratory conditions used in this study, with mortality increasing as exposure duration and concentration increased..