Cabbage loopers are 1½ inches long caterpillars with two pale white stripes down the back, one on each side. Loopers have legs at the front and back and several more in the middle and so they move with a peculiar humpback or looping crawl.
Loopers are the offspring of gray night-flying moths with 1½ to 2 inch wingspans; each forewing is marked with a silver spot in the middle. Moths lay greenish white, dome-shaped eggs singly on leaves. From these eggs, the larvae loopers emerge.
The larvae caterpillars feed voraciously for two to four weeks reducing leaves to nothing more than midribs. Then the loopers spin a cocoon, attach it to a leaf, and rest for one to two weeks before emerging as moths and starting the cycle again. There are two to seven generations a year.
Cabbage loopers are common through most of the United States and southern Canada.
Target Plants: Loopers chew large holes in leaves of broccoli, Brussels sprouts, cabbage, Chinese cabbage, cauliflower,collards, kale, kohlrabi, lettuce, beans, celery, parsley, peas, potatoes, radish, spinach, tomatoes, rutabagas, and turnips. Loopers can destroy whole plants.
Feeding Habits and Damage: Loopers chew large irregular holes in leaves and bore holes into heads of cabbage and lettuce. They also chew into tomatoes. Seedlings attacked by loopers are usually destroyed.
Organic Controls: Use Bacillus thuringiensis var. kurstaki (Bt) or spinosad for serious infestations. Apply neem to large infestations. (Don’t spray when heads form on cabbage, collards, and lettuce.)
Organic Control Calendar: Here is what you can do seasonally to control cabbage loopers:
- Before planting: Attract parasitic wasps by planting pollen and nectar plants around the garden. Till in cabbage family crop residues before adults emerge in spring. Turn or till the soil to destroy pupae.
- At planting time: Cover plants with row covers. Spray garlic or hot pepper sprays at the edge of planting beds to repel moths and loopers. Set up commercial insect traps with floral lures to attract moths; this can reduce the number of eggs laid in the garden.
- While crops develop: Handpick several times a week. Wasps parasitize cabbage loopers; if you see eggs on caterpillars leave them to their fate. Also leave chalky white loopers alone; they are infected with a virus. Apply hot pepper spray to plants weekly through the season to repel moths and loopers. Spray larvae with Bt. For severe infestations, spray loopers with garlic oil or pyrethrin.
- At harvest and after harvest: Harvest crops when still young to minimize damage to maturing plants. Since cabbage loopers feed on outer leaves, you can often just pull the marred leaves from the heads of cabbage or lettuce and still get a good harvest. Clean the garden of all plant debris to prevent over-wintering in debris. Put all wrapper leaves at the center of compost pile. Turn or till the soil to destroy pupae.
Natural Predators: Trichogramma wasps, lacewings, lady bugs. Animal predators include Baltimore orioles, bluebirds, chickadees, cowbirds, flickers, redwing blackbirds, robins, sparrows, and starlings, also skunks and toads.
Scientific Name: Trichoplusia ni