Warmer weather and newly emerging corn coupled with reports of large populations of black cutworms and armyworms reported last month in Indiana and Kentucky means Ohio growers could start to find larvae from these pests in their fields over the next few weeks.

Now that the region is experiencing more suitable planting days, growers could see some fields with heavy feeding by these pests as soon as the second or third week of May, an entomologist with the College of Food, Agricultural, and Environmental Sciences at The Ohio State University said.

Black cutworms, which are migratory pests, have been reported in the neighboring states of Indiana and Kentucky in significant numbers in traps set up by entomologists to determine the number of moths migrating up from the South, said Andy Michel, an Ohio State University Extension pest expert. Large numbers of armyworms have also been caught in the Kentucky traps, Michel said.

Both insects can cause significant stand loss in corn, while armyworms can also be a significant pest of wheat, said Michel, who also has an appointment with the Ohio Agricultural Research and Development Center. Black cutworms are especially attracted to chickweed and other broadleaf weeds, he said.

OSU Extension and OARDC are the statewide outreach and research arms, respectively, of the college.

“Although black cutworms aren’t a widespread problem throughout Ohio, growers whose fields were covered in weeds last week are the ones who should start scouting now soon after corn emergence,” Michel said. “Black cutworms tend to infest fields with significant ground cover and weed presence.

“Growers who have fields with a history of black cutworms are more likely to have cutworms in their fields this year.”

Corn from the V2 to the V6 stage is vulnerable to damage and cutting by armyworms and black cutworms, he said.

Females tend to lay eggs in fields with heavy weed cover, and as these weeds are killed by tillage or herbicide, the larvae move on to feed on emerging corn, Michel said. Black cutworms can cause severe cutting of the plant. The resulting stand loss in corn is generally associated with below- or at-ground-level feeding injury, which occurs below the growing point, he said.

“Recently emerged corn could start exhibiting pinhole-sized feeding very soon,” Michel said. “With the warm weather we’ve had, and if there is enough extra material such as weeds on the field, we can expect to see armyworm and cutworm eggs hatching with some development in the larvae, leaving it easier for growers to scout.

“Usually when corn is in the V2 stage, it is really vulnerable to cutworms, and the larvae could be large enough to see.”

Growers should scout their corn crops until the plants reach the V6 growth stage, Michel said. To scout, growers should check 20 plants in five locations throughout the field for larvae or signs of injury to the plants. Signs of injury include cutting of the leaves or cutting of the plant and pinhole damage to the plant.

“If you do have an infestation, you could have some significant stand loss, with areas that may need replanting or rescue treatments,” Michel said. “Growers who find more than 3 percent of plants damaged in their fields that are in growth stages V2 to V6 with larvae that are less than 1 inch in length can consider spray applications.

“Growers who find black cutworm infestations may find that rescue treatments are more effective than preventive treatment, including insecticidal seed treatment. However, certain varieties of Bt corn (those with Cry1F or Viptera) will offer control of black cutworm.”