Black cutworm moth presence has never been greater in Indiana, says Christian Krupke, Purdue Extension entomologist. Pheromone trap cooperators throughout the state have captured an abnormally large number of the moths over the last few weeks, he says. "The key question is whether or not the egg-laden moths arriving in the state will find fields attractive to lay eggs in.”
While barren fields are not appealing places to lay eggs, the black cutworm has a broad range of hosts, so fields showing green, yellow and purple weeds are still at the highest risk. The moths are particularly attracted to winter annuals, such as chickweed and mustards.
"Remember, corn is one of the black cutworm's least favorite foods," Krupke says. "It just so happens it is the only plant remaining by the time larvae have emerged and weeds have been killed."
Typically, cutworm larvae will starve if weeds are treated with tillage or herbicide two to three weeks before corn emerges, but with the wet Indiana spring, Krupke says it is already too late for that.
"We don't want producers to have a false sense of security with seed-applied insecticides and some varieties of Bt corn, where the label provides only suppression and not control," Krupke says. "Growers need to check the fine print on the trait they are using. Suppression is fine under ideal environmental conditions and moderate infestation levels, however, under environmental stress and/or heavy pressure, the efficacy of these products labeled for suppression may not be sufficient."
Reduced control efficacy causes struggling seedlings to become more vulnerable to attacks from both above- and below-ground insect pests.
With so little of the state's corn crop in the ground right now, Krupke says it would be awhile before growers start to see black cutworm damage. He encourages scouting fields once crops are planted and determining control strategies as the season progresses.
"We will continue to work with pheromone trap cooperators and to update producers in the coming weeks," he says.
For up-to-date black cutworm scouting and treatment guidelines, watch future issues of the Purdue Pest and Crop Newsletter.