Stripe Rust Update, June 11, 2015

Xianming Chen

Stripe rust in eastern Washington

We were checking wheat and barley fields in eastern Washington yesterday and today.  Winter wheat ranged from flowering (Feekes 10.5) to dough stage (Feekes 11), and spring wheat ranged from early jointing (Feekes 5) to flowering stage.  In our experimental nurseries at the Lind Dryland Station (Adams County), stripe rust was low (up to 5% incidence and 2% severity) on susceptible varieties of winter wheat and relatively high (up to 10% incidence and 15% severity) on susceptible varieties of spring wheat.  In our experimental nurseries around Pullman (Whitman County) without inoculation, stripe rust developed up to 100% incidence and 100% severity on susceptible varieties, indicating a severe epidemic level.

In commercial fields, stripe rust were found in many fields of both winter wheat and spring wheat, but generally at low levels.  Compared to the last report on May 21, stripe rust has not developed much on winter wheat.  The major change is the presence of stripe rust in spring wheat fields.  In general, stripe rust is more in the Palouse region in the eastern side and less towards the central part of the state due to the moisture differences.  Compared to the severe stripe rust in experimental nurseries, the relatively low levels in commercial fields were due to 1) resistant varieties, 2) early application of fungicides at the time of herbicide application, and 3) the relatively dry conditions since April.

The management of stripe rust is basically over for winter wheat.  Rust is expected to develop little bit more over the next week in fields of late winter wheat crop in the areas where some precipitation occurred in the early June, but should not cause significant yield loss.  For spring wheat, the stripe rust management is not over.  If a field was sprayed with a fungicide at the time of herbicide application, no further fungicide application is needed.  If fields planted with susceptible spring varieties still have good soil moisture and has not been sprayed with fungicides, fungicide may be needed before flowering, especially in the Palouse region and further north and east in the high elevation areas.  Please check spring wheat fields for any rust development, and consider spray if active rust is observed.

Barley stripe rust was observed only in our experiment fields.  Fungicides are not needed for commercial barley fields.

Stripe rust in the country

So far, stripe rust of wheat has been reported in 26 states, including Oregon, Louisiana, Texas, Arkansas, Mississippi, Oklahoma, Washington, California, Montana, Arizona, Colorado, Kansas, Nebraska, Tennessee, Georgia, Utah, Idaho, Virginia, Illinois, Indiana, South Dakota, North Dakota, Wisconsin, Minnesota, Wyoming, and Michigan.  Severe stripe rust have recently damaged wheat crops in Nebraska and Colorado.   This is a year of widespread stripe rust in the country.