2017 wheat stripe rust predicted on 'epidemic' level

The prediction for damage from stripe rust has been set at “severe” for this year, according to a forecast from the WSU Wheat and Small Grains division.

Dr. Xianming Chen, USDA-ARS Research Plant Pathologist in Pullman, released his most recent prediction March 6. The forecast was based off six different models based on air temperature. While temperatures did drop below five degrees several times – the threshold for fungus survival – the long-standing snow cover protected the wheat and fungus.

Field observations show the stripe rust survived the winter. Chen stated stripe could “cause yield loss of 32 percent on highly susceptible varieties.” This compares the Chen’s earlier prediction in January when the forecast was for only six percent loss.

Actively sporulating stripe rust pustules were found the week of March 6 in Walla Walla County where the wheat was starting to grow. In his forecast, Chen reported finding stripe rust pustules in a field just south of Odessa in Lincoln County.

“Please keep in mind that even one pustule of stripe rust in a field grown with a susceptible cultivar in the early spring can cause epidemic in the growing season if later on the weather conditions are favorable to the disease,” Chen stated in his forecast. Weather conditions are favorable with the excess moisture which is expected to last into the late spring and early summer.

Winter wheat should be checked just before herbicide application. If the variety of wheat is moderately susceptible or stripe rust is found, Chen recommends applying a fungicide at the same time. A second application may be needed around the flag leaf stage, depending on various factors. If planting spring wheat, farmers are urged to consider stripe rust resistant varieties.

Chen’s forecast also noted stripe rust has been found in Texas, Louisiana, Mississippi, Arkansas and North Carolina. The disease is expected to develop into “severe and widespread epidemic throughout the Great Plains and further into east regions” unless there is drought.