Integrated Crop Management

Western bean cutworm flight starts--early!

Adult western bean cutworms were first collected at two locations in Iowa on June 23--the earliest date they have ever been collected in the state. Single adults were captured in blacklight traps near Correctionville (Woodbury County) in western Iowa and Ames (Story County) in central Iowa. A blacklight trap in Boone County captured 19 adults on June 26. A historical look of western bean cutworm captures for Woodbury County is shown in the table.

Western bean cutworm moth

What these early trap captures suggest is that the moths will be searching for the most mature corn fields in which to lay their eggs. They are attracted to pollinating and silking-stage corn and those fields that are now just beginning to tassel (I have seen one in Story County) should be the most attractive to the adult females. Therefore, any corn that is tasseling during June and is not protected with Herculex® should be closely scouted for western bean cutworm egg masses. According to the University of Nebraska, the economic threshold is eight egg masses per 100 plants.

Thanks to Sara and Ben Linn for operating the blacklight trap and providing the data from Woodbury County.

Five-year blacklight captures of western bean cutworm adults in western Iowa. Woodbury County, 2002-2006.

Western Bean Cutworm Adults
Year First Capture Peak Capture Last Capture Total
2002 June 28 July 13 August 11 12,739
2003 July 10 August 1 August 17 244
2004 July 5 July 23 August 10 531
2005 June 28 July 13 August 11 1,328
2006 June 23 -- -- --

This article originally appeared on page 189 of the IC-496(17) -- June 26, 2006 issue.

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