By Dr. Xianming Chen
On Wednesday, we were checking wheat fields in Whitman, Lincoln, Douglas, Grant, Adams, Franklin, Benton and Walla Walla counties of Washington. Winter wheat crops ranged from Feekes 3 to 6. No rust was found in any commercial fields in these counties. Even in the field of Grant County in which stripe rust was found quite easily last November, stripe rust was not found, indicating that the cold winter has killed rust. However, we found stripe rust on susceptible varieties in our experimental field in Walla Walla. In this less-than-a-half-acre field, we were able to found five separate infection sites, each with 2-4 low leaves having active stripe rust pustules, indicating that the plants were infected last fall, and stripe rust fungus has survived the winter in this area. Compared to the last year, the appearance of stripe rust in Walla Walla is much later and in a much lower level.
The current stripe rust pressure is low. Use or not use fungicides at the time of herbicide application depends on regions. For the Walla Walla region and further south into northeastern Oregon, fungicides may be needed for fields planted with susceptible or moderately susceptible varieties (stripe rust ratings 5-9 in the Seed Buyer’s Guide), while resistant and moderately resistant varieties with ratings 1-4 may not need fungicides. For areas further north, stripe rust may not appear until in two to three weeks, and fungicide application may not be needed for any varieties in the early season. As the crop season is late and soil moisture is good this year, stripe rust may develop to damaging levels in late season, and fungicide application in flag-leaf to grain filling stages may be needed for moderate susceptible and susceptible varieties. It is always a good idea to check fields and apply fungicide when stripe rust is found.
Stripe Rust in Other States
So far, wheat stripe rust has been reported in Texas, Louisiana, Mississippi, Oklahoma, Kansas and Washington; barley stripe rust has been reported in western Oregon. Although the current distribution is not as wide as this time of the last year, wheat stripe rust may still be able to cause localized damage. Check fields and use fungicides when needed.