New invasive pest threatens corn growers in Pennsylvania

August 12, 2009

A new invasive pest recently found in Pennsylvania could mean serious losses to corn growers in the state.

Western bean cutworm (WBC) was first trapped in July 2009 in Erie and Lycoming counties and has also been found recently in low numbers in Forest, Clarion, Washington, Franklin, and Tioga counties, said John Tooker, assistant professor of entomology at Penn State. "WBC has historically been a pest of corn and dry beans in Great Plains states, but in recent years it has been expanding its range eastward for some unknown reason. This is the first time we've captured WBC in Pennsylvania."

In response to the threat of this invasive pest, 30 pheromone traps were placed across the state in a joint effort of Penn State Cooperative Extension and the Pennsylvania Department of Agriculture. Pheromones are chemicals produced by insects to communicate with other individuals of their species. Pheromone traps can be used by growers to determine the status of pest populations in the field.

According to Tooker, WBC is an important pest of field and sweet corn as well as dried bean crops.

"A heavily infested corn field might have several caterpillars per ear, reducing yields by 30 to 40 percent, so it has the potential to be a severe pest. They have one generation a year and adults are typically active in July, when the adult female moths lay eggs on the upper leaves of corn," he said. "The larvae emerge, feeding on pollen, tassel, and silk tissue on their way to the ear where they feed on developing kernels. Once the pest enters the ear, they are protected from any insecticidal treatment, so it will be important for growers to monitor what is happening in their fields and time management tactics accordingly."

Because the WBC has just been discovered in PA, it may take three to four years for populations to grow and cause serious damage. In the coming years, Tooker plans to expand the trapping program and collect data on where and when the insects are active to help determine the best way to manage the pest.

"We can also look to other states to see how they are managing WBC. There are a number of different insecticides that will help, but treating with insecticides may involve additional expenses because July corn tends to be pretty tall, requiring specialized equipment," Tooker said. "Growers will also have the option of using transgenic technology to combat WBC. Corn varieties with the Bt toxin Cry1F have insecticidal activity against the caterpillars, but growers need to keep in mind that Bt seed is more expensive because they are paying a premium for the new technology."

The pheromone trapping project is a joint effort of Penn State Cooperative Extension, Penn State Department of Entomology, the Crop Management Extension Group and the Pennsylvania Department of Agriculture. Funding for the WBC trapping network was provided in part by Penn State's College of Agricultural Sciences and the Pennsylvania Vegetable Growers Association.

For more information on the cutworm or trapping project, visit online or contact Tooker, by phone at (814) 865-1895 or by e-mail at

Established in 1963, Penn State's Department of Entomology has grown into a well-balanced department providing undergraduate education, graduate student training and extension outreach education focusing on both domestic and international issues. Twenty faculty and more than 40 graduate students work on a variety of research topics providing insights into insect ecology, behavior and molecular biology as well as integrated pest management. The department is part of Penn State's College of Agricultural Sciences. For more information about solving insect problems, descriptions of research and education programs or admission to the graduate program, visit Web site at or contact the department at (814) 865-1895.

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Last Updated August 13, 2009