On an annual basis Dr. Xianming Chen, Research Plant
Pathologist, USDA-ARS, Washington State University, issues stripe rust risk
forecasts for the upcoming season (https://www.wawg.org/stripe-rust-report-03-01-stripe-rust-forecast-predicts-moderate-epidemic-level/).
Initially these are based on weather data from November and December of each
year. Based on November 2021 to February 2022 weather data, for the 2022
growing season susceptible varieties are continued to be forecast as having a
moderate risk of stripe rust. Potential yield losses for these
susceptible varieties can range from 20-40%.
Dr. Chen indicates that no stripe rust has been found based on surveys
on November 23, 2021 and most recently on March 1, 2022. As a consequence there may be delayed Pacific
Northwest stripe rust development and traditional herbicide timing fungicide applications
may not be needed. However, should
stripe rust risk and levels increase as the crop progresses into tillering and
stem elongation, later applications towards flag leaf emergence and beyond may
be required. Further updates from Dr. Chen will be shared as they become
available.
In relation to the USA as a whole, Dr. Chen indicates that
no stripe rust has been found except for recent reports from Louisiana and
Texas. The Texas observation is based on
recent reports by Drs. Bryan Simoneaux and Amir Ibrahim from Texas A&M University. They reported stripe rust is developing to
moderate levels at some nursery sites, while trace to sporadic low levels of
leaf rust are occurring in some of their evaluation nurseries. These are “naturally inoculated” nurseries
with wheat currently being at Feekes growth stage 3-5. The PCDMN will continue to monitor reports of
rust development in the USA as the Texas to Nebraska corridor and the Pacific
Northwest regions serve as important sources of leaf stripe and stem rust, and
stripe rust respectively.
Forecasts from Dr. Chen can then be followed up with the
Prairie Crop Disease Monitoring Network (PCDMN) weekly cereal rust risk forecasts
that are issued from mid-May to early July of each growing season. These
forecasts are based on: 1) the occurrence and severity of rust (leaf, stripe
and stem rust) epidemics for source locations in the USA; 2) the occurrence and
frequency of wind trajectories that can carry asexual rust spores from source
USA locations into at risk Prairie regions; 3) Prairie weather conditions that
favour deposition of rust spores and subsequent cereal plant infection and
disease development; and 4) the growth stage of cereal crops.
Background information on the PCDMN cereal rust risk
forecasts can be found at:
https://drive.google.com/file/d/18qX7IbXL40nYpKjLKhJVdwHa0m8Y7-RY/view?usp=sharing.
Weekly PCDMN rust risk forecasts can be found at:
https://prairiecropdisease.blogspot.com/p/cereal-rust-risk-report.html.
If you are planning for the 2022 Prairie growing season and
are concerned about cereal rust risk, a foundational strategy to consider is
growing a variety with the best level of rust resistance available in the
cereal variety you want to grow. Unfortunately, if the variety you are
interested in is rust susceptible then you may need to consider in-crop
fungicide application depending on risk. The PCDMN rust risk forecasts
can help to identify Prairie regions where the rust risk is moderate to high,
and where further in-crop scouting is required to determine whether a fungicide
may be needed.
Weekly Prairie cereal rust risk reports for 2022 will begin
in approximately mid-May and will continue until late June/early July depending
on the US rust situation and crop development.
These can be found at https://prairiecropdisease.blogspot.com/p/cereal-rust-risk-report.html.
All the best for the 2022 Prairie growing season!