No. 16 Article 3/July 14, 2006

Western Bean Cutworm Moths Are Being Found in Illinois Traps

A network of pheromone traps to monitor for western bean cutworm moths was established throughout Illinois in late June and early July. The widespread network (across essentially every county) should help us determine the 2006 distribution of this potentially threatening pest, which had not been found in Illinois before 2004. Trap operators in a few locations in Illinois already have reported captures of western bean cutworm moths. You can view trap captures thus far at the Iowa State University "Western Bean Cutworm Monitoring Network" Web site.

Unfortunately, operators may have to be more careful when identifying moths captured in the pheromone traps. Although the pheromone is supposed to be specific for western bean cutworm, trap operators in Illinois have been finding other species of moths in the traps with some frequency. Kelly Cook, entomologist with the Illinois Natural History Survey and coordinator for the western bean cutworm trapping effort, has received several phone calls and e-mail messages indicating that other species of moths are being captured in the western bean cutworm traps. Although western bean cutworm moths have characteristic markings on their wings, they could be confused with other species of moths.

The western bean cutworm moth is brown, gray, and cream-colored with a broad pale stripe along the front edge of the forewing. In addition, there are two distinctive spots--a circle and a "boomerang"--on the forewings. Other species of moths lack these characteristic markings.

Check out the fantastic photograph sent to us by Jim Donnelly, Crops Specialist with Ag View FS in Bureau County. The wing characteristics previously descried are quite clear. Jim found the western bean cutworm moth resting in a soybean field, and the moth graciously posed for the photo.

Western bean cutworm moth, Bureau County, Illinois, July 2006 (photo courtesy of Jim Donnelly, Ag View FS).

To compare a western bean cutworm moth with other species, check out the photos posted on the University of Nebraska South Central Agricultural Laboratory Web site; click on "Moths." In our opinion, the dingy cutworm moth may be the species most easily confused with western bean cutworm moths. However, some trap operators in Illinois have captured yellowstriped armyworm moths, which also resemble western bean cutworm moths in some ways. The army cutworm is also a candidate for confusion with the western bean cutworm.

The occurrence of the western bean cutworm in many northern Illinois counties in 2005 raised the level of concern among corn growers about this insect. Although we do not believe the western bean cutworm has achieved pest status in corn in Illinois yet, it's probably only a matter of time before corn growers must consider the insect's management. Accurate identification of the pest is thus extremely important. We hope you find the identification aids useful.--Kevin Steffey and Kelly Cook

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