Wheat streak mosaic virus (WSMV) has recently been found in southern Alberta from Pincher Creek to Medicine Hat

Five wheat fields have been confirmed positive for Wheat streak mosaic virus (WSMV) in southern Alberta from Pincher Creek to Medicine Hat. WSMV is a pathogen that is endemic to Alberta and shows up occasionally in wheat and winter wheat crops, but rarely on barley. The last time Alberta had a WSMV outbreak was 2015 and 2016.

The virus is vectored by the wheat curl mite and the mite and virus don’t normally overwinter unless they find a “green bridge” host such as winter wheat or perennial grasses. Volunteer wheat is very often the source of outbreaks. Most of the positive fields in 2022 were the result of winter wheat volunteers or herbicide escapes.

If you suspect WSMV and need help confirming it, you can contact Alberta Agriculture, Forestry and Rural Development (Dr. Michael Harding and Dr. Jie Feng) to have a laboratory test performed.

michael.harding@gov.ab.ca or 403-362-1338

There are no in-season remedies or management tools, so when fields are infected early (tillering or earlier) they should be terminated. When fields are infected after heading, yield losses are usually minimal. There are no effective insecticides.

Tillage or swathing/baling is recommended, followed by glyphosate application. This prevents the mite migrating to neighboring crops. Grazing is not recommended.

Nitrogen fertilizer applications will increase mite numbers and the virus will spread more rapidly.

Successful management will depend on management of ‘green bridge’ hosts from 2022 to 2023. This can be done by delaying the seeding of winter wheat until after the spring crop has been harvested completely, and controlling volunteers in the spring.

More detailed information can be found at the links below. Or you can listen to the American Phytopathological Society Podcast (Plantopia) on WSMV:

https://www.plantopiapodcast.org/22

https://open.alberta.ca/dataset/479eefac-42ad-4cc7-8ece-f2b40125b267/resource/eac60351-b802-464a-9b53-10fa826219e3/download/1993-112-632-3.pdf

https://apps.msuextension.org/montguide/guide.html?sku=%20MT200911AG

https://extensionpublications.unl.edu/assets/pdf/ec1871.pdf

Wheat streak mosaic virus (WSMV) in southern Alberta, photo courtesy of Michael Harding, AFRED 

Wheat streak mosaic virus (WSMV) in southern Alberta, photo courtesy of Michael Harding, AFRED 

Wheat streak mosaic virus (WSMV) in southern Alberta, photo courtesy of Michael Harding, AFRED 

Regional occurrence of wheat streak mosaic virus of wheat, June 30, 2022, Michael Harding AFRED

Michael Harding, Crop Health Assurance Lead

Agriculture, Forestry and Rural Economic Development

Brooks, AB

 

 

Prairie Crop Disease Monitoring Network Quick Disease Reporter Tool (PCDMN QDRT): Mini Tutorial for reporting Prairie crop disease observations

On June 1, 2022 we launched the updated Prairie Crop Disease Monitoring Network Quick Disease Reporter Tool (PCDMN QDRT) for the 2022 growing season (https://prairiecropdisease.blogspot.com/2022/06/announcing-2022-launch-of-prairie-crop.html).  

This blog post and others regarding the PCDMN QDRT in 2021 and 2022 are now outdated as various updates have been done with the app.  These updates have been focused on addressing privacy concerns from farmers, crop consultants and others who may use the app as well as functionality.   The new tutorial can be found at this link (https://prairiecropdisease.blogspot.com/2023/05/prairie-crop-disease-monitoring-network.html), while the new QR code for the PCDMN QDRT app is as follows:

Acknowledgements

The Prairie Crop Disease Monitoring Network (PCDMN) would like to thank the Canadian Agricultural Partnership Integrated Crop Agronomy Cluster and associated funding bodies for their gracious financial support.

The PCDMN would also like to sincerely thank Matthew McBurney, Geomatics Specialist, and Ryan Tondevold, Head - Geospatial Data Management, Science and Technology Branch, Agriculture and Agri-Food Canada, for their gracious assistance regarding the development and implementation of the PCDMN QDRT. 

For further information on the app or if you are having trouble using it, please contact:

PDCMN – T. Kelly Turkington: kelly.turkington@AGR.GC.CA;

AAFC Geomatics – aafc.agri-geomatics-agrogeomatiques.aac@agr.gc.ca

2022 Cereal Rust Risk Report (June 21 to 27, 2022)

The latest Prairie PCDMN wind trajectory cereal rust risk report is available for download now at the following link: June 21 to 27, 2022 report.  

