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Stripe Rust Update June 25 2015

By Xianming Chen
Stripe rust in Washington

Based on field observations in this week, winter wheat ranged from milk to ready to harvest and spring wheat from heading to soft dough stage depending upon locations. We have pretty much finished stripe rust note-taking in winter wheat nurseries across the state. In western Washington, stripe rust developed to 100% severity on susceptible varieties in our spring wheat experimental field near Mount Vernon (Skagit County). In eastern Washington, stripe rust varied in levels. At Lind (Adams County), susceptible entries of spring wheat had up to 5% severity, similar to the level of last report on June 11. At Walla Walla, spring wheat susceptible varieties had up to 80% severity near Walla Walla (Walla Walla County). Around Pullman (Whitman County), susceptible varieties of winter wheat had 80-100% severity and susceptible spring wheat varieties had up to 50% in our experimental nurseries. In the Syngenta breeding nurseries about five miles southwest of Colfax (Whitman County), up to 100% incidence and 80% severity occurred in some susceptible winter plots, and in the spring wheat field susceptible varieties had up to 100% incidence and 60% severity.

No significant stripe rust was observed in commercial fields of winter wheat and spring wheat due to resistance, early application of fungicides, and the drought since the second week of June in the spring wheat production regions.

Based on the weather forecast, the hot (upper 90s and three-digit temperatures of day time high) and dry weather conditions over this weekend and the next two weeks should stop stripe rust development.

Stripe rust in the country

Severe stripe rust continues damaging crops in Colorado, Nebraska, South Dakota, North Dakota, and Wisconsin, making 2015 another big epidemic year.

Stripe Rust Update, June 11 2015

By 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.

Washington State University