Western Bean Cutworm Information

Western Bean Cutworm: A new insect pest threatens Pennsylvania corn fields
John Tooker

Western bean cutworm (WBC; Noctuidae: Striacosta albicosta) is a pest of corn (field corn, sweet corn, and popcorn) that has recently arrived in Pennsylvania.  Historically, it has been a pest of corn and dry beans in the Great Plains; however, for some unidentified reason it has been moving eastward. In 2000, it was detected in northwestern Iowa and by 2004 had reached southeastern Iowa and threatened the western edge of Illinois. It was detected in Indiana in 2005 and Wisconsin, Michigan, and Ohio in 2006.  In 2008, it had moved farther east, colonizing Ontario and central Ohio. In 2009 & 2010, Penn State established a monitoring network for western bean cutworm, and we will also trap for the moth in 2011 (see below for more information).

Adult moths can be monitored with pheromone traps, and they look similar to other noctuid moths (see this Iowa State webpage for a comparison of similar looking species: http://www.ipm.iastate.edu/ipm/icm/2007/6-11/wbc.html).  Western bean cutworm moths are distinct because of three features on their forewings.  No other moths in Pennsylvania have these three features: 1) the broad white band on the leading edge of their forewing; 2) a white "period" and 3) a crescent-shaped "comma," both adjacent to the white band (Fig. 1).

Fig. 1. Distinctive forewing of western bean cutworm.

Western bean cutworm completes a single generation per year. Adult moths fly in mid-summer and females lay eggs on the upper surfaces of corn leaves. As a late-season corn pest, WBC larvae feed on tassels, silks, and developing kernels and can cause severe damage. Chemical control can be a challenge because larvae spend considerable time inside the husk.  Some transgenic corn varieties have activity against western bean cutworm caterpillars.

To track the population as it enters and spreads across Pennsylvania, we have been monitoring moths with pheromone traps.  We trapped for the 2009 & 2010 growing season, and our effort is underway for 2011.  See links below for trapping details and results.   Our trapping network is a joint effort between the Department of Entomology and Penn State Extension.  Traps in Pennsylvania are being checked and maintained by Penn State county-based extension educators.  In the first two years of trapping we were also joined by Pennsylvania Department of Agriculture (PDA).

2012 Trapping Progress for Pennsylvania

2011 Trapping Progress for Pennsylvania

2010 Trapping Progress for Pennsylvania

Trapping efforts in nearby states and Ontario:
Ohio: http://entomology.osu.edu/ag/pageview3.asp?id=1390

Michigan:http://www.ipm.msu.edu/cat09field/8-12WBCmap.pdf