Late Planting Could Increase Corn’s Susceptibility to Black Cutworm

05:22PM Apr 26, 2018
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Corn has enough challenges this season thanks to delayed planting—don’t let black cutworms (BCW) steal more yield. With each bite they take, stands are reduced and yield is limited before the crop even sets an ear.

“We expect [BCW] activity to increase over the coming weeks,” says Kelley Estes, University of Illinois entomologist. “As both corn and soybean planting progress, we encourage growers to scout emerging fields for the presence of insect injury.”

The insect flies in from the south, so southern fields could see the effect of BCW sooner than northern fields. In addition, fields with weeds, cover crops or trash could provide ideal habitat for moths to lay eggs—so be especially mindful of their threat in those fields.

“Don’t assume ‘I planted a Bt hybrid, I don’t need to worry about this pest,’” says Michael Gray, University of Illinois professor emeritus. “Not all Bt hybrids offer the same level of protection. If it just offers suppression, scout more diligently.”

Corn is at the greatest risk when it’s less than 15” and stand loss is potentially greater when the growing point is above the ground. If BCW cuts the plant off at the base but the growing point is below ground the crop might be able to recover. Consider rescue treatment if 3% of the stand has BCW cutting damage, but know damage can appear in the form of small pinholes on the leaves, too.

BCW started flying northward from Gulf States in March, and farmers should scout for the pest through May. Cuttings typically occur during long nights or dark, overcast days.

Experts offer farmers a few tips while scouting:

  • Look for early signs of leaf feeding, such as pinholes in leaves, as a potential indicator of cutting rather than wait to treat after cutting takes place
  • Plants in the one- to four-leaf stage are most susceptible to cutting and will suffer the greatest economic damage
  • Late tillage and planting increases the susceptibility of fields to BCW
  • A single cutworm will cut three to four plants
  • There are three to four BCW generations each year
  • Fields planted after soybeans or winter wheat are more likely to have BCW

Take a close look at your trait packages, seed treatments and insecticide plans. Are you prepared to manage a potentially larger risk of BCW? If not, create a contingency plan so you’re one step ahead of this troublesome pest.