As of the week of June 21-27, 2022 the overall Prairie cereal rust risk assessments and need for in-crop scouting are as follows:

Pacific Northwest – There was a moderate number of wind trajectories that passed over the PNW region from June 21-27, 2022 and into the prairies, while key stages of crop development are occurring or starting to occur for both winter and spring wheat, respectively.  In terms of stripe rust development in the PNW there have been increasing reports of occurrence including in commercial fields.  Some Prairie regions where most trajectories ended up did receive more moisture from June 21-27, 2022 versus the Peace region areas between Calgary and Edmonton, and areas south of Saskatoon and west of Regina.  Thus, as of June 27, 2022, the risk of stripe rust appearance from the PNW is low to moderate, while scouting for this disease in the Prairie region should be considered for those locations that received increased trajectories and moisture, especially where stripe rust susceptible varieties are planted.

Kansas-Nebraska corridor – Currently there is limited leaf and stripe rust development in this corridor, a low number of recent wind trajectories from this area, while some moisture occurred in the central to eastern Prairie region.  Given these conditions, as of June 27, 2022, the risk of leaf and stripe rust appearance from the Kansas-Nebraska corridor is generally limited and scouting for these diseases in the Prairies is not urgent.

Scouting and risk assessment recommendations for cereal leaf spot diseases

2022 moisture conditions in many Prairie regions are shaping up to be conducive for the development of leaf spot diseases in barley and wheat.  Although crop rotation and variety resistance are useful strategies, rotations typically need to be at least two years between host crops.  In addition, the variety being grown may not have a disease resistance package that covers all leaf diseases.  As a consequence fungicide application becomes a key tool for managing cereal leaf disease risk. 

Scouting is key to identifying emerging cereal leaf disease issues and the need for one or more in-crop fungicide applications.  Initially when scouting for weeds, producers and consultants can note the presence and level of leaf disease.  This gives you a heads up in terms of a developing issue and the potential need to spray a fungicide as the crop progresses from stem elongation to flag and head emergence.  Although there may be interest in applying fungicide at a herbicide timing, research indicates it will likely be of limited value in terms of protection of upper canopy leaves.  

See:  

https://cdnsciencepub.com/doi/full/10.1139/cjps-2020-0318

https://www.tandfonline.com/doi/abs/10.1080/07060660409507174

https://cdnsciencepub.com/doi/10.4141/cjps-2014-364  

Barley 2-3 leaf stage

Exceptions occur with cereal rust diseases, especially stripe rust, where a herbicide timing application can be more useful.  This is likely due to the biotrophic nature (i.e. they derive nutrients from living host tissues) of the rust pathogens and that initial rust inoculum typically comes from outside the crop, especially for spring cereals.  In contrast, cereal leaf spot diseases (scald, net blotch, spot blotch, tan spot, septorias) are necrotrophic in nature (i.e. the derive nutrients from dead plant tissue), while initial inoculum typically comes from old crop residues in the same field where the crop is growing.  Fungicide movement to the rust pathogen in living host tissues may be more extensive versus through dead plant tissues in the case of necrotrophic leaf spot pathogens.  In addition, cereal leaf spot inoculum is continuously produced from old crop residues and thus can infect any new leaves produced immediately after spraying has occurred.  

Given the nature of fungicides, movement within plant is typically limited, but with more mobile actives they are typically xylem mobile and thus need to be applied directly to the plant tissues that need protection.  Finally, fungicides do not generally have good eradicant activity, especially on mature established infections that are already 1-2 weeks old.  Thus, fungicides may not kill the leaf spot pathogens in well-established infections, although they may suppress pathogen development and sporulation, but only for about 2-3 weeks. 

Stylized representation of fungicide movement within a leaf

Should producers decide to use fungicides at a herbicide timing, if the disease risk remains moderate to high, they will need to spray again from flag leaf emergence to just after head emergence to protect key upper canopy tissues. Keep in mind that as the number of in-season fungicide applications increases so does the risk of fungicide resistance development.  Thus, if producers need to spray fungicide in a crop more than once during the growing season they need to implement strategies to limit the risk of fungicide resistance development.  Only spray if needed, limit the number of applications, rotate actives, and use products with multiple modes of action.  Here are some great resources in relation to managing the risk of fungicide resistance.  

