Bean leaf beetles have adapted to Iowa's winters by protecting themselves in leaf litter, but they are still susceptible to cold temperatures. Harsh winters can cause significant mortality. In general, bean leaf beetle adults will die if temperatures fall below -10C. An overwintering model was developed by Lam and Pedigo from Iowa State University in 2000, and is helpful for predicting winter mortality based on accumulating subfreezing temperatures. Figure 1 is a map of predicted mortality in Iowa from the 2009-2010 winter. In general, Iowa experienced very low temperatures, with predicted mortality ranging from 82-99 percent. These numbers are similar to the 2008-2009 winter.