The flight of the western bean cutworm is coming to an early close this year. Blacklight trap captures from both Boone and Woodbury counties indicate that the populations peaked on July 5 and July 9, respectively (see figures). The historical data from Woodbury County indicates that the flight started six days earlier, and peaked six days earlier, than it had any previous year in western Iowa. It appears that the flight will end considerably earlier; maybe by as much as 10 to 14 days.

What these flight data suggest is that field scouting decisions should have been made last week to coincide with peak egg laying and hatching activity. Insecticides applied this week may still kill eggs and newly hatched larvae, but the proportion of the population controlled will be relatively small compared to the overall population within the field. The best time for control of the western bean cutworm has come and gone for 2007.

Six-year blacklight captures of western bean cutworm adults from Woodbury Co., Iowa, 2002-2007.

*Through July 23, 2007

Adult western bean cutworm captures in a blacklight trap, Boone Co., Iowa, 2007. Peak capture on July 5.

Adult western bean cutworm captures in a blacklight trap, Woodbury Co., Iowa, 2007. Peak capture on July 9.