Cutworms

Cutworms

By Kimberly Stoner
Department of Entomology
Connecticut Agricultural Experiment Station
123 Huntington Street
P.O. Box 1106
New Haven, CT 06504-1106

Telephone: (203) 974-8480 Fax: (203) 974-8502
E-mail: Kimberly.Stoner@ct.gov

Where and When to Look

Cutworms typically do most of their damage just after plants germinate or are set out in the field. There are many different species with different habits. Some species chew the plant stem at the soil surface, not eating the whole plant, but making the plant fall over. Other species climb the plant stem and feed on leaves and buds, and a few species live in the soil and feed on roots and underground stems. Nearly all garden plants are attacked. Most cutworms pass the winter in the caterpillar stage, so they are already quite large (up to 2 inches) when you set out your plants in the spring. Typically, cutworms continue feeding through the spring, then change into hard, dark brown pupae, and then into moths during the summer. The adult moths lay eggs in the fall that hatch and feed on grasses or weeds until winter. There are some species, however, such as the black cutworm, that overwinter in the south, then fly up north and lay their eggs in the spring.

Most of the time, the caterpillars feed at night, but can be found during the day curled up in the soil near the damaged plants or hiding under debris.

Description

Larvae: Most cutworm larvae (caterpillars) are dark brown, gray, or black, and their skin may be covered with smooth black granules. They have hard heads and soft bodies between 1 and 2 inches in length when fully grown.
Pupae: The pupae are hard, dark brown cases about 1 inch in length.
Adults: The adults are moths, typically 1 1/2 to 2 inches in wingspan, with various patterns on the wings. They fly at night.

Control Methods

Natural: Beneficial nematodes that attack cutworms may be effective, particularly when the soil and weather are damp. Survival may be improved by applying the nematodes at sunset, so they can have an opportunity to seek their hosts under cool, dark conditions when the caterpillars are active. Follow instructions for application carefully.

A stiff collar, at least three inches high and buried one inch deep around the stem of each plant, is an effective barrier. Collars can be made of cardboard, like paper cups or milk cartons, or of plastic or metal.

If tall grass and weeds are eliminated at the end of the season in the fall, many cutworm populations will be greatly reduced the following spring. Thorough cultivation in fall and again before planting in spring can expose larvae in the soil.

Abrasive or irritating materials such as diatomaceous earth or crushed eggshells around the base of plants will kill or deter cutworms crawling on the soil surface.

You may be able to hand-pick cutworms by digging shallowly around the base of cut-off plants, and by checking your plants at night.

Chemical: Carbaryl is available in formulations labeled for control of cutworms. Either a bait treated with carbaryl or a foliar application to the plant may be effective on cutworms feeding above the ground. Baits should be spread in late afternoon so they will be fresh when the cutworms feed at night. Use rubber gloves and apply the bait only to the soil. Follow the cautions and instructions on the label.

Summary

Cutworms are a diverse group of caterpillars that vary in feeding behavior and life history. They typically feed at night, and do most of their damage early in the season on young plants. Plants can be protected with collars, or cutworms can be controlled with beneficial nematodes, barriers of abrasive materials, or with insecticidal baits or sprays.