Issue No. 3, Article 2/April 20, 2012
Black Cutworm Moth Flights Remain Intense--Freezing Temperatures Have Minimal Effect on Potential Cutting Threat
The spring migratory flight of black cutworm moths remained impressive across the state through mid-April. Dale Baird, University of Illinois Extension, reported capturing 23 moths in his pheromone trap over 2 days (April 14-15) in northern Illinois (Lee County), well above the intense capture threshold of 9 or more moths over 1 to 2 days. Jim Morrison, a cooperator with the Insect Monitoring Program, also reported capturing 11 moths (April 15) in one of his northern Illinois traps.
Corn plants in the 1- to 4-leaf stage remain susceptible to cutting, and producers should be monitoring their fields closely for potential stand reductions. The flight of black cutworm moths this year has been strong and covers a large swath of the Corn Belt. Scouting for signs of trouble could be time well spent. As mentioned previously in the Bulletin, don't take for granted that a Bt hybrid will provide adequate protection against large infestations of this pest.
Recently, below-freezing temperatures settled in across much of central and northern Illinois. Not surprisingly, many questions surfaced about the impact on black cutworms and other insects. In general, insects can move to more protected areas (below-ground burrows, beneath plant debris) and escape the freezing temperatures. Corn seedlings in some fields have been less fortunate.
Dr. Marlin Rice, a long-time extension entomologist with Iowa State University now with Pioneer Hi-Bred International, shed some light on this topic in 2007 (Black cutworms and the hard freeze). He constructed a simple but informative experiment and made the following observation: "The 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." I encourage you to read the full article, published in Iowa State's Integrated Crop Management Newsletter on April 16, 2007. The key take-home message? Don't assume that the cold weather has taken care of the black cutworm threat this spring. Producers need to remain vigilant.--Mike Gray