Because the imported cabbageworm caterpillar is the same velvety green color as cabbage leaves, it can be hard to see. However, its chewing damage will be obvious. One caterpillar can eat several square inches of foliage a day. Also, if you see one, there are bound to be more. - Clemson University USDA Cooperative Extension Slide Series, www.insectimages.org

This white butterfly with a black spot on the wings is the adult imported cabbageworm; when you see it hovering around the garden, look out for its green caterpillars. - David Adams, University of Georgia, www.insectimages.org

The pupae of cabbageworms linger in and around the garden in winter to give rise to a whole generation of pests next year. - Whitney Cranshaw, Colorado State University, www.insectimages.org

The southern cabbageworm looks like the cross-striped cabbageworm, only it has long yellow stripes down its back. - Alton Sparks Jr., University of Georgia, www.insectimages.org

The cross-striped cabbageworm is recognizable by the stripes across its back; it walks like an inchworm. - Clemson University USDA Cooperative Extension Slide Series, www.insectimages.org

These caterpillars chew holes in the leaves of broccoli, cabbage, collards, kale, Brussels sprouts, mustard, and other related crops. When the cabbageworms first hatch, they are very tiny, but as they grow to 1 to 2 inches long, they quickly damage plants and deposit messy excrement on the leaves.

Leaves can be so badly chewed that they are worthless. Recovery depends on how bad the infestation is and whether there is much new growth. Mustard, kale, and collards make quick new growth from the center of the plant and will be fine as soon as the new leaves appear. The hardest to recover are seriously chewed brussels sprouts, and cabbage and broccoli heads.

Cabbageworms are easy to prevent with sprays of Bt (Bacillus thuringiensis). Use this to guard precious heads of cabbage and other cole crops. If already present, spray with pyrethrin, neem, or insecticidal soap for a quick kill and then guard against further infestation with sprays of Bt. Or, if you have just a few plants, you can hand pick the caterpillars from your plants.

The imported cabbageworm butterfly is easy to spot in your garden. You've probably seen the white butterfly and thought, "Oh, how nice, a butterfly." See the picture on the right. One way to keep the butteflies and moths that give rise to these caterpillars off your plants is to cover the plants with floating row covers in the spring. They are a physical barrier that keeps the insects from  being able to lay eggs on the leaves.

Eggs? Yes, caterpillars hatch from eggs laid by butterflies and moths.

When spraying, be sure to get the undersides of the leaves because that is where they often rest. Also, be sure that your spray drips down into the folds of cabbage heads and tight places in all the plants.