These destructive worms are either the cabbage looper (Trichoplusia ni) or the imported cabbageworm (Pieris rapae). Both worms attack all members of the cabbage family, as well as lettuce. Adults lay eggs throughout the growing season. Adults of the imported cabbageworm attach yellow, bullet-shaped eggs to the undersides of leaves. These white butterflies are frequently seen around cabbage plants in the daytime. The brownish cabbage looper moth lays pale green eggs on the upper surfaces of leaves in the evening. 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.
Control cabbageworms with an insecticide containing carbaryl, diazinon, or pyrethrins, or an insecticidal soap. Spray as soon as damage is seen. Cabbageworms can also be killed with the biological insecticide Bacillus thuringiensis (Bt), while they are small. Repeat treatments weekly as long as worms are found, but stop 3 days before harvest. Remove plant debris after harvest to destroy the pupae.
Plant Care for Cabbage Family