Soybean producers and breeders are constantly striving to increase yields. Over the past decade, soybean diseases have been the primary factors that have most limited soybean yields. For example, estimated yield losses due to Phytophthora stem rot, and pod and stem blight in Iowa in 200 l were 1.8 million pounds each (Wrather et al, 2002). In 2002 in Iowa, 31.5 million pounds of soybeans were lost to foliar disease, and 2.5 million pounds to the stem disease sudden death syndrome (Wrather et al, 2002). Since plant pathogens substantially decrease the yield of crop plants, information on the prevalence and geographic locations of pathogens is useful for prioritizing research to improve disease resistance in breeding programs and to improve integrated disease management programs. During the 2005 growing season, a soybean disease survey was conducted in Iowa. The purpose of the survey was to answer some of the following questions: What foliar, stem and virus diseases of soybean are present in Iowa? What is the prevalence of each disease? What is the incidence of each disease? How does prevalence and incidence of each disease change during the growing season? Therefore, our primary objective was to geospatially map the seasonal changes in the prevalence and incidence of diseases of soybean in Iowa in 2005.