Survival and behavior of Plutella xylostella larvae on cabbages with leaf waxes altered by treatment with Sethyl dipropylthiocarbamate

Cabbages (Brassica oleracea L.) treated with S-ethyl dipropylthiocarbamate (EPTC) herbicide had reduced amounts of leaf surface waxes (40.6~o of controls) and reduced densities of leaf surface wax crystallites (20.8~o of controls). Leaf waxes of EPTC-treated plants chemically and morphologically resembled leaf waxes of genetically glossy cabbages resistant to the diamondback moth Plutella xylostella (L.) (Lepidoptera: Plutellidae). Survival of larvae was significantly reduced on EPTC-treated cabbage plants in three out of four experiments (62.0-15.3 ~o of survival on controls). P. xylostella neonates also moved more rapidly on EPTC-treated plants than on untreated controls (1.84 + 0.16 cm/min on controls vs. 3.94 + 0.24 cm/min on treated plants; P = 0.0001). These results support the hypotheses that reduction in leaf waxes is the basis of resistance to P. xylostelIa in genetically glossy plants and that reduced acceptance by larvae is associated with this resistance. Modification of leaf surface waxes with EPTC or similar compounds may have potential as an economic control for P. xylostella in Brassica crops.