Refinement of Field Scouting for Western Bean Cutworm with a Cooperative, Four-State Trapping Network

Marlin Rice, Faculty, Entomology
(collaborators include Richard Pope (primary lead), Carol Pilcher, John VanDyk, Kevin Steffey (University of Illinois), and Brent Wilson and Scott DeJong (Pioneer Hi-Bred International).


The western bean cutworm is an insect pest of corn that emerged as an economic pest in west-central Iowa in the last decade. Since then, it has been observed in cornfields in central Iowa and last year was found in eastern Illinois along the Mississippi River.  Western bean cutworm is difficult to manage with conventional insecticides because adult flight, egg laying, and larval entry into corn ears occurs over a 5-6 week period in July and early August. When larvae enter corn ears their feeding can cause severe economic damage to developing kernels.  Some producers have reported up to 40% yield reductions, but damage can vary greatly from field to field.  The window of opportunity for insecticide treatment is narrow, usually 7 to 10 days, starting with egg hatch and ending when the larvae enter the ears.  Field scouting can be more critically timed if adult moth flight is known for a given area.

Three key issues need to be addressed concerning integrated pest management of western bean cutworm in Iowa and neighboring states: 1) knowledge of the local presence of cutworm populations, 2) factors that affect western bean cutworm infestation in corn, and 3) the timing of adult emergence and subsequent oviposition on corn.  Pheromone traps are useful tools for monitoring emergence of WBC, and emergence patterns can be followed to focus scouting of fields. 

We recruited a network of volunteer agriculturalists to establish and monitor traps during July and August. These volunteers posted trap-capture data to a website at  This  website was made public and promoted through the ISU Integrated Crop Management newsletter, as a Partnership Perk (an expedited e-mail notice to the Corn and Soybean Initiative partners), through a news release from ISU Communications, and in live radio broadcasts.
We cooperated with Pioneer Hi-Bred International and our ISU Field Crop Specialists for trap locations in Iowa and Missouri. Additionally, Kevin Steffey, University of Illinois, recruited cooperators that used our protocol and posted to the ISU website, and the University of Minnesota posted data gathered from 6 light-trap locations in southern Minnesota. 
In total, there were 198 reporting traps placed in 116 counties in Iowa, Illinois, Missouri, and Minnesota. The traps and counties covered by state were:
                        State                trap locations                counties
                        Iowa                       141                            79
                        Illinois                        43                            34
                        Missouri                     8                               7
                        Minnesota                  6                               6                          

Western bean cutworm known presence: From this years trap network, we expanded the known range of western bean cutworm throughout Iowa, east to Will County Illinois on the Indiana border, and south to Montgomery County Illinois, near Terra Haute, IN.  An image of the trap captures through July 20 is shown on the last page of this report.  Also, large regional populations were identified in Benton, Buchanan, Delaware, Jones, and Linn counties in Iowa that were previously not clearly known. 
In late August we sent an e-mail survey to our trap cooperators asking them several questions about how they used the data, its value to them, and what if any suggestions they have for future work with western bean cutworm. The following responses address both the dissemination of information to producers, and highlight some of the needs for future research on WBC.

Other comments volunteered by the survey respondents are listed here:

142 -- Integrated Pest Management/Integrated Crops Management

Page last updated: July 9, 2006
Page maintained by Linda Schultz,