WAWG
By Dr. Xianming Chen
Research Plant Pathologist, USDA-ARS
In the last two weeks, we were planting spring cereal nurseries and checking winter wheat fields in various locations. So far, we have found stripe rust in our disease monitoring and germplasm screening fields in various locations except those around Pullman.
On April 9, our crew found stripe rust in our winter crop nursery at Walla Walla, Wash., and we rechecked the field on April 17. The crop reached Freekes 6-7. Stripe rust was easy to find in the border rows planted with the susceptible check, and the rust incidence reached 5%. Compared to this time last year, stripe rust has not reached the last year’s severity level at this location. We checked some commercial fields in the area, but did not find rust. On April 14, our crew also found stripe rust in our winter crop nursery at Lind, Wash., and the incidence was higher than the same time last year.
On April 15, we were checking the winter wheat field in Lincoln County where we found stripe rust last November, but did not find rust. On April 15 and 16, we were collecting stripe rust data on winter nurseries in Mount Vernon, Wash., stripe rust reached up to 70% severity on susceptible entries, as severe as usual for this location in western Washington. On April 17, we were checking our winter wheat monitoring nursery in Hermiston, Ore., and found stripe rust had just started. On April 17, we found stripe rust in our winter crop nurseries in Central Ferry, Wash. Winter wheat reached Feekes 7-8 and barley to Feekes 10. Stripe rust was easy to find on susceptible checks, and the incidence and severity were higher than those of last year at this location.
On April 17, we were checking our winter wheat nurseries at the Palouse Conservation Field Station near Pullman, Wash., and did not see any rust. Last year, stripe rust was easy to see in the first week of April. For the Palouse region, stripe rust normally starts in the first week of May.
In the eastern Pacific Northwest, stripe rust started relatively late compared to last year, but the disease can develop to an epidemic considering the high moisture so far and favorable forecast weather (both temperature and precipitation) in the next several weeks. Based on the current stripe rust situation and the new prediction, our recommendations are changed from those issued in early March. Fungicide applications are recommended for winter wheat fields planted with susceptible and moderately susceptible varieties (stripe rust ratings 6 to 9) before flowering. For spring wheat, if you have not planted, please choose resistant or moderately resistant varieties (stripe rust ratings 1-4). For fields planted with susceptible (stripe rust rating 8 and 9) or moderately susceptible (stripe rust ratings 6 and 7) varieties, please consider fungicide application at the time of herbicide application. It is always recommended to check your fields. If you see active rust or rust incidence or severity reaches 5%, apply fungicides as soon as possible.
Stripe rust in the country
So far, stripe rust has been reported in Louisiana, Texas, Georgia, Washington, and Oregon. Compared to last year, stripe rust has been relatively low countrywide, but the disease can develop quickly under favorable weather conditions. Growers should check their wheat fields for signs of stripe rust and apply fungicides when needed, following recommendations in your region.