More than 40 years of observations from Ohio confirm the importance of relative humidity and precipitation for Fusarium head blight epidemics

Fusarium head blight (FHB) of wheat, caused by Fusarium graminearum, is a sporadic disease that is dependent, at least in part, on weather and climatic conditions. The goal of this research was to identify environmental variables that are related to FHB over time. For each of 44 years (1965 - 2008), an ordinal assessment of FHB in Ohio was performed, based on the magnitude of disease symptoms, DON in grain, and yield-loss estimates. Weather data were gathered from local weather stations, and summary variables were calculated for a wide range of time windows and starting times of the windows during the wheat growing season. The windows ranged from 10 to 280 days in duration, beginning at June 30 (physiological maturity) and proceeding backwards to September 24 of the previous year (planting time). Based on Spearman rank correlations, FHB was significantly (P < 0.05) associated with average daily relative humidity and total daily precipitation for short- and long- time windows. FHB rating and RH were significantly correlated throughout the growing season, including both early and late spring, but FHB and precipitation were significantly correlated in late spring only. Weather variables that have been identified in this analysis may be used to potentially improve the national FHB forecasting system