The imported cabbageworm adult is one of the most common butterflies in the Northeast. The velvety-green caterpillar of this butterfly feeds on the leaves of cabbage, cauliflower, broccoli, Brussels sprouts, turnips, radishes, kale, lettuce and weeds of the mustard family. The imported cabbageworm is one of the most damaging and destructive enemies of these plants. The caterpillars chew irregular holes in the leaves and usually eat their way into cabbage heads from the bottom. The fecal pellets of the caterpillars will also stain cauliflower. These caterpillars can be controlled with microbial insecticides based on strains of Bacillus thuringiensis effective against caterpillars, or row covers can be used to keep the adults from laying eggs on plants in the garden.

Description:

The first sign of the imported cabbageworm is the 40 mm (1.5 inch) long white butterfly, first seen in early spring. The butterfly has black-tipped front wings with one or two black dots and one black dot on each hind wing. The females fly during daylight hours looking for suitable plants on which to lay their yellowish, elongated eggs, singly, on the underside of leaves. The velvety-green caterpillar has a faint yellow stripe down its back and a row of faint yellow spots on each side. When fully grown, the caterpillar is slightly more than 25 mm (1 inch) long.

The eggs laid by the butterfly on the underside of leaves hatch in five to seven days. There can be as many as three generations of the imported cabbageworm in the Northeast. Adults may be seen almost anytime during the summer.

The pupa, or chrysalis, of the imported cabbageworm is green or tan, 20 mm (3/4 inch) long, and attached to the plant or other surface by silken threads. The imported cabbageworm overwinters as a pupa, attached to any convenient stem, branch, fencepost, or other hard surface in the area.