Stripe Rust Alert 4/17/07

April 17, 2007

Xianming Chen
Wheat stripe rust is developing in Horse Heaven Hills

Today, I was checking wheat fields in the Horse Heaven Hills. Winter wheat crop ranges from stage 4 to 6. Stripe rust was found almost in every checked field. Rust severity ranges from 2 to 10%. With good moisture in soil and favorable weather conditions, stripe rust should develop rapidly from now on in the hard red winter wheat area. Growers in this region should check your fields more closely because major hard red wheat cultivars are moderately susceptible to highly susceptible. Please consider using fungicides when rust severity reaches 10 to 15%. This range is higher than our normal threshold because the crops have not reached to the flag-leaf stage and a little bit delayed spray could protect more of the late stages. However, growers in this region should not wait too long because the good rain a couple days ago and continued moisture conditions provide ideal conditions for rust infection. As the weather is getting warmer, rust will show up quickly.

No rust was found in the Walla Walla area today. However, as stripe rust is significant and continues developing in the Horse Heaven Hills region, growers in the Walla Walla area should start to check their fields, especially for fields grown with cultivars that were susceptible in the past. Growers in other regions should start checking winter wheat fields in two to three weeks. If the weather conditions continue to be favorable to stripe rust, the Pacific Northwest may have an epidemic. Spring wheat crops may be more vulnerable because many cultivars are susceptible to stripe rust.

As usual, stripe rust developed to 50% severity on susceptible cultivars in our experimental plots at Mt. Vernon, Washington by the first week of April.

Stripe rust situation in other states.

Stripe rust is light in California due to drought conditions and has been reported in Louisiana, Arkansas, and Texas, but generally light due to the combination of dry weather and recent frozen temperatures.

If you have questions, please contact Xianming Chen (509-335-8086, xianming@wsu.edu), Kelley Richardson (509-335-4789, klrichardson@wsu.edu), or David Wood (509-335-4789, dawood@mail.wsu.edu)