Risk assessment models for wheat Fusarium head blight epidemics based on within-season weather data

Logistic regression models for wheat Fusarium head blight were developed Using information collected at 50 location-years, including four states, representing three different U.S. wheat-production regions. Non analysis parametric correlation analysis and stepwise logistic regression identified combinations of temperature, relative humidity, and rainfall or durations of specified weather conditions, for 7 days prior to anthesis. and 10 days beginning at crop anthesis, as potential predictor variables. Prediction accuracy of developed logistic regression models ranged from 62 to 85%. Models suitable for application as a disease warning system were identified based on model prediction accuracy, sensitivity, specificity, and availability of weather variables at crop anthesis. Four of the identified models correctly classified 84% of the 50 location-years. A fifth model that used only pre-anthesis, weather conditions correctly classified 70% of the location-years. The most useful predictor variables were the duration (h) of precipitation 7 days prior to anthesis, duration (h) that temperature was between 15 and 30degreesC 7 days prior to anthesis, and the duration (h) that temperature was between 15 and 30degreesC and relative humidity was greater than or equal to 90%. When model performance was evaluated with an independent validation set (n = 9) prediction accuracy was only 6% lower than the accuracy for the original data sets. These results indicate that narrow time periods around crop anthesis can be used to predict Fusarium head blight epidemics.