MANAGING LEPIDOPTERAN PESTS IN CABBAGE WITH HERBICIDE-INDUCED RESISTANCE, IN COMBINATION WITH A PYRETHROID INSECTICIDE

S-ethyldipropylthiocarbamate (EPTC) applied as a soil treatment or ove r-the-top spray on cabbage plants (Brassica oleracea L.) caused the le aves to turn 'glossy' for as long as 30 days. EPTC-induced glossy plan ts were damaged significantly less than untreated plants by diamondbac k moth, Plutella xylostella (L.), imported cabbage worm, Pieris rapae (L.), and cabbage looper, Trichoplusia ni (Hbn.). Reductions in damage were equivalent to those obtained from treatment with permethrin. Whe n used in combination with permethrin, EPTC provided additive control of damage by these pests. Our calculations show EPTC-induced resistanc e to be cost-effective. This use of EPTC has several limitations, howe ver. Younger plants (< 9 leaves) were killed or injured by the herbici de. The growth of older plants was not affected, but plants did not be come glossy for ca. 10 days after they were treated with EPTC. The cro p must be protected with insecticides until the plants are mature enou gh to treat with EPTC, and until treated plants become glossy. In addi tion, since the glossy trait is only effective against first instar la rvae, populations of later instars on glossy plants must be reduced wi th an application of insecticide. Finally, EPTC formulations are water -soluble and can be washed away from the plants by heavy rains and irr igation, which may make this use of EPTC impractical in some situation s. Where its use is practical, and the indicated precautions are taken , EPTC-induced resistance could reduce dependence on chemical insectic ides and reduce selection for insecticide resistance in diamondback mo th.