Around May 16, 2023 we will be issuing our first full cereal
rust risk update. However, for this week
we will provide an indication of rust development in the USA and whether this
poses a risk for the Prairie region.
1)
Rust development in the Pacific Northwest
a)
Dr. X Chen from USDA ARS/Washington State
University, issued their first rust update for 2023 on May 1, 2023. https://www.wawg.org/stripe-rust-report-may-1-no-rust-found-in-commercial-fields/.
b)
Although Dr. Chen reported increased stripe rust
on susceptible wheat and barley in their winter nurseries at Mount Vernon in
the Northwestern Corner of WA; however, no stripe rust was observed in winter
wheat fields several counties in WA and Oregon.
i)
In
southwest BC, Dr. G. Singh, University of British Columbia (UBC) Vancouver
noted natural stripe rust development in a UBC winter wheat disease nursery (https://twitter.com/gurcharn_brar/status/1652865201165815809).
c) As of May 12, 2023, there is a
currently a low risk associated with the PNW being a significant source of
stripe rust inoculum for dispersal into the Prairie region of Canada.
For the PNW, Dr. Chen indicates that given no to low levels of stripe
rust, early season fungicide application is not recommended for winter
wheat. However, he indicates that if
stripe rust is observed then fungicide application should be considered.
2)
Rust Development in the Texas to Oklahoma
corridor
a)
Dr. O. Fajolu with the Cereal Disease Laboratory,
USDA St. Paul, MN issued the first cereal rust bulletin for 2023 on April 27,
2023. Reports were based on updates from
Dr. A. Ibrahim, Texas A&M University, College station, TX, ([CEREAL-RUST-SURVEY]
Rust Evaluation Nursery, Castroville, TX – 15 March 2023). See: https://www.ars.usda.gov/ARSUserFiles/50620500/CRBs/2023%20CRB%20April%2027.pdf.
b)
Stem, leaf and stripe rust of winter wheat and stem
and crown rust of oat have been reported in Texas, while stripe rust was also
reported in Oklahoma.
c)
Increased levels of stem rust were reported in a
stem rust nursery at Castroville, TX that were naturally inoculated. Although low levels of leaf rust were observed
in the same nursery in early March, by mid April high levels were observed. In addition, increased levels of leaf rust were
observed in sentinel trials and/or nurseries in several counties in TX.
d)
Although stripe rust was observed in early March
in a Castroville nursery, later observations in mid March indicated limited
further development, while stripe rust was not active based on observations in
mid April.
e)
Oat stem rust at a Castroville nursery was
limited in late March, but had increased significantly by mid April. Oat crown rust has also been observed at
increased levels in nurseries at Castroville and Weslaco, while it was also
observed at College Station, but at lower levels.
f)
There have been early May reports of trace
levels of leaf and stripe rust on winter wheat at Stillwater, OK, while there
were earlier reports of stripe rust at Chickasha, OK in late April.
(1)
Dr. M. Aoun, Oklahoma State University, Stillwater,
OK, Wheat Disease Update – 10 May 2023, https://spotlight.okstate.edu/wheat-pathology/2023/05/11/wheat-disease-update-10-may-2023/.
(2)
OSU Wheat Pathology, https://twitter.com/OSUwheatdisease/status/1649611333124456449,
https://twitter.com/OSUwheatdisease/status/1653531437503754240,
https://twitter.com/OSUwheatdisease/status/1656454090870915072,
https://twitter.com/OSUwheatdisease/status/1656451012838969344.
g)
As of May 12, 2023, there is a low risk
associated with the Texas/Oklahoma region being a significant source of stem, stripe,
leaf and crown rust inoculum for dispersal into the Prairie region of Canada. This is mainly related to limited rust development
in commercial fields, although rust has been observed in several disease
nurseries.
3)
Rust Development in the Kansas to
Nebraska corridor
a)
Stripe rust was reported at low levels in
Edwards County in Kansas, while the risk of stripe and leaf rust is considered
low as of May 9, 2023 (KSU Wheat Pathology, https://twitter.com/search?q=leaf%20rust&src=typed_query&f=live).
b)
Leaf and stripe rust has also been observed in
inoculated nurseries by Dr. M. Guttieri, USDA ARS/Kansas State University,
Manhattan, KS, April 21 and May 6, 2023 (https://twitter.com/Wheat_MaryG/status/1649414564595789832,
https://twitter.com/Wheat_MaryG/status/1654859732715294721).
c)
As of May 12, 2023, there is a low- risk
associated with the Kansas/Nebraska region being a significant source of stem, stripe,
leaf and crown rust inoculum for dispersal into the Prairie region of Canada. This is mainly related to limited rust development
in commercial fields, although leaf and stripe rust have been observed in
several disease nurseries.
Stay tuned for further Prairie
rust risk updates over the coming weeks!