Effect of agronomic practices on sudden death syndrome of soybean in Iowa

Abstract

Sudden death syndrome (SDS) caused by the pathogen Fusarium virguliforme is a disease in Iowa causing significant yield reductions in soybean [Glycine max (L.) Merr.]. Research in the southern United States has demonstrated that early-planted soybean exhibits more severe SDS symptoms than late-planted soybean. The objective of this study was to evaluate the effect of planting date on SDS foliar symptom incidence, severity and yield in Iowa. In 2008 and 2009, a SDS-susceptible and SDS-resistant cultivar were planted at two Iowa locations at three different planting dates in plots inoculated with and without the pathogen. Beginning at first demonstration of foliar symptoms, plots were visually assessed every ten days for disease incidence and severity. Weather conditions varied across years, resulting in inconsistent and low disease levels. Planting date had an effect on SDS disease expression with early-planted soybean demonstrating higher occurrence of SDS than lateplanted soybean. Despite higher levels of disease with early-planted soybean, yield was not less than late-planted soybean. The SDS-susceptible cultivar yielded higher than the SDSresistant cultivar in both years, despite higher levels of disease, particularly in 2009. Although disease expression was greater in early-planted versus late-planted soybean it is