Cole Crop Caterpillars, Vol. 9, No. 28
Order: Lepidoptera
“Cole crops” is a colloquial name for “crucifers.”. Crucifers is a somewhat archaic name for “Brassicas.” Brassica crops include things like cabbage, broccoli, turnips, bok choy, and other vegetables in the genus Brassica. Despite their wide variability in appearance and taste, most vegetable brassica belong to one of two species. For example, cabbage, broccoli, cauliflower, collards, and kale are all the same species, Brassica oleracea. Turnips, mustard, Napa cabbage, bok choy, and canola are all B. rapa.
Cole crops are attacked by a complex of caterpillar pests that, like their host plants, thrive in the cooler temperatures of fall, winter, and spring. Gardeners who enjoy growing and eating cole crops need to be able to recognize these various caterpillars and know how to control them.
Cabbage loopers are easy to identify by the way they move. They have fewer prolegs than most caterpillars, forcing them to crawl in a looping or inchworm-like manner. Fully mature caterpillars can be up to 1.5 inches.
Diamondback moth caterpillars are less than ½ inch long when fully mature. The dark-colored moths are only about ¼ inch, and when viewed from above have a tan streak down the center of the back that seems to be made up of a series of overlapping diamond shapes. Despite their small size, this is the most economically important pest of brassica crops worldwide. Diamondback moths are infamous for their ability to quickly develop resistance to new insecticides.
Imported Cabbageworm is one of the few butterflies whose caterpillars are significant pests. The butterflies are mostly white with black wing tips. Unlike most moths, butterflies fly and lay eggs during the day. The caterpillars are uniformly green and are covered with many fine hairs, giving them a velvety texture, and making them easy to identify.
Cross-striped cabbageworms also easy to identify; they have gray and black strips alternating across their backs and are about ¾ inches long when mature. This is the least common pest of this foursome, but they cause a lot of damage when they occur in home gardens.
If you have caterpillars eating your cole crops, it does not really matter what species they are. No one wants to eat leaves with holes chewed in them or to have to spend extra time removing caterpillars, and their fecal pellets, from harvested plants.
Control: Check fall/winter vegetables regularly and treat at the first signs of insect feeding. Spinosad works well on all caterpillar pests, including hard to kill diamondback moths, and also controls yellowmargined leaf beetles and vegetable weevils, which are important pests of turnips, bok choy and other brassica. Products containing the active ingredient spinosad are readily available at local plant stores. Some formulations of spinosad are approved for organic gardening. The preharvest interval (PHI) for spinosad is 1 day on brassica crops, but always double check labels for rate, PHI, and other critical information before spraying.
Bt products (Bacillus thuringiensis), such as Thuricide, Dipel, and the Monterey and Bonide Bt products, will also control caterpillars but are somewhat less effective than spinosad and will not control beetles or other non-caterpillar pests.
See Extension Publication 2347, Insect Pests of the Home Vegetable Garden for more information.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
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