Cutworm Damage to Seedling Corn

There are multiple species of cutworm capable of damaging seedling stage corn, with the Black cutworm and Dingy cutworm being the most common. Cutworms typically damage corn from emergence through about the V5 to V6 growth stage, when the crop will be approximately 15 to 18 inches tall. Management of cutworm can be based either on prevention, or on a curative strategy.

Dingy and Black cutworm are the larval stages of Lepidoptera moths, and the adult moth of both species prefers to lay eggs in areas covered by dense vegetation. Dingy cutworms hatch from eggs laid in the fall, and are most frequently observed where this type of vegetation cover was present during the late summer and early fall of the previous growing season. Ideal sites for Dingy cutworm include fields where corn follows sod, alfalfa, small grains that were allowed to volunteer back after harvest, full season soybeans, or a very weedy previous crop of corn. Black cutworm, on the other hand, hatch from eggs laid in the same spring in which the cutworm larvae feed. Ideal sites for Black cutworm include corn planted into a growing cover crop and/or fields where weeds were allowed to grow prior to planting. While a few Black cutworm pupae may overwinter as far north as Kansas and portions of Nebraska, the primary source of Black cutworm is moths brought north on wind currents from areas farther south.

Cutworm usually feed initially on leaf tissue. Damage appears as either a row of small, circular holes across the leaf blade, or as missing segments of leaf that are irregularly shaped, or both. Damage from leaf feeding is of very minor importance and rarely impacts yield. As the cutworm larvae grow, they will begin to cut plants at or below the soil surface. Plants cut at the soil surface often survive, but will be at a competitive disadvantage to surrounding plants. The dryer and warmer the soil surface, the deeper the cutworm will feed, and the plant will die if the growing point is damaged during this “cutting” process. As both the corn and the larvae grow, cutworm will start to burrow into the stalk. They enter just below the soil surface and feed upward inside the stalk, killing the plant.

Preventative tools for control of cutworm include insect control traits, seed treatments containing a neonicotinoid insecticide, and insecticides applied during planting or prior to emergence. Agrisure Viptera is the only insect control trait with activity on Dingy cutworm, and is also by far the most efficacious of the traits with activity on Black cutworm. Seed treatments containing a neonicotinoid insecticide (i.e. CruiserMaxx Corn and AvictaComplete Corn) provide some activity on cutworm, and will be most efficacious when cutworm hatch coincides closely with crop emergence and cutworm pressure is light to moderate. Many insecticides are labeled for control of cutworm, including both granular and liquid insecticides that can be applied during or immediately following planting.

A curative approach to cutworm management must include regular scouting for cutworm damage. Implement control in fields where leaf feeding and/or cut plants exceeds 5% and cutworm are still present. Cutworm hide beneath the soil surface during the day and can be very difficult to find. When looking for cutworm larvae, carefully dig in the soil around recently cut plants; use a pocket knife or similar tool to carefully move clods and/or remove soil in layers of a ¼ inch or less at one time.