By Laura Jesse, Plant and Insect Diagnostic Clinic; Erin Hodgson, Department of Entomology; Adam Sisson, Department of Plant Pathology; and Rich Pope, Harrison County Extension Coordinator
The western bean cutworm (WBC), once a pest of the High Plains, has been on the move since at least 2000. (See map below.) This native caterpillar pest of dry beans and corn has been expanding its range to the east through the Corn Belt. WBC spread across Iowa during 2000-2003 and was first recorded in Illinois and Missouri in 2004.
The trapping network expanded in 2005 and WBC moths were recorded in Minnesota and Wisconsin. In 2006 and 2007, WBC was detected further east through Indiana and into Ohio. These appear to be established populations of WBC, but to date reports of economic damage are sporadic.
The reason for this range expansion is unknown but possibilities include reduced tillage not killing overwintering larvae in the soil, climate change, and widespread planting of transgenic corn varieties. There are indications that the use of Cry1Ab corn, which controls European corn borer and corn earworm but not western bean cutworm, may have reduced competition and allowed for greater survival and spread of the western bean cutworm.
Beginning in 2003, Iowa State University set up a network of pheromone traps to monitor WBC range expansion and to provide moth emergence data to enhance scouting efforts. Cooperators included local seed corn dealers, private corn and soybean agronomists and others interested in pest management issues.
The network has expanded with cooperators now in Iowa, Illinois, Indiana, Minnesota, Michigan, Missouri, Ohio, and Wisconsin. Anyone interested in becoming part of the monitoring network should visit the Western Bean Cutworm Monitoring website. The trapping program is explained in detail in the ICM article, Western bean cutworm: Pheromone trapping program.
An article written last summer, Use Treatment Thresholds for Western Bean Cutworm, descripes western bean cutworm, damage and management options.
Western bean cutworm trap catches in the Midwest United States in 2009. In addition to the states shown, adults were captured in Pennsylvania and New York, and in Canada in Ontario and Quebec. (Larger version of this image.)
Description of traps and network
Cooperators construct their own pheromone traps from one-gallon plastic milk jugs. Windows (4-inch squares) are cut in the sides of the jug. A 2-inch space between the window and the bottom of the jug serves as a reservoir that is filled with a 4:1 mixture of water and antifreeze, with a few drops of dish soap. A paper clip, placed inside the jug cap, holds the pheromone lure in place.
All pheromone traps are set up by July 1. Each day, trap cooperators strain the moths out of the solution and count the adult western bean cutworm moths. They then enter the results on a public website.
These trap captures reflect the moth flight within an area and indicate the proper time to start scouting for western bean cutworm eggs.
Laura Jesse is an entomologist with the Iowa State University Extension Plant and Insect Diagnostic Clinic. She can be reached by email at email@example.com or by phone (515) 294-5374. Erin Hodgson is an assistant professor of entomology with extension and research responsibilities. She can be contacted by email at firstname.lastname@example.org or phone (515) 294-2847.