Iowa soybean farmers have not had to contend with high populations of overwintered bean leaf beetles during the past two years, but that may be about to change. Samples taken from Iowa State University research farms near Ames indicate the beetle populations are higher now than during the past two years. Beetle populations averaged 75 beetles per 50 sweeps last week. This year's population is approximately three times larger than the 2004 population and nine times larger than the 2003 population, when sampled during the same week in May (see Figure 1). Fortunately, the population is nowhere near the size of the record-setting beetle counts we collected in 2002.
Emerged soybeans, and especially those near wooded areas, should be scouted now for this insect. See the May 2, 2005, ICM Newsletter for information on scouting and economic thresholds for this insect.
This article originally appeared on page Page 2 of the IC-494(11) -- May 23, 2005 issue.