Western bean cutworm in Montgomery Co. corn

Western bean cutworm numbers starting to increase

By Amy Raudenbush, Mark Badertscher, Jordan Beck, Frank Becker, Lee Beers, CCA, Bruce Clevenger, CCA, Sam Custer, Tom Dehaas, Craig Everett, Allen Gahler, Jason Hartschuh, CCA, Andrew Holden, Stephanie Karhoff, Alan Leininger, Ed Lentz, CCA, Rory Lewandowski, CCA, Cecilia Lokai-Minnich, David Marrison, Sarah Noggle, Les Ober, CCA, Eric Richer, CCA, Garth Ruff, Beth Scheckelhoff, Clint Schroeder, Jeff Stachler, Mike Sunderman, Curtis Young, CCA, Chris Zoller, Andy Michel, Kelley Tilmon, Matthew Lorentz, Ohio State University Extension

We are in the third week of monitoring for Western bean cutworm (WBC) in Ohio. Numbers of WBC moths doubled from the previous week; however, overall numbers across the state remain low. Trap counts for the week of July 6 – 12 resulted in a total of 117 WBC adults (1.3 average moths per trap). A total of 27 counties monitored 91 traps across Ohio. Sandusky County reported capturing more than 1 moth per day over the 7-day monitoring period; therefore, scouting for egg masses should begin in this county. Fulton County is approaching scouting threshold. All other counties monitored remain below threshold.

Scouting guidelines

Scout pre-tassel corn approaching tassel fields. Choose at least 20 consecutive plants in 5 random locations (scout different areas of the field that may be in different growth stages). Inspect the uppermost 3 to 4 leaves. Consider treatment if over 8% of inspected plants have eggs or larvae (field corn) or in sweet corn, if over 4% of inspected plants have eggs or larvae (processing market), or >1% of plants (fresh-market).

Western bean cutworm eggs. Photo by OSU Extension.

Treatment

If the number of egg masses/larvae observed exceed threshold, many insecticides are available to adequately control WBC, especially those containing a pyrethroid. However, as with any ear-burrowing caterpillar pest, timing is critical. Insecticide applications must occur after egg hatch, or after tassel emergence, but before caterpillars enter the ear. If eggs have hatched, applications should be made after 95% of the field has tassel. If eggs have not hatched, monitor for the color change. Hatch will occur within 24–48 hours once eggs turn purple. To search for larval injury after it has occurred, search the corn for ears having feeding holes on the outside of the husks.

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