The spring migratory flight of black cutworm moths remained impressive across Illinois and the Corn Belt through mid-April according to University of Illinois Professor of Entomology and Crop Sciences Extension Coordinator Mike Gray. Dale Baird, University of Illinois Extension, reported capturing 23 moths in his pheromone trap over a two-day period (April 14-15) in northern Illinois (Lee County), well above the intense capture threshold of nine or more moths over a one- to two-day time frame. On April 15, Jim Morrison, a cooperator with the Insect Monitoring Program also reported capturing 11 moths in one of his northern Illinois traps.

"Corn plants in the one- to four-leaf stage remain susceptible to cutting, and producers should be monitoring their fields closely this spring for potential stand reductions," Gray says.

Time spent scouting for signs of trouble could be time well spent this year. "Don't take for granted that a Bt hybrid will provide adequate protection against large infestations of this insect pest," Gray reminds readers.

Recently, some below-freezing temperatures settled in across much of central and northern Illinois, leading growers to hope that the cold would reduce the populations of black cutworms and other insects. Unfortunately, insect pests are able to move to more protected areas (below ground burrows, beneath plant debris) and escape the freezing temperatures.

In his 2007 article (Black cutworms and the hard freeze), Marlin Rice, a longtime extension entomologist with Iowa State University and now with Pioneer Hi-Bred International Inc., observed that eight hours of freezing temperatures, with a low of 19° F, appeared to have no effect on the survival of the black cutworm eggs and subsequent larval hatch. The article is available online.

"The key take-home message," says Gray, "is don't assume that the cold weather has taken care of the black cutworm threat this spring. Farmers will need to remain vigilant."