This is an update to a PCDMN post on January 9, 2024. Updated information from the Pacific Northwest (PNW) of the US provides a further head’s up regarding potential Prairie stripe rust risk in 2024. In his March 1, 2024 update, Dr. X. Chen, with USDA-ARS and Washington State University, indicates the risk of stripe rust for 2024 for the eastern PNW is severe and susceptible winter wheat varieties will potentially incur yield losses in the 40-60% range if they are not sprayed with fungicide. The projected yield loss for highly susceptible varieties has increased from 42% with the January 2024 update (https://www.wawg.org/stripe-rust-report-warmer-november-december-dont-bode-well-for-susceptible-varieties/https://smallgrains.wsu.edu/first-stripe-rust-forecast-of-the-2024-season/) to 51% for the March 1, 2024 update (https://www.wawg.org/march-1-stripe-rust-forecast-calling-for-epidemic-levels-for-eastern-washington/). Fortunately, varieties with moderate to high levels of resistance will mitigate stripe rust risk and the need for fungicide. However, virulence shifts can occur so keep this in mind if you start to see more stripe rust than expected in any resistant varieties you are growing on the Prairies. Dr. Chen also indicated in his March 1, 2024 update that stripe rust appears to have successfully survived the winter on infected winter wheat crops, with multiple reports of symptoms in recently checked rust monitoring nurseries and commercial fields. Moreover, these 2024 observations in Washington State, especially east of the Cascade mountains, are earlier compared to 2011 to 2023. Overall, the PNW may have levels of stripe rust in 2024 that could threaten Prairie winter and spring wheat crops.
Unfortunately, Dr. Chen also indicated in his March 1, 2024 update that there have been multiple reports of stripe rust in Texas and other southcentral States and these early observations suggest that these areas of the US may experience severe stripe rust epidemics if conducive weather occurs. Observations of stripe rust in Texas by Texas A&M staff were recently posted by S. Baker, Texas A&M AgriLife Research, based on observations by J. Baker and D. Hathcoat (S. Baker, Stripe rust at Chillicothe, TX, CEREAL-RUST-SURVEY@LISTS.UMN.EDU, February 26, 2024; https://twitter.com/J_SBaker/status/1752818506674929882)
Each year the PCDMN issues weekly cereal rust risk forecasts based on rust development in source locations in the USA. The PNW is mainly a concern in terms of stripe rust, while the Texas to Nebraska corridor represents a risk for leaf rust, stripe rust and stem rust, while there may be concerns related to crown rust in oat. In addition to accounting for rust development in the US, the PCDMN also looks at the number of wind trajectories that may carry rust spores from US source locations, and Prairie crop development and weather conditions.
You can keep up-to-date with Prairie cereal rust risk via PCDMN cereal rust risk forecasts that are posted to this blog from mid-May to early July each year and 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. It is advised that Prairie producers check the stripe rust resistance rating of the winter and spring wheat varieties they are or will be growing. Timely scouting and consideration of fungicide use are advised for the 2024 growing season, especially for varieties that are susceptible to moderately susceptible to stripe rust.
The PCDMN will follow up with further risk reports from Dr. Chen as we move towards the 2024 Prairie growing season.
Typical symptoms of stripe rust are as follows:
