What's Bugging You? Cutworms


COMMON NAME: Cutworm, Miller's Moth

DESCRIPTION: ADULTS - Mottled grayish or brownish moths with a 1 - 1 1/2 inch wingspan. The hind wings are paler in color. Nocturnal in nature, they are attracted to street and porch lights. EGGS - The eggs are laid in the soil near food plants. LARVAE - The larve are grayish or brown, often with stripes or spots (I have observed ones with triangle-shapes on the sides). They can grow to 1 1/2 - 2 inches in length. If disturbed, they will curl up. Cutworms are seldom seen in the light of day. PUPAE - The larvae pupate in the soil, sometimes making a sort of earth "shell' around them.

LIFE CYCLE: There may be up to five generations per year, especially in warmer climates such as ours. The eggs in the soil hatch and the larvae feed on the available plants until they have fully matured. They then burrow into the soil and pupate. If early enough in the year, they will emerge as a new generation of adults, seek a mate, and lay more eggs to repeat the cycle. Cutworms overwinter in the soil as larvae or pupae.

HOST PLANTS: All garden vegetables, especially vulnerable are newly sprouted or transplanted seedlings.

TIME OF YEAR: Early spring (approx.. march in Sierra Vista) to frost in early winter.

WHAT TO LOOK FOR: If you walk to your garden and see your new seedlings toppled like a clearcut forest, then you can be fairly assured that the cutworm is the culprit. They cut the stems clear through just above or below the soil line.

PROBLEMS AND DAMAGE: As might be expected, severe problems arise if all your seedlings are cut down. If they don't happen to get the main stem the first night, you can be sure they will be back for another meal the next.

CULTURAL CONTROLS: Deep plowing, tiling, or digging in the late fall and again in the early spring will expose eggs and overwintering larvae to the elements and predators. Handpick larvae at night using a flashlight. Remove winter mulch in the early spring to get rid of any pests before they come out of hiding. Some folks say that if you place a toothpick, nail, etc. upright next to the seedling, the cutworm will not be able to fell the plant. You may also try digging in the soil around a felled plant to expose the pest as it often settles down to sleep right next to its latest victim.

COMPANION PLANTING AND REPELLENTS: Extract of pineapple weed or sagebrush is supposedly an effective repellent.

TRAP PLANTS OR BAITS: Cutworms love cornmeal, but cannot digest it. Encircle your plants with this material and they may get a fatal stomachache. Another bait is a sticky combination of molasses, water, and bran that can be set out on the ground and the critters will become hopelessly entangled as they feed.

MECHANICAL CONTROLS: The tried and true method of exlusion is to encircle the seedling with a "collar" approximately 2-3 inches in height. Bury the collar half under the soil line and leave the rest above ground. The collars can be made of just about anything: bathroom tissue rolls cut in half work perfectly, as do rings cut out of plastic bottles, cans, PVC, paper cups, etc. Mulch around plants with oak leaves, straw, crushed egg shells, wood ashes, or anything else that will irritate their soft bodies as they try to crawl across it. A circle of diatomaceous earth will cut them up and eliminate the problem.

NATURAL CONTROLS: If they can find them, birds, toads, lizards, moles, firefly larvae, soldier and ground beetles all love to eat cutworms. These pests are also parasitized by Braconid and Trichogamma wasps, Tachinid flies and parasitic nematodes. Bats and swallows make short work of the adults.

BIOLOGICAL INSECTICIDES: Bacillus thuringiensis (BT) Dipel, Thuricide, etc.) is effective as reportedly is Bacillus popilliae (milky spore).

CHEMICAL CONTROLS: Please consult the Agricultural Extension Agent or a Master Gardener Volunteer for current recommendations. Phone 520-458-8278 ext 2141 in Sierra Vista, or 520-384-3594 in Willcox. Whatever you use, FOLLOW LABEL DIRECTIONS EXACTLY, and take the necessary precautions to protect yourself, other humans, non-target animals, and the environment.

T.J. Martin
April, 1992