Penn State Resumes Monitoring of Western Bean Cutworm

By Blake Jackson

Western bean cutworm (WBC) continues to be a puzzling insect for both researchers and corn producers in Pennsylvania. This pest lays eggs throughout June, July, and August, and its larvae feed on corn’s reproductive structures, particularly tassels and developing ears.

While long known as a major concern for growers in Nebraska and other western states, WBC began spreading eastward in the early 2000s, raising concerns for the Mid-Atlantic region.

In Pennsylvania, pheromone trapping first confirmed WBC moths in 2009. From then until 2015, annual monitoring was conducted, but the effort was discontinued in 2016 after failing to detect significant larval infestations in cornfields.

At the same time, surrounding states such as New York, Ohio, Michigan, and Wisconsin, along with Ontario, were experiencing large moth populations and consistent crop damage, particularly in corn, dry beans, and snap beans.

This summer, in 2025, Penn State Extension resumed WBC monitoring to determine whether the pest had become more abundant and if caterpillar infestations could now be found.

Extension educators set pheromone traps across ten counties in July and August, reporting results to the Great Lakes and Maritimes Pest Monitoring Network, which is coordinated by Ontario’s Ministry of Agriculture, Food and Rural Affairs.

While moths were captured during the season, the numbers were far lower than those observed in nearby states and Ontario, and no infested fields have yet been confirmed in Pennsylvania.

As harvest season approaches, Penn State researchers are encouraging growers and crop scouts to check corn ears closely for WBC caterpillars.

If infestations are observed, reporting these findings to local agronomy educators or Penn State Extension would provide valuable insight.

For identification, WBC caterpillars can be distinguished from similar pests such as corn earworm and fall armyworm. Unlike these species, WBC larvae lack side stripes and instead display three light-brown lines on the “neck” area just behind the head. Continued monitoring and farmer feedback will be essential to determine whether WBC represents a real threat to Pennsylvania’s corn production moving forward.

Photo Credit: gettyimages-songdech17