Lettuce: Cabbage Looper

Problem
Leaves have round or irregular holes. Green worms up to 1½ inches long, with light stripes down their backs, feed on the leaves or heads. Masses of green or brown pellets may be found between the leaves.

Analysis
(Trichoplusia ni)

Several worms attack lettuce, the most damaging of which is the cabbage looper. The looper attacks all varieties of lettuce, as well as members of the cabbage family. Adults lay eggs throughout the growing season. The brownish cabbage looper moth lays pale green eggs on the upper sides of the leaves in the evening. The worms eat lettuce leaves and heads. Their greenish brown excrement makes the plants unappetizing. Worms may be present from early spring until late fall. In the South, they may be present all year. Worms spend the winter as pupae attached to a plant or nearby object.

Solution
Control cabbage loopers with an insecticide containing carbaryl, pyrethrins, or diazinon, or the biological insecticide Bacillus thuringiensis (Bt). Bt is effective only while the caterpillars are small. Repeat treatments at weekly intervals if the plants become reinfested. Clean all plant debris from the garden to reduce the number of overwintering pupae.