Insecticide toxicity was assayed using a leaf-dipping bioassay as described
previously [25]. Leaf discs (6.5 cm diameter) were cut from
young cabbage plants (Brassica oleracea) grown without exposure to insecticides
in our greenhouse. The insecticides were serially diluted to
five to seven required concentrations with distilled water containing
0.1% Triton X-100. Four leaf discs were grouped together and were
dipped in insecticide solutions of different concentrations for 10 s.