https://manageresistancenow.ca/disease/dfs-how-to-manage-fungicide-resistance-in-your-crops/

https://cropprotectionnetwork.org/web-books/fungicide-use-in-field-crops?section=44-fungicide-resistance

https://www.gov.mb.ca/agriculture/crops/guides-and-publications/pubs/guide-crop-protection-2022.pdf (see page 453)

https://publications.saskatchewan.ca/api/v1/products/77706/formats/87089/download (see page 453)

https://bluebook.print3connect.com/Store/Site/Layout/Custom.aspx  

As the crop moves towards flag leaf emergence, producers and consultants can use the extent of leaf disease development in the lower to upper canopy to gauge risk and fungicide need.  The absence or limited appearance of symptoms (e.g. <1% leaf area affected or so) in the lower to middle canopy would generally indicate a low risk and thus limited need for fungicide.  However, things can change as the crop moves towards head emergence, so it is important to scout again.  Following head emergence if moderate disease levels are observed in the lower to middle canopy (e.g. >5-10% leaf area diseased) there is likely an emerging risk and need to spray a fungicide to protect key upper canopy leaves where most of your yield comes from (https://www.albertawheatbarley.com/the-growing-point/articles-library/where-does-my-yield-come-from?setcommission=alberta-barley).

When scouting for cereal leaf diseases correct identification is critical.  A variety of issues may produce leaf symptoms that may be incorrectly identified as fungal leaf diseases  For example, general leaf yellowing is not indicative of the cereal leaf spots (e.g. tan spot and septoria in wheat, net blotch/scald/spot blotch in barley), but may reflect nutrient deficiencies, drought/heat stress or perhaps root disease issues.  Make sure the symptoms are actually caused by disease and not damage (burning, scalding, etc.) due to insect feeding, herbicides or foliar-applied fertilizers.  Physiological leaf spotting can be confused with cereal leaf spot symptoms and are typically related to chloride deficiency and sun damage.  For example, with sun damage in barley the most severe symptoms are on the upper canopy leaves, while chloride deficiency symptoms are found throughout the cereal canopy and may be associated with particular cereal varieties.  In contrast, cereal leaf spot symptoms generally follow a gradient, i.e. most severe in the lower canopy, but decrease as you move to the middle and upper canopies.

 

Here are some links to a PCDMN post on white flecking in wheat, and Twitter posts and a Montana State University alert from earlier this spring regarding differentiating physiological leaf spots from those caused by cereal leaf spot pathogens.

 

https://prairiecropdisease.blogspot.com/2022/06/unusual-symptoms-in-alberta-barley-and.html

 

https://twitter.com/UtaMcKelvy/status/1532032900790530048

 

https://apps.msuextension.org/mtagalerts/htmlalert.cfm?alert=14927

 

https://twitter.com/pcdmn/status/1531762399669362689

 

 

Diagrammatic representation of typical cereal leaf spot symptoms

Diagrammatic representation of leaf symptoms not typical of cereal leaf spot diseases

Here are some links to PCDMN resources for cereal leaf spot identification:

Wheat:

• Speckled leaf blotch
• Parastagonospora/Septoria leaf and glume blotch
• Tan spot
• Fusarium head blight
• Fusarium head blight seed infections
• Bacterial leaf streak
• Cereal rusts

Barley:

• Net-form net blotch in barley
• Spot-form net blotch in barley
• Scald in barley
• Spot blotch in barley
• Fusarium head blight
• Fusarium head blight seed infections
• Cereal rusts

The use of standard area diagrams can help in terms of determining the level of leaf spot development.  Here are some standard area diagrams showing 1, 5, 10, 25, and 50% of the leaf area affected with various leaf spot diseases in barley and wheat.  Note that symptoms of spot-form net blotch and spot blotch in barley can be difficult to distinguish without laboratory testing of plant samples.  In addition, differentiating tan spot from the septoria complex in wheat can be challenging even for experienced plant pathologists, and thus a lab diagnosis may be needed.  However, all cereal leaf spot diseases result in destruction of leaf tissues and thus affect grain yield and filling.  The goal should be correct identification of leaf spot disease issues and then assessment of the overall level, i.e. severity. 

