WEST LAFAYETTE, Ind. — Black cutworm moths are reportedly being captured in pheromone traps throughout the Midwest, according to university entomologists. Iowa, Minnesota, Illinois, Indiana, Missouri and Kentucky all have seen moths, with Indiana reporting peak flights.

Just one state has reported a peak flight, while several traps are reporting low numbers, according to Iowa State University entomologists. Of the 101 traps placed across Iowa, 46 had not caught a single moth as of April 23.

In Illinois, captures have been reported in Champaign, Fayette, Logan, Lee, Mason, Macoupin and Madison counties, according to University of Illinois entomologist Michael Gray.

Purdue University entomologist Christian Krupke said Ohio, Pennsylvania and Tennessee could be affected, as well. He said moth catches in Indiana have varied over the past couple of weeks, but significant egg-laying has occurred.

“Arriving moths are looking for egg-laying sites, for example weedy fields, fields with extensive ground cover, and there are many to choose from,” Krupke said. “Light frosts have little effect on eggs.”

He said moth arrival, along with the use of heat units to predict the beginning of larval activity, gives an indication of the potential severity of the problem and locations of concern. He said he and his colleague, John Obermeyer, will be able to predict with some degree of accuracy when and where crop damage is most likely to occur based on that information.

About 300 heat units (base 50 degrees Fahrenheit) are needed after egg hatch before crop damage will be noted, since larvae need to grow up before they can damage corn. Krupke said it’s too early to scout for black cutworm for two reasons.

First, little corn has been planted, and second, the eggs have not hatched because of cool temperatures. As with most insects, egg hatch is temperature-driven. Hatched larvae grow and feed anytime the temperature is above 50 degrees, mostly on the plant where they were laid.

Black cutworms feed on a variety of hosts, Krupke said. Corn is not a preferred food, but larvae will feed on corn as weeds are killed by herbicides, leaving corn as their only food source. Based on the growth development model of about 300 heat units from egg hatch to early 4th instar, when larvae begin to feed cut plants, he said the southern counties in Indiana are about a third of the way there.

Even with all this information, Krupke cautions that flights don’t reliably equate with damage, partly because only the males are caught in the pheromone traps. All experts recommend scouting fields as plants emerge, and throughout the growing season.

Gray said a single cutworm can cut an average of 3-4 plants during its development. Cutting tends to occur most often at night or on dark, overcast days.

Fields are at greatest risk in the 1-4 leaf stage. An early warning sign of potential economic damage includes pinhole feeding injury to leaves caused by the first 3 instars. A nominal threshold of 3 percent cutting of plants traditionally has been used as a point where growers should consider rescue treatment.

Gray said many Bt hybrids offer some protection, but not all offer adequate protection. He recommended the Handy Bt trait table prepared by Chris DiFonzo at Michigan State University and online at http://msuent.com/ assets/pdf/28BtTraitTable2015.pdf to determine the level of protection provided by a producer’s chosen hybrid.

As for rescue treatment, Krupke said foliar applications of pesticides are the best approach, but it must be done while the larvae are small, for best efficacy.

“When cutting starts, it is too late to get good control and they become difficult to kill,” Krupke said.