Don't be surprised to see more bean leaf beetles this season than in typical years. Last year, a large bean leaf beetle population was present in most of Iowa. The mild winter apparently allowed at least 50 percent winter survival of overwintering beetles. This is in contrast to the 25 percent survival recorded last year. The bean leaf beetle completes two generations each year in Iowa. Adults overwinter and emerge in late April or May depending on the temperature. Adults have been reported in 1998 since the third week of April.
Iowa State University
Lam, Wai-Ki Frankie; Krell, Rayda K.; and Pedigo, Larry P., "Early-season bean leaf beetles rarely equal economic damage" (1998). Integrated Crop Management News. 2247.