It is important to put the level of disease into perspective.  Trace to low levels of leaf disease from tillering to head emergence = limited risk, and thus a fungicide may not be needed, and if used can result in negative net returns.  In contrast, if you notice significant levels of disease during weed scouting, and increased severity in the lower to middle canopy at flag leaf emergence (especially on the third leaf from the head), a fungicide may be needed prior to head emergence, i.e. at or just before flag leaf emergence.  If leaf disease levels are absent or limited during weed scouting and at flag leaf emergence, you may be able to delay and only use one in-crop fungicide application after head emergence to provide leaf disease control and fusarium head blight suppression.  Lastly, a producer may have significant leaf disease development at stem elongation to flag leaf emergence and are also concerned about fusarium head blight and post head emergence leaf spot development.  In this situation more than one fungicide application may be needed, i.e. around flag leaf emergence plus again after head emergence.  Keep in mind that when you need to use more than one fungicide application during the growing season, make sure to use strategies to limit the risk of fungicide resistance development.

Finally, keep in mind what the weather conditions are like as well as the disease resistance package in the cereal variety you are growing.  Moderate temperatures, frequent rainfall and heavy dews increase the risk, especially with varieties that are not resistant to disease.  In contrast, with warm dry conditions and where the soil and crop canopy are dry in the morning, the risk of leaf spot development is limited and a fungicide is likely not needed (see wet pants test below).  Fungicide response is generally greatest for cereal varieties that are susceptible to moderately susceptible.  In contrast, varieties that are moderately resistant to resistance are less responsive and may not need a fungicide application.  One caveat is that a typical crop may be faced with multiple leaf disease issues.  Although a variety may be resistant to one disease, it may be susceptible to other diseases, and thus a fungicide may be needed depending on weather conditions and in-season disease appearance.

Provincial cereal variety guides with disease resistance ratings:

https://edition.pagesuite.com/html5/reader/production/default.aspx?pubname=&edid=f43082bb-5e08-420e-82b4-a4fde6b83dba

https://publications.saskatchewan.ca/api/v1/products/103730/formats/131802/download

https://www.seed.ab.ca/wp-content/uploads/2021/12/cereals-dec21.pdf

2022 Cereal Rust Risk Report (June 14 to 20, 2022)

The latest Prairie PCDMN wind trajectory cereal rust risk report is available for download now at the following link: June 14 to 20, 2022 report.  

As of the week of June 14-20, 2022 the overall Prairie cereal rust risk assessments and need for in-crop scouting are as follows:

 Pacific Northwest – There was a larger number of wind trajectories that passed over the PNW region from June 14-20, 2022 and into the prairies, while key stages of crop development are occurring or starting to occur for both winter and spring wheat, respectively.  In terms of stripe rust development in the PNW there have been increasing reports of occurrence including in commercial fields.  The central to western Prairie region where most trajectories ended up did receive more moisture from June 14-20, 2022 versus the central to eastern Prairie region.  Thus, as of June 20, 2022, the risk of stripe rust appearance from the PNW is generally low to moderate, while scouting for this disease in the Prairie region should be considered for those locations that received increased trajectories and moisture.

Texas-Oklahoma corridor – Given limited leaf and stripe rust development in this corridor, a low to moderate number of recent wind trajectories from this area, and somewhat drier conditions, especially in the eastern Prairies, as of June 20, 2022, the risk of leaf and stripe 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 limited leaf and stripe rust development in this corridor, a low to moderate number of recent wind trajectories from this area, and somewhat drier conditions, especially in the eastern Prairies, as of June 20, 2022, the risk of leaf and stripe rust appearance from the Kansas-Nebraska corridor is generally limited and scouting for these diseases in the Prairies is not urgent.

Unusual symptoms in Alberta barley and wheat crops, June 2022

Over the last two weeks pathologists in Alberta received reports of white flecking on leaves in wheat (June 13, 2022) and barley (June 4 and 14, 2022).  The symptoms were not typical of fungal leaf spots including scald, net blotch, spot blotch in barley, or tan spot or the septoria complex in wheat.  Here are some images of the symptoms that were observed recently (note click each photo to enlarge):

Barley:

Photo of white flecking in barley courtesy of Brittany Turchyn, Territory Manager at Corteva Agriscience, Peace River, Alberta, June 17, 2022. Field was managed as barley (2022) seeded on barley stubble (grown 2021).

Photo of white flecking in barley courtesy of Brittany Turchyn, Territory Manager at Corteva Agriscience, Peace River, Alberta, June 14, 2022.  Field was managed as barley (2022) seeded on barley stubble (grown 2021).

Photo of white flecking in barley courtesy of T. Kelly Turkington, AAFC Lacombe and Lorne Campbell, Rahr Malting, Inc., central Alberta, June 16, 2022.

Photo of white flecking in barley courtesy of T. Kelly Turkington, AAFC Lacombe and Lorne Campbell, Rahr Malting, Inc., central Alberta, June 16, 2022.

