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Date: Wed 22 Jul 2009
Source: Government of Alberta Agriculture and Rural Development, 27 Jul 2009 issue of Agri-News [edited] <http://www1.agric.gov.ab.ca/$department/newslett.nsf/all/agnw15295>

Stripe rust alert for southern Alberta wheat

Stripe rust is a significant disease of both wheat and barley worldwide. In Alberta, since 2003 the incidence and severity has increased dramatically in some years. The fungus can over-winter in Alberta. However, the greatest risk is from air-borne spores from wheat in the US.

Infections were first observed in the Lethbridge winter wheat nurseries on 30 Jun 2009 and conditions have favoured secondary infection. Infections were noted in the spring wheat nurseries on 3 Jul 2009. The rainfall on 13 Jul 2009, in southern Alberta favours continued sporulation and secondary infection.

Upon landing on a suitable wheat plant, the spores produce fungal strands, which grow beneath the leaf surface and emerge within 10 days as a stripe on the leaf. If ideal conditions persist, released spores re-infect other portions of the plant and ultimately the entire crop and [other] crops both near and far. The rainfall in Lethbridge combined with cool days and cold nights have allowed the disease to progress with a number of repeating cycles since 30 Jun [2009].

There are a number of spring and winter wheat varieties that offer very good resistance to stripe rust. Rust may still occur on these varieties but they should not require protection with a fungicide. For some varieties, the stripe rust reaction is not known. Radiant, the most commonly grown winter wheat in the Lethbridge region, has adequate stripe resistance whereas the number 2 variety, Bellatrix, is very susceptible. A number of effective fungicides are available.

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[Stripe rust, also called yellow rust, of cereals is caused by the fungus _Puccinia striiformis_ var. _striiformis_. It causes yellow leaf stripes and stunting of plants with yield losses of 40 to 100 per cent. It affects wheat, some barley varieties, triticale, and a number of wild grasses. Spores are wind dispersed in several cycles during the cropping season. Grasses and volunteer crop plants may generate a "green bridge" providing inoculum for the next crop cycle. Disease management includes the use of resistant varieties, fungicide applications, and control of volunteer crops.

New stripe rust strains with increased virulence have been reported in recent years from Europe, North America, Australia, India, and are also suspected to emerge in China. New strains may also be involved in the increase of disease severity in recent years reported above for Alberta. Disease monitoring is important to recognise new pathogen strains, and continuous resistance breeding is required to keep ahead of pathogen adaption.

Maps
Canada:
<http://www.lib.utexas.edu/maps/americas/canada_pol_1986.gif> and
<http://healthmap.org/r/00bA>
Alberta:
<http://atlas.nrcan.gc.ca/site/english/maps/reference/provincesterritories/alberta/referencemap_image_view>

Pictures
Stripe rust on wheat leaf:
<http://utextension.tennessee.edu/fieldCrops/wheat/Wheat_photos/Wheat_StripeRust.jpg> 
and
<http://www.grdc.com.au/uploads/images/Stripe%20rust%20Colin%20Wellings%20ACRCP.JPG>
Stripe rust on wheat head:
<http://cril.cimmyt.org/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=950&g2_serialNumber=2>
Stripe rust on resistant and susceptible wheat cultivars:
<http://www.oznet.ksu.edu/path-ext/factSheets/wheat/Wheatimages/wheats1.jpg>

Links
Information on wheat stripe rust:
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>,
<http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0006/158964/stripe-rust-in-wheat.pdf>,
<http://pnw-ag.wsu.edu/smallgrains/Stripe%20Rust.html>, and
<http://www.oznet.k-state.edu/path-ext/factSheets/Wheat/Wheat%20Stripe%20Rust.asp>
Stripe rust management:
<http://www.grdc.com.au/uploads/documents/striperustmgt.pdf>  and
<http://www.ipm.ucdavis.edu/PMG/r730100511.html>
_P. striiformis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=427989>. 
- Mod.DHA]