Pacific Pests, Pathogens and Weeds

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Summary

• Worldwide distribution. Common parasitising diamondback moth (DBM) in the hot lowland tropics and sub-tropics. Female lays 200 eggs, one in each young DBM caterpillars.
• Cotesia larvae eat DBM caterpillar from inside, emerges from the caterpillar and makes a cocoon on the brassica leaf. Look for white, oval pupa. The adult wasp (2-3.5 mm long) hatches after about 7 days and feeds on nectar.
• Cotesia cannot prevent damage by DBM alone. IPM programs avoid pyrethroids and organophosphates (these kill Cotesia and predators) and recommend use of Bt (Bacillus thuringiensis).
• Monitor and only use Bt when needed; rotate this with other insecticides to prevent resistance to Bt developing.