By Dr. Xianming Chen
November field survey
On Nov. 7, 2017, we were checking winter wheat fields in Whitman, Lincoln, Adams, Grant and Douglas counties in Eastern Washington. We did not see any rust, indicating that the fall infection of winter wheat by the stripe rust pathogen was low. This was different from the high rust incidences observed in many fields in the same regions on Nov. 8, 2016. However, the absence of visible rust in wheat fields before winter is normal for Eastern Washington.
The first forecast for the eastern Pacific Northwest in 2018
Based on the weather conditions in November and December 2017, stripe rust in the 2018 wheat growth season will likely be in the low epidemic level range (0-20 percent yield loss). According to the forecast models based on the November and December weather conditions, highly susceptible winter wheat varieties would have 6% yield loss and currently grown varieties would have less than 3% yield loss. If this forecast is close to the real disease level, the early fungicide application at the time of herbicide application for winter wheat would not be necessary. Based on the past experience, the early prediction made in January is sometimes close to the real situation, but is never better than the prediction in March based on the entire winter weather conditions. Therefore, we will make another prediction in early March.