Photo of white flecking in barley courtesy of T. Kelly Turkington, AAFC Lacombe and Lorne Campbell, Rahr Malting, Inc., central Alberta, June 16, 2022.

Photo of white flecking in barley growing in Sturgeon County on June 4, 2022, courtesy of Kristina Wormald (Polziehn), Axiom Agronomy.

Wheat:

Photo of white flecking in wheat courtesy of Ernie Nycholat, Manager Agronomic Solutions, Northern Alberta, east central Alberta, June 13, 2022.

Photo of white flecking in wheat courtesy of Ernie Nycholat, Manager Agronomic Solutions, Northern Alberta, east central Alberta, June 13, 2022.

Observations of white flecking in barley and/or wheat have been reported from the Peace region (Brittany Turchyn/Mark Johns, Corteva Agriscience), central Alberta (Lorne Campbell, Rahr Malting, Inc.; Ernie Nycholat, Nutrien, Inc.) and the Edmonton region (Kristina Wormald (Polziehn), Axiom Agronomy).

 

Following the sharp eye of Henry Klein-Gebbinck, pathologist AAFC Beaverlodge, and discussions of various pictures with Tyler Wist, AAFC Saskatoon, Jennifer Otani, AAFC Beaverlodge, and Hector Carcamo and Haley Catton, AAFC Lethbridge, it was concluded that the white flecking was due to feeding damage by the insect Trigonotylus coelestialium aka the rice-leaf bug or green-grass bug.  Apparently according to Tyler Wist these insects produce digestive enzymes that result in the whitish dead flecks on the leaves.  Jennifer Otani adds that all the Miridae or plant bugs are recognized for both physical and chemical damage.  This damage arises from their mouthparts and the chemical cocktail they inject into the host plant that facilitates the sucking or ingestion of phloem. Both the physical and chemical damage leads to chlorosis or abscission, but it varies by mirid species and host plant.  Note the plant structures they feed upon, and the tolerance or ability of the host plant to cope with whatever density and feeding levels may arise, can be crop specific.

 

Jennifer Otani also adds that based on some pictures taken June 17, 2022, from the Peace region courtesy of Brittany Turchyn, Territory Manager at Corteva Agriscience, Peace River, Alberta, grass bug nymphs were identified and were likely in the 3rd – possibly 4th instar owing to presence of wing buds on a number of the specimens in Brittany’s photos and their smaller size.  Overwintered eggs very likely laid on 2021 barley then hatched in spring 2022 to develop and feed on newly seeded 2022 barley.  Trigonotylus coelestialium is fairly commonly found in grasses grown for seed across the Peace River region, but there are 1-2 other closely related species that can also appear – sometimes as a complex in the same field.  Jennifer also indicated that green grass bugs are common although high densities aren’t typical, yet many species of grass bugs do well with heat – and we had a LOT of that last year. Species belonging to the genus (usually greenish) Trigonotylus, Stenodema, Leptoturna, (and more blackish) Capsus, Labops, and Irbisia are all genus in the Miridae family, commonly referred to as plant bugs. Some or all of these genus can occur in grasses grown across the whole Peace River region and they are associated with silvertop so this is a tip to watch any grasses being grown for seed.  However, the monitoring/management window in all grass species grown for seed is quickly coming to an end the week of June 17, 2022, across the south of the Peace River region  Jennifer indicated that field experiments are underway in 2022 to assess and compare silvertop levels in creeping red fescue grown for seed so hopefully helpful data can be collected.  An important management consideration for growers observing this type of damage now is to rotate affected 2022 cereal stands to a broadleaf crop in 2023.  The mirids described above overwinter as eggs or adults so grassy- or cereal-type stubble has the potential to harbor similar species in 2023  - just remember - all mirids are extremely difficult to predict from year to year.

More detailed information related to these insect genus and species can be found in the (2018) insect field guide located here: https://www.researchgate.net/publication/360496020_Field_Crop_and_Forage_Pests_and_their_Natural_Enemies_in_Western_Canada_Identification_and_Management

 

Or the (2009) Alberta Forage Manual located here: https://open.alberta.ca/dataset/077326082x/resource/17d48b63-90bd-49b4-ad88-78a618febcd9

 

Both these guides are available as free, downloadable and searchable PDF files.

Photos of green-grass bug nymphs courtesy of Brittany Turchyn, Territory Manager at Corteva Agriscience, Peace River, Alberta, June 17, 2022.

Photos of green-grass bug nymphs courtesy of Brittany Turchyn, Territory Manager at Corteva Agriscience, Peace River, Alberta, June 17, 2022.

