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Stripe Rust Update, April 22, 2020

Posted by Blythe Howell | May 7, 2020

By Dr. Xianming Chen

Stripe Rust in Eastern Pacific Northwest

Yesterday, I was checking wheat fields in Whitman, Adams, Lincoln, Grant, and Douglas counties in Washington. Winter wheat ranged from Feekes 4 to 7. Minor frost damage on leaf tips was common in Whitman County, caused by freezing night temperatures of the last week. Stripe rust was found only in one commercial field in Lincoln County (Figure 1). The rust incidence was below 1%, and rust was still in low leaves. Three weeks ago, I was checking wheat fields in Whitman, Garfield, Columbia, Walla Walla, Benton, Franklin, and Adams counties in Washington State and Umatilla County of Oregon State on April 1. No stripe rust was found in any checked commercial fields, but rust developed to upper leaves (Figure 2).

The use of fungicides at the time of herbicide application in the early planted winter wheat areas and the dry conditions has kept the rust pressure at a relatively low level so far. However, the rust season still has about three months to go. Any good moisture may increase stripe rust pressure. The use of fungicides at the time of herbicide application for fields grown with moderate susceptible or susceptible varieties (ratings 5-9 in the Seed Buying Guide) is still recommended for both winter wheat (if not applied) and spring wheat. For fields that have already been sprayed with fungicides, check fields for any new infections about 30 days after the fungicide application, and apply fungicides when rust incidence reaches about 5%.

Stripe rust in the country

So far, wheat stripe rust has been reported in Oregon, Washington, Texas, Louisiana, Oklahoma and California. According to Bob Hunger, stripe rust is widespread in Oklahoma. Stripe rust is also severe on some triticale varieties in the Central Valley of California (Figure 3).

Figure 1. Stripe rust observed in a commercial winter wheat field in Lincoln County, Washington on April 22, 2020.

Figure 2. Stripe rust developed to upper leaves in a disease monitoring nursery near Walla Walla, WA on April 1, 2020.

Figure 3. Stripe rust on a triticale variety ‘Trical 158EP’ in Visalia, California (photo courtesy of Gene Aksland, April 20, 2020)

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