During the last 20 years, the bean leaf beetle has undergone tremendous population changes in Iowa. From 1989 to 1996, the populations (both first generation and second generation) were relatively insignificant and the insect was not considered to be a serious pest. But in 1997, the population in central Iowa began a yearly escalation until it reached a historical high in 2002. Populations that year were nearly 400 times larger than those of the mid-1990s and we believe that this was due in part to milder winters followed by earlier planting of soybeans. Since that time, the population has returned to more normal levels and is similar to what we witnessed at the beginning of the beetle explosion in the late 1990s.