Overall, the whitish flecks being observed in barley and wheat do not appear to be related to fungal leaf spot diseases and thus a fungicide application would not be beneficial.  Note the key time to assess the risk of cereal leaf diseases, especially for the upper canopy leaves, is as the crop is progressing from stem elongation to flag leaf emergence.  Further observations can be done around head emergence to assess leaf disease risk, while also accounting for the risk of fusarium head blight (FHB).  More information on these and other cereal diseases can be found at:  

Wheat:

• Speckled leaf blotch
• Parastagonospora/Septoria leaf and glume blotch
• Tan spot
• Fusarium head blight
• Fusarium head blight seed infections
• Bacterial leaf streak
• Cereal rusts

Barley:

• Net-form net blotch in barley
• Spot-form net blotch in barley
• Scald in barley
• Spot blotch in barley
• Fusarium head blight
• Fusarium head blight seed infections
• Cereal rusts

2022 Cereal Rust Risk Report (June 7 to 13, 2022)

The latest Prairie PCDMN wind trajectory cereal rust risk report is available for download now at the following link: June 7 to 13, 2022 report.  

As of the week of June 7-13, 2022 the overall Prairie cereal rust risk assessments and need for in-crop scouting are as follows:

Pacific Northwest – Although there were a larger number of wind trajectories that passed over the PNW region and into the prairies and early (spring cereals)-mid (winter cereals) stages of crop development, there is generally limited stripe rust development in the PNW, and somewhat drier conditions in large areas of the Prairies western regions.  Thus, as of June 13, 2022 the risk of stripe rust appearance from the PNW is generally limited and scouting for this disease in the Prairie region is generally not urgent.

Texas-Oklahoma corridor – Given limited leaf and stripe rust development in this corridor, a limited number of recent wind trajectories from this area, and somewhat drier conditions in large areas of the Prairies, as of June 13, 2022 the risk of leaf and stripe rust appearance from the Texas-Oklahoma corridor is limited and scouting for these diseases in the Prairie region is not urgent.

Kansas-Nebraska corridor – Given limited leaf and stripe rust development in this corridor, a limited number of recent wind trajectories from this area, and somewhat drier conditions in large areas of the Prairies, as of June 13, 2022 the risk of leaf and stripe rust appearance from the Kansas-Nebraska corridor is limited and scouting for these diseases in the Prairies is not urgent.

Mini Prairie rust risk update, June 7-13, 2022

Our PCDMN wind trajectory and weather update for June 7-13, 2022 is a bit delayed.  However, the overall Prairie rust risk for this period is low given generally limited rust development in source USA locations.  Stay tuned for further updates.

1.      Rust development in source USA locations, June 7-13, 2022:

a.       Pacific Northwest (PNW)

                           i.  A report from Dr. X. Chen, USDA ARS, Pullman, WA on May 12, 2022 indicated that limited stripe rust has been observed in most commercial fields surveyed in Washington State and Oregon (https://striperust.wsu.edu/2022/05/12/stripe-rust-update-may-12-2022/). There have been some reports of low levels of stripe rust in nurseries and a few commercial fields in Washington State and Oregon (Drs. X Chen, C. Hagerty, and C. Neely,  https://www.capitalpress.com/ag_sectors/grains/stripe-rust-begins-to-develop-in-pacific-northwest/article_adad3968-d238-11ec-9a92-ef9380ff3c6f.html; https://osu-wams-blogs-uploads.s3.amazonaws.com/blogs.dir/2823/files/2022/05/2022_May_Rust.pdf; https://twitter.com/WSUVarietyTest/status/1529914406770860033).  

                            ii.  The latest report from Dr. Chen as of June 2, 2022 (https://striperust.wsu.edu/2022/06/03/stripe-rust-update-june-2-2022/) indicates development of stripe rust in experimental fields with levels being severe on lower canopy leaves (these were artificially inoculated to screen for resistance).  However, limited rust has been observed in commercial fields that were surveyed.  Dr. C. Neely also reports stripe rust from variety trials in Washington State and recommends scouting for this disease (https://twitter.com/WSUVarietyTest/status/1533947400816955392).

                           iii.  Dr. Chen indicates that as of June 2, 2022 increased moisture and somewhat cooler temperatures in May and forecast for early- to mid-June will favour further stripe rust development.  Scouting of winter wheat is recommended as the crop approaches head emergence and anthesis.  If the % of plants infected or the area of leaf infection approaches 5% it is recommended to spray a fungicide, especially before anthesis.

