New invasive pest threatens corn growers in Pennsylvania


UNIVERSITY PARK, Pa. — A new invasive pest recently found in Pennsylvania could mean serious losses to corn growers in the state.

Western bean cutworm 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.

“Western bean cutworm 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 Western bean cutworm in Pennsylvania,” explained Tooker.

Pheromone traps

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, Western bean cutworm 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 explained.

“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 Western bean cutworm has just been discovered in Pennsylvania, it may take three to four years for populations to grow and cause serious damage.

Expand trapping program

In the coming years, Tooker plans to expand the trapping program and collect data on where and when Western bean cutworm is active to help determine the best way to manage the pest.

“We can also look to other states to see how they are managing Western bean cutworm. There are a number of different insecticides that will help; however, treating with insecticides may involve additional expenses because July corn tends to be pretty tall, requiring specialized equipment,” said Tooker.

“Growers will also have the option of using transgenic technology to combat Western bean cutworm. 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.”

Joint effort

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 Western bean cutworm trapping network was provided in part by Penn State’s College of Agricultural Sciences and the Pennsylvania Vegetable Growers Association.

More information

For more information on the cutworm or trapping project, go to, call Tooker at 814-865-1895 or e-mail

Get our Top Stories in Your Inbox

Next step: Check your inbox to confirm your subscription.



We are glad you have chosen to leave a comment. Please keep in mind that comments are moderated according to our comment policy.

Receive emails as this discussion progresses.