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.

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.