                            iv.  On June 14, 2022, Dr. T. Murray, WSU, referenced Dr. Chen’s June 2, 2022 report and reports by Dr. C. Neely regarding observations of rust in screening nurseries, while Dr. Neely also reported spraying of susceptible winter wheat varieties in commercial fields in the Horse Heaven Hills region as a result of “rust buil-up” (https://twitter.com/WSUSmallGrains/status/1536766353125695488, https://smallgrains.wsu.edu/latest-stripe-rust-updates/).  Dr. Murray also suggests that stripe rust will likely continue to develop given rain and cool weather, and that although susceptible varieties may need fungicide if further rust development occurs, moderately to highly resistant varieties will probably not need fungicide. 

                           v.  As of June 13, 2022, there is currently a relatively 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 fungicide application is recommended prior to anthesis for winter wheat if the threshold of 5% (see above) is observed and at herbicide timing for spring wheat fields planted to susceptible to moderately susceptible varieties. 

 

b.       Texas/Oklahoma

                           i.  In April and May there were reports of leaf rust occurring in Texas and Oklahoma (in rust nurseries), while stripe rust was reported in Texas in rust nurseries and trace to higher (on susceptible varieties) levels were reported in some areas of Oklahoma ([CEREAL-RUST-SURVEY] Small Grains Disease Conditions in South and Central Texas as of April 6, 2022, Dr. A. Ibrahim; https://twitter.com/OSUwheatdisease/status/1524193946137546754, Cereal Rust Bulletin, Report No. 1, April 25, 2022 and No. 2, May 27, 2022; https://www.ars.usda.gov/ARSUserFiles/50620500/CRBs/2022%20CRB%20April%2025.pdf, https://www.ars.usda.gov/ARSUserFiles/50620500/CRBs/2022%20CRB%20May%2027.pdf). Levels in the rust nurseries appeared to be increased on susceptible varieties.  Stem rust was not reported in these regions.  Drought conditions have generally limited rust development in these regions.  As of June 12, 2022, 100% of the winter wheat crops have headed in Texas and Oklahoma (https://quickstats.nass.usda.gov/results/D8BA8D9A-73B5-368D-A053-59F56D6B5A87). Given drought conditions crop development in this region is likely advanced, while as of June 12, 2022 16 and 35% of the Oklahoma winter wheat crops and 23 and 60% of the Texas winter wheat are rated as being in poor or very poor condition, respectively (https://quickstats.nass.usda.gov/results/8EC285B3-F5A4-31A0-9C25-615C9BE31683). In Texas, 53% of the winter wheat has been harvested, while 32% of the Oklahoma crops have been harvested (https://quickstats.nass.usda.gov/results/0357A5AE-E5C1-3658-A849-8C6A71098F76).  As winter wheat crops mature and are harvested they no longer represent a potential source of rust inoculum for the Prairie region.

                           ii.  As of June 13, 2022 there is a low risk associated with the Texas/Oklahoma region being a significant source of stripe or leaf rust inoculum for dispersal into the Prairie region of Canada.

 

c.       Kansas/Nebraska

                           i.  Earlier reports for Kansas in May indicate no to limited observations of leaf and stripe rust (Dr. K. Andersen Onofre, https://eupdate.agronomy.ksu.edu/article_new/wheat-disease-update-may-4th-2022-493; https://twitter.com/KSUWheatDisease/status/1524047507994648578; https://cropwatch.unl.edu/2022/wheat-disease-update-may-19; Cereal Rust Bulletin, Report No. 1, April 25, 2022 and No. 2, May 27, 2022,  https://www.ars.usda.gov/ARSUserFiles/50620500/CRBs/2022%20CRB%20April%2025.pdf, https://www.ars.usda.gov/ARSUserFiles/50620500/CRBs/2022%20CRB%20May%2027.pdf; https://twitter.com/progressivwilde/status/1527284446185107456).  The lack of appearance of rust is likely due to warmer temperatures and drought. 

                           ii.  Dr. M. Guttieri, USDA Manhattan, KS reported on June 7, 2022 that cooler temperatures and rainfall have promoted some development of stripe rust in KS nurseries, but plants are moving toward ripening (https://twitter.com/Wheat_MaryG/status/1534274584920440834). Leaf rust was also reported on a susceptible line in KS on June 5, 2022 (Dr. Guttieri, https://twitter.com/Wheat_MaryG/status/1533491986665283585).  

