Symptoms
Small irregular holes in leaves from larval feeding. Window-pane feeding pattern on leaf undersides. Small pale green caterpillars visible. Severe defoliation in hot dry weather.
Prevention
Use fine mesh netting over seedbeds. Rotate crops with non-brassica species. Use pheromone traps for early detection. Intercrop with aromatic plants. Remove crop debris promptly after harvest.
Treatment
Organic
Apply Bacillus thuringiensis (Bt var. kurstaki) at early instar stage. Release Cotesia plutellae parasitoids. Use spinosad sprays. Avoid broad-spectrum insecticides to preserve natural enemies.
Chemical (last resort)
Apply emamectin benzoate or chlorfenapyr. DBM has developed resistance to many insecticides — rotate chemical groups every 2 applications. Never use pyrethroids alone.
Affects 3 crops
Sources
MARDI Vegetable Pest Guide; DOA IPM Manual