Stripe rust (copy)

Stripe rust on wheat.

Stripe rust will intensify in Washington wheat fields as the weather warms up, a USDA expert says.

"Even though it started quite late this year, due to very cold and wet weather conditions, rust has developed quite fast in recent weeks and (is) also expected to develop faster," Xianming Chen, research plant pathologist, told the Capital Press.

The fungus causes yield reductions.

Stripe rust has become "relatively easy to spot," Chen said.

He's received reports of rust in fields planted with the varieties UI Magic and Curiosity in Adams, Benton, Franklin, and Walla Walla counties, and a field planted with Stingray in Whitman County.

Last year there was almost no rust. This year will be a "normal epidemic year," Chen said. Susceptible wheat varieties could experience a 38% yield loss. Commercially grown varieties could see a loss of up to 30% without treatment.

Some areas are already past the fungicide application window for winter wheat, but Chen still recommends they check their fields, particularly if susceptible varieties were planted.

For fields sprayed with fungicides more than 20 days ago, a second application may be considered if active rust pustules can be spotted, Chen said in his June 17 update to growers.

Because high-temperature adult-plant resistance to stripe rust does not work maximally under the cool and wet conditions in recent weeks, it is critical to check fields planted with varieties with stripe rust ratings 4-5 over the next two weeks, he said in his update.

Spring wheat farmers who have not yet sprayed with a herbicide should also apply a fungicide, Chen said.

Due to the drought last year, Chen was only able to collect data in the Mount Vernon area, west of the Cascades.

Rust has more variation each year in the eastern side of the state than the western side, he said.

This year, he had to inoculate experimental fields near Pullman in late April due to the fungus' slow development.

"Favorable conditions made the rust develop in recent weeks very fast," Chen said.

Rust was "very severe" in the Walla Walla area the week of June 13, he said.

"When we walk out of the fields, the pants get orange-colored," he said.

So far, wheat stripe rust has been reported in Oregon, Washington, California, Louisiana, Texas, Georgia, Oklahoma, and Maryland and on triticale in California, according to Chen's report. Barley stripe rust has been reported in Washington and California.

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Field Reporter, Spokane

I have been covering wheat and other topics for Capital Press since 2008. Recent stories include radicchio, emus, aphids and a Q&A with Washington Gov. Jay Inslee. If you have a news tip, please contact me at 509-688-9923 or mweaver@capitalpress.com

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