Soybean aphid experience in Iowa: Like most of the Midwest, Iowa soybean growers were introduced to a new pest when the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), arrived in 2000. And like many other states, Iowa has experienced large populations of aphids (>2,000/plant) in two of the past five years that the aphid has been in the state (Lang 2003, M. O'Neal unpublished). Although not well understood, there is an apparent oscillation in aphid populations between years with large populations occurring in 2001 and 2003, and low populations (<500 aphids per plant) occurring in 2002 and 2004.