Western bean cutworms continue to be a concern, especially in western Iowa. Joel DeJong, Iowa State University Extension field specialist-crops, reports fields above the economic threshold of eight egg masses per 100 plants in Cherokee, O'Brien, and Woodbury counties. The highest egg count was 20 egg masses per 100 plants. Nightly catches in a blacklight trap north of Correctionville have dropped from the peak on July 13 but still remained high (more than 500 per night) through July 21. Moths have been caught in traps in northeastern Iowa (Butler County), and I have found them in central Iowa (Story County). Therefore, I would expect the damage from this insect to occur in areas where corn producers have not traditionally seen this pest. Unless fields are scouted now (or even better, last week), many corn producers may be surprised at the ear damage from western bean cutworms during harvest.
Many thanks to Sara and Ben Linn for operating the light trap in western Iowa. Their diligence in counting thousands of moths is greatly appreciated.
Nightly trap catches of western bean cutworm moths near Correctionville, Woodbury County, June 28-July 22.
This article originally appeared on page 157 of the IC-488(19) -- July 29, 2002 issue.