If you have some time to enter the Lilliputian world of an insect, spend a few moments and gaze with amazement at the strange locomotion of the cabbage looper. Of all the creatures of Creation, this little critter is fun to watch for all ages.
The insect is a Lepidopteran in the Noctuidae family. Adults, commonly known as owlet moths, are nocturnal. The larvae have the common name cabbage looper ( Trichoplusia ni ) from the preferred host plants in the cabbage family and its looping crawling behavior.
The cabbage looper loops as it moves because it lacks legs in the center of its abdomen. Larvae travel by doubling-up while pushing the posterior end of its body toward the anterior, its head.
As you gaze at this critter, count the legs that are found on both ends of the larva. Near its head are three pairs of legs and near the posterior end of its body are three pairs of prolegs, small fleshy stubs found on its bottom surface.
The looper larva is a pale green caterpillar about 1½ inches in length. Pale yellow, skinny stripes extend the entire length of the sides and back of its thin, smooth skin. Tiny trichomes, hairs, protrude from its skin. As larvae mature the skin color darkens.
Adult moths have a 1½ inch wingspan. Forewings are gray-brown with silver-white spots arranged in a V or U-shape; hindwings are lighter brown with darker brown near edges. Moths emerge from cocoons in the spring and mate. Females lay eggs during the night on leaves of the host plant. Members of the Brassicaceae , the cabbage, family are preferred but more than 100 plants can host looper larvae.
Larvae hatch in a few days and commence feeding on the host with their chewing mouthparts. In the early stages, caterpillars feed on the undersides of leaves, resulting in tattered patterns of the thinning leaves. As larvae mature they chew large holes all the way through the leaf.
The looper in the accompanying photo is feeding on a leek blade. Notice the three pairs of legs near the head, three pairs on its posterior, and lack of legs on its abdomen. Chewing mouthparts are visible and the larva has worked its way across the blade. It looks as if a razor blade has precisely shaved a stripe across the blade’s epidermis.
Larvae spin cocoons when about a month old. They pupate and in a few weeks a new generation will have begun. Controlling loopers begins with daily crop monitoring. Treatment depends entirely upon the gardener. Most of us are no longer squeamish about the most effective treatment --- outright squishing of the caterpillars.
An organic control is to treat foliage with Bacillus thuringiensis (Bt), a bacteria sold under the commercial label Dipel. Larvae ingest the Bacillus thuringiensis and die. Bt has the advantage of having a no-wait period to harvest. Always follow directions of any product before use.
Adults are lured to light at night. Night lights are an effective means to capture the moths.
Ellen Peffley taught horticulture at the college level for 28 years, 25 of those at Texas Tech, during which time she developed two onion varieties. She is now the sole proprietor of From the Garden, a market garden farmette. You can email her at gardens@suddenlink.net
This article originally appeared on Lubbock Avalanche-Journal: Gardening for You: Strange locomotion of cabbage loopers
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