Climatic and Environmental Trends Observed During Epidemic and Non-epidemic Years of Soybean Sudden Death Syndrome in Iowa

Abstract

Soybean yield losses due to sudden death syndrome (SDS) have varied from year to year in Iowa since the disease was first reported in 1993. An SDS epidemic in 2010 resulted in significant yield losses and raised numerous concerns by farmers and agronomists regarding the potential for future outbreaks. Since infection and SDS development is highly dependent on temperature and soil moisture, our hypothesis was that SDS epidemics occur in years with above-average rainfall and below-average temperatures. To test this hypothesis, environmental conditions in southeast and central Iowa were compared among epidemic and non-epidemic years. Mean total precipitation and number of days with precipitation during each month of the growing season (April through August) tended to be greater in epidemic years (10.4 to 26.3 inches, 10 to 15 days) than non-epidemic years (8.9 to 15.4 inches, 9 to 12 days). Soil temperatures in April through July averaged less in epidemic years (9.0 to 24.7°C) than non-epidemic years (10.4 to 26.6°C). The widespread 2010 SDS epidemic in Iowa likely resulted from the concurrence of several weather conditions that were particularly favorable for disease. To reduce risk of yield losses in future years, soybean farmers should use an integrated disease management for SDS, focusing on using resistant varieties, avoiding soil compaction, and avoiding planting in cool wet soils. Accepted for publication 31 January 2013. Published 29 May 2013.