No. 12 Article 2/June 15, 2007

Accurate Identification of Western Bean Cutworm Moths Is Crucial

Western bean cutworms are recent invaders of Illinois corn fields (first found in 2004), and the increase in captures of western bean cutworm moths in pheromone traps from 2005 to 2006 has corn growers aware, at the very least, of their presence. In addition, there were reports of injury to corn ears in some northern Illinois counties in 2006, so many people will be on alert for this pest in 2007. As part of the "alert system," University of Illinois Extension educators have erected pheromone traps in several areas of the state so that we can watch for and report first and peak captures, with peak captures being triggers for field scouting. We are also aware that personnel with Pioneer Hi-Bred International will have a network of traps, and other organizations and individuals also may be monitoring for western bean cutworm moths with pheromone traps. Much of the information will be submitted to Iowa State University's Western Bean Cutworm Monitoring Network.


Western bean cutworm pheromone trap (photo courtesy of Marlin Rice, Iowa State University).


Western bean cutworm adult (photo courtesy of Jim Donnelly, Ag View FS).

Most pheromone traps for monitoring for western bean cutworm moths should be in place throughout Illinois and the rest of the Midwest by mid-June. However, some folks got a jump on things and have already set up their traps. And, believe it or not, some people have already reported captures of moths in the traps--but not western bean cutworm moths. This is a crucial issue, so we want to emphasize the importance of accurate identification of western bean cutworm moths to avoid "inflation" of the database.

We first became aware of the possibility of capturing moths other than western bean cutworm moths in western bean cutworm pheromone traps last year and reported this situation in issue no. 16 of the Bulletin. The species most often misidentified as western bean cutworm was the yellowstriped armyworm. In the June 8, 2007, issue of the University of Minnesota's Minnesota Fruit and Vegetable IPM News, Eric Burkness and Bill Hutchison wrote an article regarding captures of moths other than western bean cutworm moths in pheromone traps that are supposed to capture only western bean cutworms. They, too, suspect that the species being captured was the yellowstriped armyworm.

I encourage anyone interested in western bean cutworm to access the "videos" (audio recordings synchronized with PowerPoint slides) for the western bean cutworm short course delivered on February 28, 2007. The videos are located on the North Central IPM Center Web site. The video titled "Look-Alikes . . ." by Marlin Rice, extension entomologist at Iowa State University, provides a terrific overview of identification characteristics of both larvae and adults of western bean cutworms and look-alike species. Again, I emphasize the importance of accurate identification of western bean cutworms.

On a related note, we promised to publish answers to questions submitted to us after the conclusion of the short course. Although it has taken us a while to answer them all, we finally have done so; the questions and answers are also at the North Central IPM Center Web site. Several answers to the questions we received should offer additional insight about western bean cutworms, so we invite your access.--Kevin Steffey

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