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International Society for Infectious Diseases <http://www.isid.org>

Date: 8 September 2008
Source: Country News [edited]
<http://www.countrynews.com.au/story.asp?TakeNo=200809089950981>

Stripe rust outbreak

DPI [Department of Primary Industries] said an outbreak of stripe rust on grain crops in northeastern Victoria had the potential to heavily impact the volume of yields. Initial reports of the disease date back to July [2008] in the region, with crops in Cobram the most severely affected.

DPI plant pathologist Frank Henry said most wheat varieties in the northeast were being affected to some extent, but there had been no confirmation about which types of stripe rust were involved. "There is a lot of stripe rust inoculum in the system as there was a significant green bridge for it to inhabit," Mr Henry said.
"Conditions in Victoria are becoming ideal for stripe rust, which is why we're beginning to see it. Growers should be diligent in monitoring their crops for signs of stripe rust from this point forward."

While unsure of just how badly the northeastern region has been affected by the disease, Mr Henry has major concerns. "I'd say it would be fairly severe, but it depends on how good the control strategies are," he said. For fungicides to be most effective against stripe rust, they have to be applied before it's known whether or not crops are going to respond. With spring now upon us, this time of the year is critical in controlling any outbreak of stripe rust, with the disease most active in the September to November period.

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[Wheat stripe rust (also called yellow rust) is caused by the fungus _Puccinia striiformis_ var. _striiformis_ and occurs worldwide mostly in cooler climates. It causes yellow leaf stripes, stunting of plants, and reduces grain production with yield losses of 40 to 100 percent. It affects wheat, some barley varieties, triticale, and a number of grass species. Spores are wind dispersed in several cycles during the cropping season. The fungus needs living plants to survive between seasons. Grasses and volunteer wheat may generate a "green bridge" providing inoculum to infect new crops. Disease management strategies include the use of resistant varieties, fungicide applications, and control of volunteer wheat.

Outbreaks of the disease were reported earlier this year (2008) in New South Wales and Queensland, and a new very virulent strain affected wheat crops in South Australia in 2007. Pathogen strains in Australia are being monitored annually since 1973, and several pathotypes exist. For more information on the disease please see links and previous posts below.

Maps
Australia:
<http://www.ga.gov.au/image_cache/GA4073.jpg>
Victoria:
<http://www.ozhorizons.com.au/vic/map.htm>

Pictures
Stripe rust leaf symptoms on wheat:
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0> and
<http://utextension.tennessee.edu/fieldCrops/wheat/Wheat_photos/Wheat_StripeRust.jpg>
Stripe rust symptom comparison 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://pnw-ag.wsu.edu/smallgrains/Stripe%20Rust.html>,
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>, 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>
_P. striiformis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=427989>
Rust monitoring and information on pathotypes in Australia:
<http://www.agric.usyd.edu.au:8888/pbi/cereal_rust_reports_crr.htm> and
<http://www.agric.usyd.edu.au:8888/pbi/cereal_rust_surveys.htm> - Mod.DHA]