T.K. Turkington, R. Aboukhaddour, and B. McCallum.
Previous PCDMN blog posts have highlighted
potential emerging stripe rust issues in the USA; unfortunately, this may mean
stripe rust issues for Prairie wheat growers. The most recent reports from Dr.
Chen, USDA-ARS and Washington State University (WSU), indicated continued development
of stripe rust in research plots and commercial fields (https://smallgrains.wsu.edu/stripe-rust-24/, https://striperust.wsu.edu/2024/04/28/stripe-rust-update-april-26-2024/).
Incidence levels in commercial fields were
generally low, although Dr. Chen did observe a hot spot of elevated severity in
a commercial field. Dr. Chen cautions
that forecast cool weather and rainfall could promote further development of
stripe rust. As mentioned previously Dr. C. Hagerty of the Columbia Basin
Agricultural Research Centre (CBARC), Oregon State University also reported
stripe rust on susceptible lines at the CBARC, Pendleton, OR and encouraged
growers to scout and consider fungicide application (https://osu-wams-blogs-uploads.s3.amazonaws.com/blogs.dir/2823/files/2024/04/2024_April_Rust.pdf). Recent X (formerly Twitter) posts from Dr. D.
Larkin, wheat Breeder Limagrain, April 18, 2024, (https://twitter.com/dylarkin/status/1781102306593050890)
Reports continue regarding stripe rust in Texas, Oklahoma and Kansas, and these early observations suggest these regions may experience severe stripe rust epidemics if conducive weather occurs over the next several weeks. Maps from Kansas State University and AG PEST Monitor: Wheat, indicate stripe rust development in numerous counties in Oklahoma and Kansas (Figures 1 and 2, https://wheat.agpestmonitor.org/stripe-rust/, https://eupdate.agronomy.ksu.edu/article_new/stripe-rust-distribution-and-risk-assessment-for-kansas-april-25-2024-589-5). As mentioned in the PCDMN blog post from April 19, 2024, Drs. S. Liu, B. Gerrish, and J. Rudd, Texas A&M University reported stripe rust, as well as leaf and stem rust of wheat, and crown and stem rust of oat in Texas (https://varietytesting.tamu.edu/wp-content/uploads/sites/17/2024-Wheat-Rust-Report.pdf). Earlier in April, Dr. M. Aoun, OSU reported that stripe rust potentials were high in Oklahoma and timely scouting by farmers was encouraged (https://spotlight.okstate.edu/wheat-pathology/2024/04/02/wheat-disease-update-2-april-2024/, https://www.farms.com/videos/crops/scout-for-stripe-rust-209386.aspx). Most recently, Dr. M. Aoun reported increased levels of stripe rust on winter wheat at Stillwater and Chickasha, OK, while leaf rust was also noted (https://twitter.com/OSUwheatdisease/status/1784421264242720939). In an article by L. Vihauer, High Plains Journal, Dr. M. Aoun indicates significant development of stripe rust in SE Oklahoma, although conditions are dry and rain is needed, which will increase stripe rust risk (https://hpj.com/2024/04/19/stripe-rust-a-concern-in-oklahoma-wheat/). On April 29, 2024, Dr. B. Carver, Oklahoma State Wheat Improvement Team also mentioned continued development of leaf rust on winter wheat in central regions of Oklahoma (https://twitter.com/osuwit/status/1785003699426689353).
In western Canada, early development of stripe rust in disease nurseries at Abbotsford and Creston, BC have been reported by Dr. G. Brar, U of Alberta, formerly of UBC, and likely reflect overwintering on winter wheat breeding lines (https://x.com/gurcharn_brar/status/1779910374051209644).
Overall, US rust risk forecasts and the early widespread occurrence symptoms suggest the PNW and the Texas to Kansas corridor may be important sources of stripe rust inoculum for Prairie wheat growers in 2024. Currently, Prairie winter wheat crops resuming growth are most at risk. Fortunately, most winter wheat varieties have intermediate to high levels of resistance, although Radiant, CDC Buteo, AAC Elevate, Broadview, and CDC Falcon are rated as susceptible (https://www.seed.ab.ca/variety-data/cereals/; https://saskseed.ca/wp-content/uploads/2020/12/2024-Varieties-of-Grain-Crops.pdf; https://www.seedmb.ca/pdf-editions-and-separate-section-pdfs/).
The Prairie Crop Disease Monitoring Network (PCDMN) will be starting their weekly Prairie rust risk forecasts shortly, and these can be found at https://prairiecropdisease.blogspot.com/p/cereal-rust-risk-report.html. Key management strategies for cereal rusts include host resistance, scouting and awareness of emerging rust issues, and timely fungicide application. Previous PCDMN Twitter (X) and Blog posts provide additional background information on potential yield losses due to stripe rust as well as the importance of monitoring crops for cereal leaf diseases:
https://twitter.com/pcdmn/status/1306577312465522690;
https://twitter.com/pcdmn/status/1280178253295169537;
https://prairiecropdisease.blogspot.com/2022/06/scouting-and-risk-assessment.html;
https://prairiecropdisease.blogspot.com/2023/07/end-of-season-assessment-of-cereal-leaf.html
https://twitter.com/pcdmn/status/1347656233243828224
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| Figure 1. USA stripe rust observations, April 25, 2024, courtesy of AG PEST MONITOR: Wheat, https://wheat.agpestmonitor.org/stripe-rust/. |
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| Figure 2. Stripe rust occurrence, Kansas, April 25, 2024, Agronomy eUpdates. Courtesy of Dr. K. Onofre, Extension Plant Pathologist, Department of Agronomy, Kansas State University, https://eupdate.agronomy.ksu.edu/article_new/stripe-rust-distribution-and-risk-assessment-for-kansas-april-25-2024-589-5. |
