Wind trajectory and cereal rust risk assessment and need for in-crop scouting in the Prairie region, June 23-29, 2020
1. Pacific Northwest
i. There were a moderate number of reverse wind trajectories that passed over the PNW region and into the prairies. Locations with the highest number of days with events (4-5) with reverse trajectories from the PNW included: Lethbridge (5), AB; and Gainsborough (5), Kindersley (4), and Regina (5) SK. The remaining locations in Alberta, Saskatchewan and Manitoba had 1-2 days with events, except for Fort Vermilion, Grande Prairie, Manning, Sedgewick and Wanham, AB, which had no events from June 23-29, 2020 (Table 1).
ii. Currently there appears to be relatively low levels of stripe rust development on commercial winter wheat crop in the PNW. The spring wheat crop is somewhat smaller in acreage and appears to have limited stripe rust development, while fungicide applications may limit further stripe rust development in PNW spring wheat crops.
iii. Prairie temperatures were warmest in MB and eastern SK and seven day cumulative varied across the prairies (Figure 7). Average 7 day temperatures continue to be warmest across MB and eastern SK and coolest across most of AB (Figure 7) . The weekly average temperature at Winnipeg (20.8 °C) was 6 °C warmer than Grande Prairie. Cumulative rainfall for the past 7 days was variable (Figure 9). Cumulative 30 day rainfall was greatest across central regions of AB. Rainfall amounts were lower across the southern prairies (Figure 10).
iv. Winter wheat crops are progressing into flowering or are finishing flowering, while Prairie spring wheat development ranges from tillering to booting/head emergence.
v. There have been reports of stripe rust in western Idaho and on June 16 and June 30, 2020 from southern Alberta, specifically the Counties of Lethbridge, Cardston, and Forty-Mile. On June 19, 2020 there was a report in Alberta with the observation of stripe rust in winter wheat yield trials at AAFC Beaverlodge. Stripe was also just observed in wheat plots at the University of Saskatchewan in Saskatoon (Randy Kutcher, personal communication). Given the appearance of stripe rust in three counties in southern Alberta, at Beaverlodge in the Country of Grande Prairie, and the first observations in the Saskatoon area of Saskatchewan, farmers in these regions should be on the look out for stripe rust in wheat. Special focus should be on wheat fields seeded to varieties rated as susceptible or moderately susceptible. These recent observations indicate that Prairie regional sources of inoculum may become more important with further crop and disease development.
vi. Thus, as of June 29, 2020 the risk of stripe rust appearance from the PNW or from regional sources is low to moderate (Figure 12). However, some locations may be at an increased stripe rust risk, especially where there were 4-5 reverse trajectory events from the PNW or in Prairie regions where stripe rust has been reported.
2. Texas-Oklahoma corridor
i. Currently, farmers in Texas and Oklahoma have or will soon be finished harvesting their winter wheat crops, and thus no longer represents a significant source of cereal rust inoculum for movement into the Prairie region.
ii. Thus, as of June 29, 2020 the risk of leaf and stripe rust appearance from the Texas-Oklahoma corridor is nil and scouting for these diseases is not urgent.
ii. Thus, as of June 29, 2020 the risk of leaf and stripe rust appearance from the Texas-Oklahoma corridor is nil and scouting for these diseases is not urgent.
3. Kansas to Nebraska corridor
i. Currently there appears to be relatively low levels of stripe rust development in the Kansas to Nebraska. Looking at specific locations in Prairie region and reverse trajectories, only 8 of 29 locations had only 1-2 days each with reverse trajectories originating over the states of Kansas and Nebraska from June 23-29, 2020, with the remaining locations having zero. Locations with 1-2 days with events included: Gainsborough (2), and Yorkton (1), SK; and one event each for Brandon, Carman, Dauphin, Portage, Russell, and Selkirk, MB. The remaining locations had no events from June 23-29, 2020 (data not shown).
ii. Prairie temperatures were warmest in MB and eastern SK and seven day cumulative varied across the prairies (Figure 7). Average 7 day temperatures continue to be warmest across MB and eastern SK and coolest across most of AB (Figure 7) . The weekly average temperature at Winnipeg (20.8C) was 6C warmer than Grande Prairie. Cumulative rainfall for the past 7 days was variable (Figure 9). Cumulative 30 day rainfall was greatest across central regions of AB. Rainfall amounts were lower across the southern prairies (Figure 10).
