Corn seedlings may be vulnerable to cutworm damage in southeastern South Dakota counties and corn growers are encouraged to inspect their fields as soon as possible.

That’s a recommendation from Mike Catangui, extension entomologist at South Dakota State University, after receiving several reports from the affected areas.

Significant cutworm activity was reported in about 400 acres of corn in Minnehaha and Lincoln counties on May 30, with most of the damage caused by black cutworms.

Approximately 900 acres of corn seedlings have already been sprayed for cutworms in Union County as of June 1. Most of the affected areas there are close to the Iowa border.

Catangui says there have also been reports from Yankton and Clay counties.

Cutworms are active at night and hide under loose soil during the day. Scouting during the day involves scratching the soil surface to expose hidden larvae.

Insecticide treatment may be considered if 5% (1 in 20 seedlings) of the seedlings show signs of cutting or leaf feeding, and the larvae is still less than an inch long.

Insecticides labeled for use on corn to control cutworms include Ambush 2E, Asana XL, Lorsban 4E, Pounce 3.2EC, and Warrior. Catangui reminds producers to read and follow all directions on the label.

"Two species of cutworms commonly infest corn seedlings in South Dakota," says Catangui. "Dingy cutworms overwinter as partially grown larvae in the soil then resume feeding in the spring."

Catangui claims black cutworms arrive in the field as moths and then lay eggs on weedy, wet fields in spring. "Larvae of black cutworms are more damaging because they cut the corn growing points from under the soil. In general, cutworm infestations are more common in fields with more plant residues, weeds and moisture," says Catangui.

Source: Mike Catangui, 605-688-4603.