WAWG
Stripe rust developing on spring wheat, barley crops
By Xianming Chen
Plant Pathologist, USDA-ARS
Based on recent field surveys in Adams and Whitman counties of Washington, wheat crops have been progressing fast since the last update in May. Winter wheat ranged from Feekes 10.5.4 (milk) to Feekes 11.3 (almost ripe). Spring wheat ranged from Feekes 5 (early jointing) to Feekes 10.5.3 (flowering completed), and spring barley ranged from Feekes 10 (boot) to Feekes 10.5.3 (flowering completed). The hot weather from June 4 to June 8 pushed crops to grow and mature faster. Winter wheat harvesting is expected at least two weeks earlier than normal.
The hot period slowed stripe rust little bit but did not completely stop the disease. As the winter crop is maturing, the rust season on winter wheat in most of the Pacific Northwest is over, and the disease is pretty much under control. However, stripe rust is developing on spring wheat. As the weather has been much cooler with some moisture, new and active stripe rust pustules were seen in several commercial fields of spring wheat, although incidence and severity were generally low. In our experimental fields at Lind (Adams County) where wheat plants were at the flowering to milk stages, susceptible spring wheat varieties had up to 80 percent severity. Such severe rust is not common for this dryland location. In our nurseries at Pullman (Whitman County), spring wheat plants were at early jointing (Feekes 5) to late jointing (Feekes 8) stages, and stripe rust was very severe on susceptible varieties with 100 percent incidence and more than 80 percent severity on lower leaves.
For fields of susceptible and moderately susceptible spring wheat varieties, fungicide application is needed. If a fungicide was applied more than three weeks ago or active rust pustules start showing up, consider a second application.
Stripe rust of barley
Stripe rust was found on spring barley in commercial and experimental fields. In our experimental field at Lind, stripe rust up to 30 percent severity was observed on susceptible varieties. In two commercial barley fields at heading stage, stripe rust was found at less than 1 percent severity or incidence. Up to 5 percent incidence was found in our experimental fields near Pullman. Early this week, a sample of barley plants received by the disease diagnostic lab had 10 to 30 percent severity. Compared to wheat stripe rust, barley stripe rust pressure is relatively low, and fungicide application is generally not needed. However, in fields of highly susceptible barley varieties under irrigation or in areas that have had significantly high moisture, stripe rust can develop to significant levels. Please check your fields, if rust incidence reaches 5 percent, consider a fungicide application.
Stripe rust in the U.S. and Canada
Since the last update, stripe rust of wheat has been reported in Wyoming and New York. Thus, stripe rust has been reported in 31 states: Texas, Oregon, Louisiana, Arkansas, Oklahoma, Washington, Colorado, Kansas, Mississippi, Georgia, California, Virginia, Montana, Indiana, Idaho, North Carolina, Tennessee, South Dakota, Kentucky, Illinois, Nebraska, Minnesota, Delaware, Florida, Michigan, Ohio, Wisconsin, Utah, North Dakota, Wyoming and New York. Stripe rust has also reported in Alberta, Ontario and Manitoba provinces of Canada.