Pacific Pests, Pathogens and Weeds

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Summary

• Worldwide distribution. Members of the cabbage (brassica) family, e.g., head cabbage, Chinese cabbage, radish, cauliflower and broccoli; Amaranthus and watercress. An important pest.
• Eggs, yellow, small, laid singly. Young larvae mine leaves; larger ones leave waxy windows and holes. If touched, larger ones wiggle backwards, and fall down on silk threads.
• Natural enemies: wasp parasitoids, especially Cotesia (see Fact Sheet no. 287) and Diadegma (see Fact Sheet no. 285).
• Cultural control: inspect nurseries and crops regularly; remove larvae; use trap crops, e.g., mustards or Chinese cabbage (Bok Choy), but destroy trap crop before eggs hatch.
• Chemical control: in household plots, PDPs (chillies, neem, derris, pyrethrum to safeguard natural enemies); in commercial plots, grow under nets; use Bt (Bacillus thuringiensis) sprays against caterpillars when young. Avoid pyrethroids and organophosphates.