Cutworms are larvae of various species of moths that fly at night belonging to the family Noctuidae. The larvae are called cutworms because they cut down young plants when feeding on their stems at soil surface levels or below the soil surface. The adults do not cause damage and fly at night only. Common plants attached by cutworms include beans, cabbage, asparagus, carrot, celery, peas, potato, and tomato.
Description of Cutworms
Cutworms range in color from brown or even tan to green, gray or black. While some cutworms are spotted or striped, others can have a uniform coloration throughout. Similarly, the larvae can look shiny or dull. When they are disturbed they curl up and form a tight “C.” Adult moths are of moderate size and range in colors and shades mostly ranging from gray, brown or black with various spots. They typically measure about an inch in length and their wingspan measures 1-1/2 inches.
Life cycle of the Cutworm
Cutworms remain dormant as eggs or larvae during winter. Female moths lay hundreds of eggs, sometimes in clusters, on plant residue and low-growing plants. Young larvae grow by feeding on plant foliage or small roots or weeds until they reach about ½ inch in length. Small larvae are attracted to newly emerged weeds and feed on stems by cutting or burrowing into them. Cruciferous plants are commonly attacked by cutworms. Larvae grow up to 2 inches in length and can go through 3 generations per year.
Checking the garden regularly for cutworms can identify their presence and treatment can begin early. In the mornings it is easier to see the damage to plants especially near the surface level. For some plants like peppers, celery, and tomatoes, control and monitoring may be regularly required until the harvest is complete.
Use compost instead of green manure which will discourage the eggs being laid in the manure. Tilling the garden before planting is helpful in exposing and killing overwintering larvae. If you till the garden in the fall it is beneficial because it helps to destroy or expose the overwintering larvae or pupae. Placing aluminum foil or cardboard collars around plants helps controlling cutworms by creating a barrier that physically prevents the larvae from feeding and destroying the plants.
Use of insecticides is generally not necessary unless there is a severe problem. Common insecticides are carbaryl, cyfluthrin, and permethrin.