Some locations in Iowa have many bean leaf beetles this year. After a large population of overwintering beetles, the first generation beetles are now emerging, with as many as 147 beetles in 20 sweeps from a field in Ames. Without careful attention, these beetles can be confused with other economically important beetles found in soybean. A few spotted beetles currently can be found in soybean, such as the twelvespotted lady beetle, Coleomegilla maculata; the multicolored Asian lady beetle, Harmonia axyridis; and spotted cucumber beetle, Diabrotica undecimpunctata. Photos of the lady beetles can be found at http://www.ipm.iastate.edu/ipm/icm/2002/5-20-2002/ladybean.html 
|Several color phases of the bean leaf beetle.|
Bean leaf beetles typically are yellow and usually can be distinguished by four quadrangular, black marks on their wing covers. However, these beetles frequently are without markings on the wing covers and range from red to yellow. The most reliable character is a small, black triangle between the "neck" and wing covers. This marking is always present and distinguishs the bean leaf beetle from other beetles in soybean.
This article originally appeared on page 159 of the IC-488(19) -- July 29, 2002 issue.