Stripe rust update 04/26: Weather favoring stripe rust development

By Xianming Chen
USDA Research Plant Pathologist

On April 24, when we were planting spring wheat nurseries at the Palouse Conservation Farm Station near Pullman in Whitman County, I was checking our winter wheat nurseries. Plants had reached middle jointing stage (Feekes 6), and stripe rust was more widespread than the last report, with almost all susceptible check rows having rust pustules, mostly still on lower leaves. 

On April 25, I was checking commercial wheat fields in Whitman, Adams, and Franklin counties. Winter wheat crops ranged from Feekes 5 to 10. Stripe rust was found in three fields in Franklin County. Although overall incidence of each field was below 1%, one field had a large hot spot of infection about 30 feet in diameter. This field had been sprayed with fungicides. The hot spot indicated that plants were infected before the winter and developed to upper leaves before the winter. Except the hot spot, most infections in these fields were on the middle leaves, indicating the secondary spring infections. The crops in these fields were more advanced (Feekes 8 to 9) than most of the other fields.

As cool temperatures and showers are forecasted for the next few weeks, stripe rust will likely become more widespread. The current recommendations are the same as those made in the previous stripe rust updates, issued on March 1 and April 13. Fungicide application is recommended for the fields planted with moderate to susceptible winter wheat varieties with stripe rust ratings 5 to 9 in the early growth season at the time of herbicide application, and a second application may be needed 20 to 30 days after the first application, which can be determined by whether active stripe rust appears in the field after the first application. 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. 

Stripe rust in the country 

Since the last update on April 13, stripe rust has been reported in several states. So far, stripe rust has been reported in Louisiana, Texas, Washington, Arizona, Oregon, Georgia, Mississippi, Alabama, North Carolina, Oklahoma, and Kansas. 

Stripe rust samples 

We are welcome you to send stripe rust samples to us for race identification. Please use the following shipping address for sending samples: 

Xianming Chen
410 SE Dairy Rd, 114B – 101
Pullman, WA 99164
(509) 335-8086