Wind trajectory and cereal rust risk assessment and need for in-crop scouting in the Prairie region, June 9-15, 2020
1. Pacific Northwest – There were a relatively high number of reverse wind trajectories that passed over the PNW region and into the prairies. Locations with the highest number of days with events (3-4) with reverse trajectories from the PNW included: Beiseker (4), Lethbridge (4), and Olds (3), Provost (3), Rycroft (3), Vegreville (4), Wanham (3), AB; Gainsborough (3), Kindersley (3), Saskatoon (3), and Tisdale (3), SK. Of note is the occurrence of 3 days with trajectory events that ended up in the Wanham area in the Peace Region of Alberta (Table 1). Currently there appears to be relatively low levels of stripe rust development in the PNW, although this may change over the few weeks along fungicide applications may limit further stripe rust development in PNW winter wheat crops. Temperatures have been 2-3C above normal in southern Alberta, and most of Saskatchewan and Manitoba. In southcentral Alberta to the Peace River region in Alberta, temperatures have been normal to slightly below normal. Rainfall amounts were greatest in AB and southern/east-central SK, while eastern and southern Alberta, central to western Saskatchewan and most of Manitoba, except the SE corner had minimal amounts of rainfall. Winter wheat crops are progressing towards head emergence with some starting to flower, while there are generally early stages of Prairie spring wheat development ranging from the two leaf to tillering stages. There have been reports of stripe rust in western Idaho and in the last week from southern Alberta, specifically the County of Lethbridge. Thus, given the proximity to the Prairie region, these reports serve as a warning that farmers and crop scouts in the western Prairie region of Canada should be on the look out for stripe rust, especially in winter wheat fields in southern Alberta. These recent observations in southern Alberta indicate that Prairie regional sources of inoculum may become more important with further crop and disease development. Thus, as of June 15, 2020 the risk of stripe rust appearance from the PNW or from regional sources is low to moderate. However, locations with 3-4 reverse trajectory events from the PNW or in Prairie regions where stripe rust has been reported (i.e. County of Lethbridge) may be at an increased stripe rust risk, especially for winter wheat crops.
2. Texas-Oklahoma corridor – Currently, there is very limited leaf and stripe rust development in this corridor. Moreover, as the Texas and Oklahoma winter wheat crops continue to finish maturing and are harvested, this region no longer represents a significant source of cereal rust inoculum for movement into the Prairie region. In addition, there were a relatively low number of recent wind trajectories from this area for most prairie locations. Temperatures have been 2-3C above normal in southern Alberta, and most of Saskatchewan and Manitoba. In southcentral Alberta to the Peace River region in Alberta, temperatures have been normal to slightly below normal. Rainfall amounts were greatest in AB and southern/east-central SK, while eastern and southern Alberta, central to western Saskatchewan and most of Manitoba, except the SE corner had minimal amounts of rainfall. Winter wheat crops are progressing towards head emergence with some starting to flower, while there are generally early stages of Prairie spring wheat development ranging from the two leaf to tillering stages. Thus, as of June 15, 2020 the risk of leaf and stripe rust appearance from the Texas-Oklahoma corridor is limited and scouting for these diseases is not urgent.
3. Kansas to Nebraska corridor – Currently, there is some stripe rust development in Kansas, while there continue to be reports of stripe rust at low levels in Nebraska. Moreover, there were a relatively low number of recent wind trajectories from this area for most prairie locations. Temperatures have been 2-3C above normal in southern Alberta, and most of Saskatchewan and Manitoba. In southcentral Alberta to the Peace River region in Alberta, temperatures have been normal to slightly below normal. Rainfall amounts were greatest in AB and southern/east-central SK, while eastern and southern Alberta, central to western Saskatchewan and most of Manitoba, except the SE corner had minimal amounts of rainfall. Winter wheat crops are progressing towards head emergence with some starting to flower, while there are generally early stages of Prairie spring wheat development ranging from the two leaf to tillering stages. Thus, as of June 15, 2020 the risk of leaf and stripe rust appearance from the Kansas-Nebraska corridor is limited and scouting for these diseases is not urgent. However, 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. 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. Currently, there have been two reports of the initial appearance of stripe rust on winter wheat on June 5 and June 16, 2020 in the County of Lethbridge in southern Alberta.