iii. Winter wheat crops are progressing into flowering or are finishing flowering, while Prairie spring wheat development ranges from tillering to booting/head emergence.
iv. In Kansas the winter wheat crop is rapidly maturing with harvesting occurring in some areas, and thus no longer represents a significant source of rust inoculum. The Nebraska winter wheat crop has mostly headed and in some areas is starting to turn with harvest 1-2 weeks away. With the Nebraska winter wheat crop progressing towards maturity and harvest, and given limited reports of disease, this state is becoming less of a potential source of rust inoculum.
v. Thus, as of June 29, 2020 the risk of leaf and stripe rust appearance from the Kansas-Nebraska corridor is limited and scouting for these diseases is not urgent (Figure 13).
vi. There continue to be reports of low levels of stripe rust in South Dakota and Wisconsin. Thus, given the proximity to the Prairie region, these reports serve as a warning that farmers and crop scouts in the central to eastern Prairie region of Canada should be on the look out for stripe rust, especially in winter wheat fields.
ii. Prairie temperatures were warmest in MB and eastern SK and seven day cumulative varied across the prairies (Figure 7). Average 7 day temperatures continue to be warmest across MB and eastern SK and coolest across most of AB (Figure 7) . The weekly average temperature at Winnipeg (20.8C) was 6C warmer than Grande Prairie. Cumulative rainfall for the past 7 days was variable (Figure 9). Cumulative 30 day rainfall was greatest across central regions of AB. Rainfall amounts were lower across the southern prairies (Figure 10).
iii. Winter wheat crops are progressing into flowering or are finishing flowering, while Prairie spring wheat development ranges from tillering to booting/head emergence.
iv. In Kansas the winter wheat crop is rapidly maturing with harvesting occurring in some areas, and thus no longer represents a significant source of rust inoculum. The Nebraska winter wheat crop has mostly headed and in some areas is starting to turn with harvest 1-2 weeks away. With the Nebraska winter wheat crop progressing towards maturity and harvest, and given limited reports of disease, this state is becoming less of a potential source of rust inoculum.
v. Thus, as of June 29, 2020 the risk of leaf and stripe rust appearance from the Kansas-Nebraska corridor is limited and scouting for these diseases is not urgent (Figure 13).
vi. There continue to be reports of low levels of stripe rust in South Dakota and Wisconsin. Thus, given the proximity to the Prairie region, these reports serve as a warning that farmers and crop scouts in the central to eastern Prairie region of Canada should be on the look out for stripe rust, especially in winter wheat fields.
4. Rust appearance in the Prairie region
i. Where farmers or consultants noticed stripe rust development on winter wheat in the fall of 2019, it is recommended to scout winter wheat fields that have resumed growth in spring 2020. Scouting is especially critical where the variety being grown is susceptible to stripe rust.
ii. Currently, there have been five reports of the initial appearance of stripe rust on Alberta winter wheat on June 5, 16, 19, and 30, 2020 in the Counties of Lethbridge, Cardston, and Forty-Mile in southern Alberta and in the County of Grande Prairie in the Peace Region of Alberta (Figure 2). On July 2, 2020 there was also an initial report of stripe rust in the Saskatoon region (R. Kutcher, personal communication). Given the appearance of stripe rust, farmers in these regions should be on the look out for stripe rust in wheat. Special focus should be on wheat fields seeded to varieties rated as susceptible or moderately susceptible.
i. Where farmers or consultants noticed stripe rust development on winter wheat in the fall of 2019, it is recommended to scout winter wheat fields that have resumed growth in spring 2020. Scouting is especially critical where the variety being grown is susceptible to stripe rust.
ii. Currently, there have been five reports of the initial appearance of stripe rust on Alberta winter wheat on June 5, 16, 19, and 30, 2020 in the Counties of Lethbridge, Cardston, and Forty-Mile in southern Alberta and in the County of Grande Prairie in the Peace Region of Alberta (Figure 2). On July 2, 2020 there was also an initial report of stripe rust in the Saskatoon region (R. Kutcher, personal communication). Given the appearance of stripe rust, farmers in these regions should be on the look out for stripe rust in wheat. Special focus should be on wheat fields seeded to varieties rated as susceptible or moderately susceptible.
