By Dr. Xianming Chen
Based on the weather conditions in November and December 2020, stripe rust in the 2021 wheat growing season is forecasted to be in the upper range of moderate epidemic level (20-40 percent yield loss on susceptible varieties).
Using forecast models based on the 2020 November and December weather data, yield loss of highly susceptible winter wheat varieties in the 2021 crop season is forecasted to be in the range of 27 to 46 percent with an average of 39 percent. This number is lower than the forecast (44 percent) made last January for the 2020 crop season due to the relatively cold weather of December in 2020 compared to 2019. Currently grown varieties are forecasted to be 0 to 29 percent yield losses depending upon the level of resistance or susceptibility of individual varieties. Based on the forecast, fields grown with moderate susceptible or susceptible winter wheat varieties (stripe rust ratings 5 to 9) may need the early fungicide application at the time of herbicide application.
The early prediction made in January is often close to the real situation, but usually not better than the prediction in March based on the entire winter weather. Therefore, we will make another prediction in early March. However, stripe rust resistant or moderately resistant spring wheat varieties (stripe rust ratings 1 to 4 in the Seed Buying Guide) are recommended for planting.