By Tracy Turner, Ohio State CFAES Technical Writer

Now is the time to scout for black cutworm in Ohio, thanks to the migratory pests that moved into the state from the South in April and are now starting to cause damage to some corn crops in the region.

Kelly Tilmon, an Ohio State University Extension field crop entomologist, says they’ve seen some fields with cutting damage, but at this point the damage doesn’t indicate that the pests have risen to a level to cause a crisis situation.

Already there have been reports of high numbers of black cutworm in traps across the Midwest set up by entomologists to determine the number of moths migrating up from the South, which suggests that the pests may be in some fields, she says.

However, that doesn’t always mean that they will be out in fields in higher numbers.

“Adult black cutworm moths lay eggs that hatch into the cutworm caterpillars,” she says. “Developing larvae feed on emerging corn, meaning growers need to look out for corn with leaf feeding or stem cutting as the crop emerges.

“Although there are some hotspots for egg laying, these predictions are far from exact. Whether or not growers find black cutworms in their fields really depends on the location and conditions of their fields.”

Because the pest can cause stand loss in corn, Tilmon says, “This is a reminder that growers need to be on the lookout.”

Female black cutworm moths tend to lay eggs in fields with heavy weed cover, and as the weeds are killed by herbicide or tillage, the larvae move on to feed on emerging corn, she explains.

Black cutworms can cause severe cutting of the plant, with the resulting stand loss in corn generally associated with below- or at-ground-level feeding injury, which occurs below the growing point.

Another concern for crop damage is the fact that much of the corn in the region is being planted relatively late this spring, as cooler, wetter weather conditions have delayed many growers from getting out into their field.

“So corn will be rather small when the larvae of these pests begin their heavier feeding,” Tilmon says. “Thus the potential for plant injury and subsequent economic losses will be much higher than normal because of the size of the corn.”

Across Ohio, as of the week ended May 22, only 51% of corn was planted, according to the USDA’s National Agricultural Statistics Service. That compares to 84% that had been planted by the same time last year and 66% that had been planted on average during the same time period over the past 5 years.

The agency reported that 28% of corn has emerged as of the week ended May 22, compared to 62% emerged by the same time period last year and 41% emerged on average during the same time period over the past 5 years.

Tilmon recommends growers start scouting for black cutworm as soon as the corn begins to emerge.

“Cutting damage is pretty obvious to see,” she says. “It looks like the plants have been clipped off if the feeding of the plants happens aboveground.

“Underground feeding results in the plants having more of a wilted appearance. So growers should be on the lookout for more than one type of damage.”

Rescue treatments can be applied if necessary, she adds, noting that if the cutting damage is aboveground, cut plants will likely recover if a timely rescue treatment is applied.