Scout Cornfields for Black Cutworms

With temperatures warming and corn emerging in some parts of the state, Indiana farmers should start scouting for signs of black cutworm, saysJohn Obermeyer, integrated pest management specialist at Purdue University.

Black cutworms are migratory pests that can cause significant damage to young corn crops. Newly hatched larvae feed on weeds and the leaves of small corn plants while larger larvae can notch, or cut, the stems of seedlings immediately below the soil surface.

“Scouting the field is the only way to know if problems exist, especially catching the damage early before plants are killed or damaged such that they are delayed in growth,” Obermeyer writes in the latest issue of Purdue’s Pest and Crop newsletter.

Black cutworm larvae range in size from one-eighth of an inch when newly hatched to 2 inches fully grown. Larvae are light gray to nearly black and have a coarse texture.

Adult black cutworm moths are brown with a distinctive “dagger-shaped” marking on the edge of their wings, Obermeyer said.

Moths arrive from the Southwest on storm fronts and typically start appearing in Indiana in early April. Females are most active at night and prefer to deposit their eggs in low-growing, dense vegetation.

Weedy fields, especially those with chickweed, are especially vulnerable to a black cutworm infestation, Obermeyer said. “Timing of winter-annual weed control is important concerning black cutworm egg-laying and larval development,” he said.

If left unchecked, a single black cutworm larvae can cut four corn plants in its lifetime. “Foliar insecticides, if applied in a timely manner, are very effective in controlling black cutworm,” Obermeyer said.

To read Obermeyer’s full article, “Black Cutworm: Now is the Time to Scout,” go to

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