Cabbage Loopers

This article was originally published on June 18, 2012 and expired on June 25, 2012. It is provided here for archival purposes and may contain dated information.

Cabbage, lettuce, and turnips currently are hosting infestations of pale green worms. Individual larva has a white stripe on either side of the body. The larvae, which crawl along raising their mid-sections, are commonly referred to as inch worms. They are about an inch long, but the name accepted in university circles is the cabbage looper.

Cabbage loopers are the larvae of a brown moth that lays its eggs under the cover of night. The eggs are pale green and are usually laid on the upper surface of the leaf. A similar pest of cabbage, the imported cabbage worm, differs from the looper. The adult moth is white instead of brown, sets its eggs during the day instead of the night, lays yellow eggs instead of pale green eggs, and deposits those eggs on the underside of the leaf instead of the upper surface. Both can seriously damage cabbage and some other vegetables by chewing large odd-shaped holes in the leaves. They also contaminate leaf material with small green or brown fecal pellets. Multiple generations occur each season making the looper and its comrade a full season insect pest. Loopers do not overwinter in the state.

Loopers are often naturally controlled by various parasite predators. The homeowner should, therefore, use a pesticide that eliminates only the looper and not beneficial organisms. The perfect tool for this pest is the biological pesticide Bt kurstaki. Bt kurstaki, Bacillus thuringiensis kurstaki, is a bacteria that infects only moth larvae and causes the moth larvae's stomach to basically hemorrhage or ulcer the pest to death. Since this version of Bt is specific to moth larvae and not to other types of insects, such as beetles, wasps, etc., it can be used without having an effect upon the moth's natural predators. Additionally, the bacteria only affect moth larvae and not humans, so its use in the garden is very safe. Gardeners should time applications at one to two week intervals and should begin either when the larvae are very small or when the white, imported cabbage worm moths are observed clustering on vegetables in the garden. As with any pesticide, even this relatively safe one, the gardener should always read and follow label directions before buying, mixing, using, storing, or disposing of a pesticide or pesticide container.

Pull date: June 25, 2012