The full weekly cereal rust risk report for June 7-13, 2023 will be delayed as we are waiting on location specific wind trajectory data for the Pacific Northwest (PNW) and the Kansas/Nebraska (KS/NE) regions.
However, in terms of total trajectory numbers there was a substantial reduction in the number of trajectories from the PNW (40 versus 104 last week), Texas/Oklahoma (TX/OK) (17 versus 98 last week), and KS/NE (46 versus 119). Note most of the KS/NE and TX/OK trajectories would have primarily passed over locations in Saskatchewan and Manitoba, while trajectories from the PNW would have mainly passed over locations in Alberta and western Saskatchewan.
A recent update from Dr. Chen, USDA ARS/WSU, Pullman, WA (Rust update June 13, 2023, https://striperust.wsu.edu/?post_type=post&p=3639) continues to indicate limited development of stripe rust in commercial cereal fields. However, observations of increased levels were noted in a number of screening trials for both winter and spring wheat and barley. Dr. Chen indicates that the "rust season" is over for winter wheat, although recent rains and moderate temperatures may favour development in spring cereal crops.
Previous PCDMN cereal rust risk reports indicated limited rust development in Texas and Oklahoma. These regions are likely no longer a significant source of rust inoculum given that most winter wheat and oat crops are likely mature with 42 and 28% of the winter wheat and 60 and 5% of the oat crops being harvested as of June 11, 2023, for Texas and Oklahoma, respectively (https://quickstats.nass.usda.gov/results/5803D4B1-7DF2-36E9-B294-11222030BF1A; https://quickstats.nass.usda.gov/results/08843EBD-FC53-33BC-BD7F-81F3751B687C).
Over the last week there continue to be reports of stripe rust and stem rust in winter wheat from Kansas. In general, the levels of leaf, stripe and stem rust are low, although on susceptible varieties low-moderate stem rust levels were recently observed in Republic County, North Central Kansas (Dr. K. Onofre, Stem Rust Detection in Kansas, CEREAL-RUST-SURVEY@LISTS.UMN.EDU, June 13, 2023; Dr. E. DeWolf, More stem rust activity in Kansas, CEREAL-RUST-SURVEY@LISTS.UMN.EDU, June 14, 2023).
Recently Dr. E. DeWolf, indicated that moderate amounts of stripe rust have been reported from Northwest Kansas (Dr. E. DeWolf, More stem rust activity in Kansas, CEREAL-RUST-SURVEY@LISTS.UMN.EDU, June 14, 2023; Dr. E. DeWolf, Stripe Rust Update from Kansas, CEREAL-RUST-SURVEY@LISTS.UMN.EDU, June 15, 2023; Figures 1 and 2). In their June 15 update Dr. De Wolf reports that levels of stripe rust were low in mid-May in central Kansas, while in west central and NW areas the disease moved in late as crops were moving into head emergence and anthesis. In these NW and west central areas susceptible varieties are now showing high incidence and moderate severity levels. Overall, Dr. De Wolf reports that stripe rust appearance was delayed in 2023.
As of the period of June 7-13, 2023, the overall Prairie cereal rust risk assessment and need for in-crop scouting is as follows:
Pacific Northwest – There was a lower number of reverse wind trajectories that passed over the PNW region and into the Prairies versus May 31-June 6. Given this, and limited stripe rust development in the PNW and generally dry Prairie conditions especially in western regions, as of June 13, 2023 the risk of stripe rust appearance from the PNW is low and scouting for this disease in the Prairie region is generally not urgent.
Texas-Oklahoma corridor – Given limited leaf, stem, stripe and crown rust development in this corridor, generally dry eastern Prairie conditions and that most crops are approaching maturity or are being harvested, as of June 13, 2023 the risk of stem, leaf, stripe, and crown rust appearance from the Texas-Oklahoma corridor is generally limited and scouting for these diseases in the Prairie region is not urgent.
Kansas-Nebraska corridor – Given a lower number of wind trajectories from this region, generally limited leaf, stem, stripe and crown rust development in this corridor, and generally dry eastern Prairie conditions (Figure 3), as of June 13, 2023 the risk of stem, leaf, stripe, and crown rust appearance from the Kansas-Nebraska corridor is generally low and scouting for these diseases in the Prairies is not urgent. However, recent reports of increasing levels of stripe rust in NW and west central Kansas, and the continued observation of stem rust in Kansas commercial fields may represent an emerging concern. These observations are a concern, especially for the central to eastern Prairie regions with rainfall over the last 2-4 days. Farmers and consultants in the central-eastern Prairies should consider keeping an eye out for stripe and stem rust development, especially in fields planted to susceptible varieties.
