Cabbage looper larvae eat large, irregular holes in the outer leaves of cabbage plants, sometimes eating into the heads of cabbages. Heavy infestations often result in skeletonized plants, as all but the leaf veins are usually eaten. Cabbage loopers can be responsible for reduced yields, heads which fail to form, and the contamination of the edible portions of the plants.

Description:

Cabbage looper larvae are light green and 40 mm (1 1/2 inch) long when mature. Older larvae have thin white lines running the length of each side. Loopers get their name from their peculiar walking behavior. They have three pairs of slender legs at the front of their body and three pairs of stout prolegs on the last 1/3 of the abdomen and no appendages in between. They move by gripping with the front legs and dragging the back legs forwards while arching the back. They then grip with the rear prolegs and push forward to straighten the "loop." The cabbage looper moths are nocturnal and are rarely seen during daylight hours. The moths are grayish brown with a wingspan of 40 mm (1 1/2 inch). The front wings are mottled brown with a small silver figure-8-shaped spot near the center, while the second wing pair is uniformly brown.

Life Cycle:

Cabbage loopers overwinter as pupae attached to host plants and other nearby objects. The adults emerge in the spring and lay several hundred eggs singly on the upper surfaces of host plant leaves. Larval development may be completed in two weeks if weather is favorable, and the cabbage looper can have three or more generations per year in the northern United States.

Control:

- Crop remains should be cleaned up immediately after harvest and fields should be plowed under to destroy overwintering pupae.

- Weeds such as wild mustard, peppergrass and shepherd's purse can serve as alternate hosts for cabbage loopers and should not be allowed to grow in or near gardens and fields.

- Early planting may allow harvesting before damage becomes significant.

- Bacillus thuringiensis, a bacterial pathogen of butterfly and moth larvae, can effectively control the cabbage looper when applied weekly as a dust.

- Insecticides are available for use in home gardens which, if used according to label directions, provide effective control. Cabbage loopers display a remarkable talent for avoiding insecticide-treated plant tissue--care must be taken to treat plants thoroughly or the larvae may eat the untreated portions of the plant.

By David Gadoury, David B. Wallace and Richard A. Casagrande. Revised 1999