Warm, dry weather stopping rust

From Xianming Chen

Rusts in the Palouse Region

We were checking fields of wheat and barley in the Palouse region (including Whitman County of Washington and Latah County of Idaho) on July 7, 2017. Winter wheat crop ranged from soft dough to almost mature; spring wheat crop from boot to milk; and spring barley from headed to milk. The rust situations are the following:

Wheat stripe rust. Active stripe rust pustules were still found on green leaves of some winter wheat fields in both commercial and experimental fields. For spring wheat, stripe rust reached 100 percent on susceptible varieties in experimental fields around Pullman. In commercial fields, stripe rust was low, less than 1 percent incidence and up to 10 percent severity in most fields checked. The low level of stripe rust in commercial fields is due to cultivar resistance and/or application of fungicides in the early season. With the dry and hot weather conditions in the last couple of weeks and similar weather conditions forecasted for the next two to three weeks, HTAP resistance in many spring wheat cultivars has become effective, and stripe rust development will be slowed down or stopped. Except in fields of very late crops that still have good soil moisture, fungicide application is no longer needed.

Barley stripe rust. Low to moderate levels of barley stripe rust were observed in experimental fields. In commercial fields, stripe rust was found at very low levels in only one barley field in Latah County.

Wheat leaf rust. In monitoring and variety trial nurseries, leaf rust was found in several plots of winter wheat. In commercial fields, leaf rust was also found in several winter wheat fields near Farmington in Washington and Potlatch in Idaho. Incidence was less than 1 percent and severity less than 10 percent. No leaf rust was found in any spring wheat fields.

Stem rust. No stem rust was found in any of winter and spring wheat fields, and nor in barley fields.

Rusts in Western Washington

In our experimental nurseries at Mount Vernon in western Washington, wheat stripe rust reached 100 percent severity on susceptible spring wheat by the end of last week. Barley stripe rust was up to 60 percent severity. Wheat leaf rust was low. In contrast to the situations of severe barley leaf rust in the recent years, barley leaf rust was much lower this year, which could be due to the relatively late planting.

Wheat Stripe Rust in the U.S. and Canada

Wheat stripe rust has been reported in Texas, Louisiana, Arkansas, Mississippi, North Carolina, Oklahoma, Kansas, Washington, Oregon, Wisconsin, Virginia, Delaware, Tennessee, Michigan, Kentucky, Nebraska, Indiana, Georgia, Idaho, Arizona, California, Montana, Colorado, South Dakota, Minnesota, North Dakota and New York. Wheat stripe rust has been reported in Alberta, Ontario, Manitoba and Saskatchewan provinces of Canada.

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