Cutworms: Identifying and Getting Rid of Cutworms

Brown caterpillar cutworm on a stem - stock photo

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In This Article

Cutworms are the larvae in caterpillar form of nocturnal moths. Even though these adult moths do not damage crops, the larvae often destroy young plants by eating the stems at or near the soil line. Because they can cut down young plants (especially seedlings) so quickly by moving up the plants and biting the buds, shoots, and foliage, they are called "cutworms."

Keep an eye out for cutworms on young tomato plants, asparagus, beans, cabbage, carrots, celery, corn, lettuce, peas, peppers, and potatoes. A few species do feed on turfgrass. Cutworms can damage lawns, as their feeding creates small spots in the turf that are more noticeable in manicured golf greens rather than in home lawns.

Are Cutworms Harmful to Gardens?

Black, bronzed, and army cutworms feed at night and hide in plant debris during the day. They can cause severe injuries to the vegetable plants mentioned above and to well-cared-for lawns. Meanwhile, the variegated cutworm climbs the stems of trees, shrubs, and vines, eating leaves, buds, and fruit. Glassy cutworms are one of several species that can stay in the soil and feed on the roots of new transplants and young plants, which they are fond of because the stems of these plants are more tender. Therefore, the damage is usually most serious in the early season, cutworms being most active in spring though still active in summer. The number of cutworms varies year by year, and when their numbers are high, they can be disastrous to the garden.

Identification

Cutworms of all species look quite similar. All are smooth and have very few hairs. About two inches when mature, they curl into a "C" shape every time they are disturbed. Species range from brown to tan to pink, green, gray, and black. Some are one color; others are spotted or striped. Some appear dull; others look rather shiny.

How to Get Rid of Cutworms

Remove larvae by hand and then crush them or drop them into soapy water. Create a three to four foot buffer of dry soil on the edge of a susceptible or damaged garden bed, which will deter any other cutworms nearby. Take away any plant residue and weeds, both of which are attractive environments for young cutworm larvae to hide in during the day (some can survive in weeds through the winter). Use compost, not manure, because egg-laying tends to occur in green manure.

To continue to keep cutworms out, use a barrier. Surround transplants with protective collars made of cardboard, tin cans, aluminum foil, or toilet paper. Insert them halfway into the soil, around each plant so that one end is pushed a few inches in the soil and the other is a few inches about the ground. Bacillus thuringiensis mixed with molasses and grain can also be used as bait. The best contact insecticides for tomatoes contain cyhalothrin, esfenvalerate, and cypermethrin.

Warning

If you want to grow an organic garden, avoid using pesticides. Only apply a pesticide with carbaryl, cyfluthrin, and/or permethrin for climbing cutworms if there is a big infestation, and apply it in the evening before cutworms emerge. Be mindful of the type of pesticide and read the label. To avoid consuming any of the residual pesticide applied to the damaged plants, be sure to count the number of days between when the pesticide has been used and when the crop is harvested.

Prevention

Till your garden in autumn to kill any larvae or pupae in the soil. In the mornings, check plants while the damage would be fresh. Keep an eye out for wilting plants and plants that are cut off near the ground. Droppings on the ground could also be a sign of cutworm feeding. Another way to confirm the presence of cutworms is to run your hand over the soil, over soil clumps and other places where they could be hiding, within about 12 inches of the damage. If there are cutworms, they will curl up into a "C" shape. Control and prevention are necessary for some crops from seedling to harvest like tomatoes, peppers, and celery. Beneficial nematodes feed on cutworms as well as squash vine borers, pillbugs, grubs, fungus gnats, root weevils, and armyworms. Finding ways to welcome these nematodes to the garden could prevent the presence of cutworms too.

Article Sources
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  1. Cutworms in Home Gardens.” UMN Extension, 2019.

  2. Layton, PhD, Blake. “Control of Insect Pests In and Around the Home Lawn.” Mississippi State University Extension Service, 2021.

  3. Griffin, Randall, et al. “Tomato Insect Pests | Home & Garden Information Center.” Home & Garden Information Center | Clemson University, South Carolina, 8 July 2021, hgic.clemson.edu/factsheet/tomato-insect-pests.