Rust outbreak could offset ‘million dollar’June rainfall

June precipitation is generally greeted as “Million Dollar Rains” in Whitman County. This year, however, heavy rain in this key month may prove to be something else.

Rain in the next couple weeks will block fungicide application, needed now because of a potential serious outbreak in stripe rust infection in Palouse wheat.

Stripe rust is a fungus that attacks chaff, leaves and leaf sheath of wheat. Infection kills the leaves of a plant, thus reducing its ability to produce nutrients needed for kernel development. That hits hard by lowering the weight of kernels at harvest time.

Xianming Chen, plant pathologist for the USDA Agricultural Research Service in Pullman, said heavy May and June rains have created ideal conditions for stripe rust.

In a stripe rust alert issued last week, Chen said surveys of fields across eastern Washington found widespread rust in wheat fields.

The rust fungus appears each year, but can develop into epidemic proportions under the right circumstances.

Hot spots were found in winter wheat fields west of Colfax and one north of St. John, with rust infecting 100 percent of their crops, some up to 80 percent severity.

Rust pustules on necrotic strips found on crops in those fields showed potential evidence the rust varieties could be overcoming resistance traits built into the plants and even fungicide, he said.

Built-in resistance to stripe rust kicks in based on atmospheric temperatures.

High-temperature adult plant resistance should kick in with this week’s warmer temperatures in the Tubbs 06, Simon, Xerpha, Rod/Tubbs 06, Lambert, Masami, WB-528, AP700CL, RJames, ORCL 103, Farnum and Bauermeister varieties.

While most winter wheat fields have been already sprayed, Chen said spring wheat fields may be susceptible to rust infection. He cautioned, though, that growers of spring wheat in the northern and eastern portions of the county should wait until this weekend to gauge their crops for spraying.

He recommended using the Folicur, Tilt, Quilt, Quadris, Stratego and Headline chemicals to combat rust.

Most fungicides, though, can only be used before wheat flowers, which is coming nearer.

Chen recommended spraying varieties AP Legacy, Salute, KCF9003, CDC Ptarmigan, Paladin, Eddy, Finley, Goetze, Finway and Buchanan.

The varieties Eltan, Madsen, Eltan/Madsen, Chukar, Finch, Skiles, ORCF-102, Coda, Madsen/Rod, Legion, Bitteroot, Breuhl, Stephens, Brundage, Eltan/Tubbs06, KCF9002, Goetze/Skiles, Cara and George should not be sprayed.

Chen said farmers with fields of susceptible varieties should wait until their field has five to 10 percent stripe rust before applying a fungicide.