Cut Cutworm Losses

By Ric Bessin, Extension Entomologist

Cutworms are cool-weather, early-season pests of many cultivated plants. Cool conditions and excessive moisture has delayed planting and slowed growth of some crops this year, extending the period of vulnerability to cutworms.   Cutworms will attack plants from the seedling stage until they are about 6 to 12 inches or so in height, depending on the crop; however, plants that are up to about 4 inches in height are most vulnerable.

Figure 1. Black cutworm at base of corn seedling (Photo: Ric Bessin).

There are several species of cutworms that can be serious pests, including black cutworm, bronze cutworm, and dingy cutworm. Cutworms are often active and feeding on winter annual weeds before a crop is even planted. When crops emerge, cutworms have reached a size in which they are able to cause damage.

Generally, cutworms hide beneath residue or in the soil on clear sunny days.  Their burrows are often within 6 inches of the plant on which they are feeding. At night or on overcast days, cutworms leave their burrows to feed on various plants. To sample for cutworm, dig about 2 to 3 inches deep in a 6-inch radius around cut plants.

Management

There are several insecticides that provide excellent cutworm control, but the challenge is knowing when to use them. I recommend scouting fields for cutworms twice a week until plants reach 6 inches in height, then weekly thereafter.  Some of the traited field corn hybrids provide cutworm control.