Cutworms are seedling destroyers that attack in the night. One moment your seedlings are growing strong and vigorous, the next, it looks like someone came in with a pair of scissors and snipped each seedling in half.
Cutworm caterpillars are the larvae of a number of species of moths in the family Noctuidae. The moths themselves are night flyers and do not damage plants. Females lay hundreds of eggs; some species in the spring, others in late summer and early fall. Eggs overwinter on plants and plant debris, and larvae in the soil. A wet spring means more cutworms.
Clemson University – USDA Cooperative Extension Slide Series, bugwood.org
Once hatched, the larvae first feed on plant roots until they reach about 1/2" in length, then move onto plants, curling themselves around stems to chow down. They grow to about two inches in length. Since they eat after dark, a seedling can be fine at sunset and topless at sunrise. There can be as many as three generations per year.
Cutworm caterpillars will eat the seedlings of just about anything, including corn, potatoes, peppers, tomatoes, kale, broccoli, cauliflower, and beets. Sunflowers are a favorite. Some species climb trees, shrubs, and vines and eat the buds, fruits, and leaves. Others spend their lives underground eating roots. Some prefer turf grass.
Not all cutworms look alike. They can be black or gray, white or tan, pink or green. They can be dull or glossy, or have stripes. Since they are often the same color as the soil, cutworms can be hard to see. If you run your hand lightly over the ground and disturb one, it will curl up in a tight "C" shape. Droppings around the plants are another clue that cutworms are present.
Eddie McGriff, University of Georgia, Bugwood.org
How to prevent and control cutworms:
Practice good garden hygiene. Clear out the remnants of spent crops and weeds from your vegetable garden at the end of the growing season. The moths lay eggs on weeds and detritus. The eggs then overwinter and hatch when it warms up. Till or rake the soil in fall and before planting in spring; this kills any overwintering larvae. Keep the plot weed-free.
Use cutworm collars. Cutworm collars are a physical barrier placed around a transplant or newly emerged seedling, which prevents the cutworm from reaching the plant. Collars can be made from toilet paper or paper towel rolls, aluminum foil, cardboard or any sturdy material that can be formed into a circle. Collars should be about four inches long. Push each one halfway into the soil so cutworms can't get under it. Collars can be removed once seedlings' stems toughen up.
Create a buffer. Cutworms don't like dryness. Leave three to four feet of dry, bare soil around the edges of the garden. Cutworms won't cross it. Or sprinkle diatomaceous earth or corn meal containing Monterey Bt over the soil.
Kill the larvae. Handpick the larvae you see: run your hand over the soil and move soil clumps where larvae can hide. While cutworms can be controlled with both organic and synthetic pesticides, the caterpillars favor edible crops. Pesticides on anything you plan to eat should be chosen carefully and used sparingly.
Cutworms can be frustrating, especially if you've gone to the time and effort of starting your own transplants from seed. They are most problematic in early spring, and thankfully are less of a problem as the growing season progresses.
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