A serious pest of all members of the cabbage family, these destructive caterpillars are green with a faint yellow stripe down the back and along each side.

They attack cabbages, broccoli, nasturtiums, stocks, wallflowers and watercress. They feed from under the leaf, starting on the outer leaves.

They are small, no more than 30mm long, and infestation is worst in late summer and early autumn. The yellowish butterflies have three or four black spots on the tips of the wings and a wingspan of nearly 50mm.

Control:
Spray with carbaryl or with Bacillus thuringiensis (a disease that affects only caterpillars) or use a contact powder.