                           iii.  Stripe rust in KS has also been reported at two locations as of June 2, 2022 (https://twitter.com/WheatBlitzer/status/1532488400166604801 and https://twitter.com/WheatBlitzer/status/1532462782234386442).

                           iv.  On June 3 and 8, 2022, KSU Wheat Pathology and Dr. E. De Wolf of KSU indicated that limited stripe rust has been observed, while low levels of leaf rust are occurring in a number of counties.  Overall, Dr. De Wolf indicates KS wheat disease levels are lower than the 10 year average (https://twitter.com/KSUWheatDisease/status/1532881820399828993, [CEREAL-RUST-SURVEY] Update on Wheat Rust in Kansas as of June 8, 2022, Dr. E. De Wolf, KSU). 

                           v.  On May 20 and June 10, 2022 Dr. Stephen Wegulo reported no observations of leaf or stripe rust in Nebraska (https://cropwatch.unl.edu/2022/wheat-disease-update-may-19; https://cropwatch.unl.edu/2022/wheat-disease-update-june-10).

                           vi.  As of June 13, 2022, there is a relatively low risk associated with the Kansas/Nebraska region being a significant source of stripe or leaf rust inoculum for dispersal into the Prairie region of Canada.  Depending on weather conditions and further rust development, this risk may increase over the next several weeks.  However, winter wheat is progressing towards maturity, especially in Kansas with 31% of the crop rated as mature and 81% starting to senesce (colour) as of June 12, 2022 (https://quickstats.nass.usda.gov/results/856125C6-D2CA-30BE-A6D9-79224DDDAB4F; https://quickstats.nass.usda.gov/results/CCAA354D-E0B6-3DA7-9F40-0777A9EE792F). As winter wheat crops mature and are harvested they no longer represent a potential source of rust inoculum for the Prairie region.

2.      Prairie rust observations:

a.  Currently, there are no reports of early season rust development in Prairie winter wheat, which would suggest potential overwintering, especially of stripe rust (personal communication: S. Waterman/S. Rehman, Olds College, Lacombe, R. Aboukhaddour, AAFC Lethbridge; and H.R. Kutcher, U. of S.).  On May 30, 2022, G. Brar with the University of British Columbia has reported natural stripe rust infections in winter wheat and barley plots at the UBC Campus (https://twitter.com/gurcharn_brar/status/1531327915236814848).  More recently in Alberta, R. Aboukhaddour reported on June 11, 2022 the first occurrence of stripe rust in a Lethbridge region screening nursery (https://twitter.com/ReemWheat/status/1535678439163764737).  In addition, on June 12, 2022 Dr. Brar reported further significant development of stripe rust in UBC nurseries in the Vancouver region (https://twitter.com/gurcharn_brar/status/1536144846544437248).  

 

3.       Prairie Crop Development, Weather Conditions, and Overwintering of Rust

a.  Winter wheat – Winter wheat continues to grow across the prairie region in late May to early June (https://open.alberta.ca/dataset/a7ad3687-1d97-43e4-90a9-66cef8845a68/resource/afa945bd-3ad6-4621-89db-486ca71b8d54/download/afred-itrb-alberta-crop-report-2022-06-07.pdf; https://publications.saskatchewan.ca/api/v1/products/118112/formats/135746/download; https://www.gov.mb.ca/agriculture/crops/seasonal-reports/crop-report-archive/pubs/crop-report-2022-05-31.pdf; https://www.gov.mb.ca/agriculture/crops/seasonal-reports/crop-report-archive/pubs/crop-report-2022-06-07.pdf). In Saskatchewan, winter cereal crops are reported to be in the jointing/stem elongation stage although some crops are progressing into the shot blade stage of development (https://publications.saskatchewan.ca/api/v1/products/118112/formats/135746/download).  Winter wheat in Manitoba is reported to be in the stem elongation/jointing to the booting stage of development although in eastern regions some crops have started heading out.  In some areas concerns regarding wet conditions and leaf spots has led to fungicide application around the flag leaf to head emergence stages (https://www.gov.mb.ca/agriculture/crops/seasonal-reports/crop-report-archive/pubs/crop-report-2022-06-14.pdf).

b.  Spring wheat – Generally, spring wheat is at the seedling to 3-4 leaf and tillering stage of development depending on province and region (https://publications.saskatchewan.ca/api/v1/products/118112/formats/135746/download; https://www.gov.mb.ca/agriculture/crops/seasonal-reports/crop-report-archive/pubs/crop-report-2022-06-14.pdf).