Cutworms are the larvae of night-flying moths. In autumn and early spring, the moths lay their eggs near the base of grasses and weeds. As soon as the soil warms in spring, the eggs hatch and the larvae begin feeding. Most cutworms are brown or grayish caterpillars and are difficult to see because they hide in soil during the day. Cutworm feeding often goes unnoticed in lawns, but it's hard to miss in a garden. Seedlings damaged by cutworms are felled like little trees. When you find the tops of young plants lying next to the stubs, cutworms are the most likely cause. You might think that cultivating the soil well before planting vegetables would kill the eggs and larvae, but cutworm eggs survive being tossed about by spades and tillers. To prevent cutworms, keep the area free of weeds in autumn and winter. Winter weeds such as chickweed and annual bluegrass often serve as egg-laying sites for the moths.
Cutworms often appear in the same sites year after year. New beds created in areas that were previously planted with grass tend to have numerous cutworms. Try these tips for additional hints to control cutworms. In fall, closely mow lawn areas near your garden to eliminate egg-laying sites. In late winter, pull up cool-season weeds that establish themselves in beds or rows. Cultivate the soil before directly seeding vegetables. After planting seeds, dust the soil's surface with diatomaceous earth. You'll need to reapply it after heavy rains. Protect transplants from cutworms with collars made from paper towel rolls or milk cartons but into 3-inch-long pieces, or wrap the base of each seedling with aluminum foil. The collars need to extend ? inch below the soil surface. Make a sticky trap from double-sided masking tape pinned to the soil on both sides of a seeded furrow. If needed, renew the stickiness of the tape by painting it with sticky molasses. As soon as seedlings emerge, slip a toothpick or slender wood skewer into the soil alongside each stem. When cutworms try to girdle a stem, the wood will stop them. Purchase beneficial nematodes, sold as Grub-Away, which kills cutworms within a few days.