Wind trajectory and cereal rust risk assessment and need for in-crop scouting in the Prairie region, June 2-8, 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 (3-7) with reverse trajectories from the PNW included: Beiseker (4), Lethbridge (7), and Olds, AB (4); Gainsborough (5) and Regina (4), SK; and Brandon (3), Carman (3), Dauphin (4), Russell (3) and Selkirk (3), MB. Manning, Provost, Rycroft and Wanham, AB, did not have any reverse trajectories originating from the PNW over the period of June 2-8, 2020, with the remaining locations having 1-2 days with events (Table 1). Currently there appears to be relatively low levels of stripe rust development in the PNW, although this may change over the next week or so. Temperatures have been relatively cool in the western Prairie regions with somewhat higher temperatures in the central to eastern Prairies. Dry conditions have occurred in the Peace region, some areas of central and southern Alberta and in southern to eastern Saskatchewan and most areas of Manitoba, except the southeast. Winter wheat crops are progressing towards flag leaf emergence to booting, while there are generally early stages of Prairie spring wheat development. Thus, as of June 8, 2020 the risk of stripe rust appearance from the PNW is somewhat limited and scouting for this disease is not urgent. However, locations with 3-7 reverse trajectory events from the PNW may be at a slightly increased stripe rust risk, especially for winter wheat crops. As of June 3 and 5, 2020 there have been reports of stripe rust in western Idaho and southern Alberta. 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 lookout for stripe rust, especially in winter wheat fields in southern Alberta.
2. Texas-Oklahoma corridor – Currently, there is limited leaf and stripe rust development in this corridor. Moreover, there were a relatively low number of recent wind trajectories from this area for most prairie locations. Temperatures have been relatively cool in the western Prairie regions with somewhat higher temperatures in the central to eastern Prairies. Dry conditions have occurred in the Peace region, some areas of central and southern Alberta and in southern to eastern Saskatchewan and most areas of Manitoba, except the southeast. Winter wheat crops are progressing towards flag leaf emergence to booting, while there are generally early stages of Prairie spring wheat development. Thus, as of June 8, 2020 the risk of leaf and stripe rust appearance from the Texas-Oklahoma corridor is limited and scouting for these diseases is not urgent. Finally, crops in Texas and Oklahoma are generally at maturity with harvesting occurring in many areas in Texas and Oklahoma, thus this region is of limited concern as a source or rust inoculum.
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 relatively cool in the western Prairie regions with somewhat higher temperatures in the central to eastern Prairies. Dry conditions have occurred in the Peace region, some areas of central and southern Alberta and in southern to eastern Saskatchewan and most areas of Manitoba, except the southeast. Winter wheat crops are progressing towards flag leaf emergence to booting, while there are early stages of Prairie spring wheat development. Thus, as of June 8, 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 have been initial 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 lookout 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 has only been one report of stripe rust on winter wheat and this was from southern Alberta on June 5, 2020.
