By John Tooker
The Threat, Though Low, Remains in the Northern Counties
As in previous years, this summer Penn State Extension, in collaboration the Department of Entomology, is trapping for western bean cutworm. We have had pheromone traps deployed since mid-June in 21 counties to search for moths of this species. This potential pest of corn and dry and snap beans was found for the first time in Pennsylvania in 2009 when we found less than hundred moths distributed across the state. In the years since 2009, we have had a mild population in Pennsylvania with the number of moths that we have captured annually staying around 350, with most moths being found in the northern tier of counties. These populations are quite low compared to populations discovered in NY, MI, OH, WI, and Ontario, where this pest has caused economic damage.
In Pennsylvania, to date, we have only confirmed the presence of larvae in one corn field in Centre County, though a few fields in Potter County have been suspect. Most importantly, we have seen no economic damage. Nevertheless, we continue to tracks western bean cutworm populations in Pennsylvania to characterize the threat in our fields.
So far this year, we have captured about 300 moths with most being found in Centre, Elk, and Bradford Counties. I encourage folks to be on the lookout for these caterpillars in their corn fields. The caterpillars looks similar to corn earworm, but does not have lines down the sides of its body like corn earworm does and has three distinct light-brown lines on its “neck” just behind its head (Figure 1).
Figure 1 Western Bean Cutworm larvae. Photo by Eric Bohnenblust