Cutworms are the caterpillars (larvae) of night flying moths. Cutworms are generally a problem during May and June. Surface cutworms such as the black cutworm clip off transplants at or just below the soil level and are active at night. Look for cut off seedlings and dig around the base of the plant to expose the caterpillars. The caterpillar is gray to black, with a lighter stripe down the middle of its back. Other species are a dull brownish color. Mature caterpillars can reach 1 inch in length and curl up into a C-shape when disturbed. Climbing cutworms look like surface cutworms, but climb up the stems of plants and feed on stems, leaves, buds, and flowers.
To prevent damage from surface cutworms, wrap seedlings and transplants with cardboard collars to protect them from cutworm damage. A simple collar can be made from a paper cup with the bottom removed. Push the cup into the soil to hold it in place. Cardboard tubes from paper towels or toilet tissue can be cut to size for collars. For climbing cutworms, inspect plants at night with a flashlight and pick off and destroy any cutworms.
Black cutworm larvae curl into a tight "C" shape when disturbed. Photo: Roger Schmidt, University of Wisconsin-Madison, Bugwood.org
Cutworms on a leaf. Photo: Maryland Department of Agriculture