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Stripe Rust Light So Far

PULLMAN, Wash. — Thanks in part to recent hot, dry weather, stripe rust has not been much in evidence in the Palouse, according to Xianming Chen, a U.S. Department of Agriculture plant pathologist at Washington State University, who tracks outbreaks of the disease.

That’s good news for the region’s wheat growers, who have witnessed severe outbreaks of the disease the last four years.

Wheat stripe rust shows up as orange pimple-like pustules arranged in fine lines or stripes along wheat leaf veins. A heavy infection on a leaf will impede photosynthesis and affect grain fill. Yields can be reduced by 30 percent to 60 percent in heavily infected fields. Stripe rust also reduces grain quality by lowering test weight.

Checking fields this week, Chen found no stripe rust in the Pullman-Moscow, Idaho, area, and except for the Horse Heaven Hills, no stripe rust was found in commercial fields from Pullman to Walla Walla, and the Connell areas, Chen said.

At the USDA Central Ferry Research Station near Pomeroy, stripe rust was found as hot spots in irrigated experimental plots.

“Stripe rust was spreading on our non-irrigated trap plots near Walla Walla,” Chen said. “Susceptible varieties had up to 60 percent rust severity.”

No rust was found in trap plots and experimental nurseries at Pendleton, Ore., although he found stripe rust as hot spots in experimental nurseries at Hermiston, Ore. Commercial fields near Hermiston and Pendleton were free of the disease.

Farmers shouldn’t get complacent. “Cooler and moist weather forecast in the next week might favor rust development,” Chen said.

If temperatures cool and rains come, Chen urges dryland growers to check their fields the following week. Susceptible varieties in irrigated fields should be monitored more often.

Nationwide, the stripe rust situation mirrors the situation in the Pacific Northwest, Chen said. “Except for severe stripe rust in commercial fields in California, the disease is generally light throughout the country due to dry conditions.”

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