The first-generation of the bean leaf beetle can now be found across Iowa. These beetles developed from eggs that were laid by overwintered beetles on seedling soybean during May and early June. The highest numbers reported so far are from John Holmes, extension field specialist in crops, in Webster County. Using a sweep net, he collected from 20 to 138 beetles per 10 sweeps and averaged 63 beetles per 10 sweeps. This field was planted on April 20 so it is really not surprising that beetle counts are extremely high. Early-planted fields always attract the most overwintered bean leaf beetles, thereby creating repetitive problems from the first and second generations during the growing season. All soybean fields should be scouted now. See the July 16, 2001, ICM article  for detailed information on scouting and economic thresholds for the first-generation bean leaf beetles.
This article originally appeared on page 161 of the IC-486(20) -- July 30, 2001 issue.