ProMED

Source: Farmers Weekly [summ. Mod.DHA, edited]
https://www.fwi.co.uk/arable/crop-management/disease-management/why-stem-rust-could-be-back-in-wheat-crops-and-what-to-do-about-it

Stem rust is on the brink of re-establishing itself in UK fields. Conditions have become more conducive to the disease, with warmer summers, a move to later-maturing varieties of wheat, and more spring cropping in rotations. Stem rust was once common in western Europe, with frequent epidemics. However, since the last big epidemic in 1955, there were several decades when it had not been seen in the UK.

In 2013, the UK saw its first recorded case in nearly 60 years. Since then, stem rust has been observed at several locations, generally at low incidence. But in summer 2022 it was the most widespread since 1955. Sites in at least 12 different English counties and Wales are known, including in recommended list trials.

With no evidence of local infection from barberry bushes, it is thought that the disease is moving long distances on wind from other parts of the world as urediniospores. Shortly before stem rust reports started to come in, there was a particularly big Saharan dust cloud moving north, which could have picked up the spores from North Africa or anywhere along the route through Europe to the UK.

Another recent change is that up to 2021, all UK outbreaks were caused by a single race of stem rust [Digalu strains; ProMED post 20180219.5638265], but researchers are now seeing more races in the UK.

[byline: Richard Allison]
--
communicated by:
ProMED

[Wheat stem rust (_Puccinia graminis_) has been reported to cause overall yield losses of up to 80%, but some fields are totally destroyed. Barley is also susceptible to this pathogen. Stem rust spores are spread by wind and with infected straw or other contaminated materials. The fungus can survive between seasons on some grasses or volunteer wheat, generating a "green bridge". Alternatively, it can also produce hardy teliospores to infect members of the genus _Berberis_ (barberries) in the next season, which then serve as a source of crop inoculum. Barberry is suspected to have given rise to a recent outbreak of stem rust in barley in the UK (ProMED post 20191008.6714735).

Disease monitoring is important so that timely action can be taken to limit the spread of the pathogen as well as build-up of inoculum. Disease management may include fungicide applications, control of volunteer wheat and berberis reservoirs, as well as resistant varieties, if available. Resistance breeding programmes have been set up by several countries and international groups. However, new fungal races with increased virulence are emerging frequently. Recombinants of different races would pose a high risk of becoming even more aggressive than the parents. Of the more than 50 known wheat resistance genes to stem rust, only very few are currently left that have not been overcome by a stem rust race.

Stem rust is currently being considered a re-emerging disease in Europe. After its long absence from the region, many wheat varieties planted there now are susceptible. In the UK, the teliospore host barberry has been planted increasingly as habitat for the endangered barberry carpet moth and is suspected to have given rise to a recent outbreak of stem rust in barley (ProMED post 20191008.6714735).

Maps
UK:
https://www.worldometers.info/img/maps/unitedkingdom_physical_map.gif
UK regions and counties:
https://tinyurl.com/ml5ggkx
Europe, overview:
https://mapofeurope.com/wp-content/uploads/2018/03/europe-political-map.jpg

Pictures
Stem rust symptoms on wheat:
https://www.rothamsted.ac.uk/sites/default/files/WSR_at_important_Flag_Leaf_stage_credit_Robert_Park_University_of_Sydney-TEXT_1.jpg,
https://www.agric.wa.gov.au/sites/gateway/files/styles/original/public/stem%20rust%20head%20infection%20closeup%20wheat_2.jpg,
https://rusttracker.cimmyt.org/wp-content/uploads/2017/02/StemRustSisily.png,
https://www.graincentral.com/wp-content/uploads/2017/12/Stem_rust_field_credit_Robert_Park_University_of_Sydney.jpg,
https://crop-protection-network.s3.amazonaws.com/articles/photos/Stem-rust.-Burrows.-July-2009-7.jpg and
https://kggfradio.com/assets/images/blogs/2019/wheat_stem_rust.png
Stem rust on resistant vs. susceptible wheat cultivars:
https://www.cimmyt.org/content/uploads/2019/06/wheat2.jpg and
https://assets.irinnews.org/s3fs-public/styles/responsive_large/public/images/201010281129340750.jpg
_P. graminis_ symptoms on barberry leaves:
https://pnwhandbooks.org/sites/pnwhandbooks/files/plant/images/barberry-berberis-spp-rusts/dsc0008.jpg and
https://c8.alamy.com/comp/XAK70Y/common-barberry-european-barberry-berberis-vulgaris-leaves-with-puccinia-graminis-stem-rusts-germany-north-rhine-westphalia-XAK70Y.jpg

Links
Information on wheat stem rust:
https://www.apsnet.org/edcenter/disandpath/fungalbasidio/pdlessons/Pages/StemRust.aspx,
https://www.agric.wa.gov.au/mycrop/diagnosing-stem-rust-wheat,
https://www.plantwise.org/knowledgebank/factsheetforfarmers/20127801775,
https://2blades.org/projects-and-technology/projects/1/,
https://guide.utcrops.com/wheat/wheat-disease-identification/diseases-affecting-leaves/stem-rust/,
http://www.ars.usda.gov/Main/docs.htm?docid=9910 and via
http://www.ars.usda.gov/Main/docs.htm?docid=14649
Stem rust disease cycle:
https://i.pinimg.com/originals/e2/fb/35/e2fb352fb297508257dcfe7606db8334.png
Resistance breeding:
https://doi.org/10.1094/PHYTO-08-20-0325-R and
https://phys.org/news/2021-04-wild-barley-jordan-key-stem.html
Re-emergence of wheat stem rust in Europe (reviews):
https://doi.org/10.1038/s42003-019-0294-9 and
https://doi.org/10.1038/s42003-018-0013-y
Stem rust strains nomenclature and worldwide distribution via:
https://rusttracker.cimmyt.org/?page_id=7
_P. graminis_ taxonomy and synonyms:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=159822 and
http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=159822
Wheat rusts overview, including epidemiology and spore types:
http://www.fao.org/3/y4011e/y4011e0g.htm
Global Rust Initiative:
https://bgri.cornell.edu/
- Mod.DHA]