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[1]
Date: Wed 14 May 2008
Source: Agriculture Online [edited]
<http://www.agriculture.com/ag/story.jhtml?storyid=/templatedata/ag/story/data/1210791746847.xml>

Leaf rust is starting to pop up in hard red winter wheat in parts of the Plains where harvest is just weeks away. Some varieties in Oklahoma test plots are showing high susceptibility to the disease, according to Oklahoma State University Extension wheat pathologist Bob Hunger. But, it's been held to areas where the weather's favored leaf rust's development. The disease thrives in wet.

"One report I received from near Hinton, Oklahoma indicated that leaf rust in unsprayed fields of Jagger was covering the flag leaves,"
Hunger says. "Similar reports of severe leaf rust have come from the experiment station at Lahoma." Not all varieties are affected by leaf rust, however. Hunger says the varieties showing highest levels of susceptibility right now are Jagalene, Jagger, and Lakin.

"The earlier leaves are lost, the more severe the yield loss. Losses may vary depending on the variety's ability to fill from the stem, glumes, and awns," Kansas State University Extension plant pathologist Robert Bowden says. "Susceptible varieties can be protected from rust with foliar fungicides. Although systemic fungicides can give very good control of leaf rust, they are relatively expensive, and use is limited to fields with high yield and disease potentials."

In diagnosing leaf rust in the field, Bowden says to look for orange pustules on the leaf surface, sometimes surrounded by a "narrow yellow or white halo. When rust severity is high, field scouts may notice the orange dust on hands and clothing," he adds. "Leaf rust typically occurs uniformly across a field. In overwintering locations, it is most severe on the bottom leaves. When it blows in from distant fields, it will be most severe on upper leaves."

[Byline: Jeff Caldwell]

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[2]
Date: Sun 11 May 2008
Source: The Hays Daily News [edited]
<http://www.hdnews.net/Story/Campbell051108>

Currently, leaf rust has been found at low levels at the Hays Agricultural Research Center. However, reports from the south-central part of Kansas and Oklahoma are seeing leaf rust increasing significantly, especially with the moist conditions they are experiencing. It is critical to scout fields routinely a minimum of twice a week until the crop has fully headed.

Leaf rust favors warmer weather with some humidity. Currently, the weather conditions in Ellis County and the area are very favorable for a possibly huge outbreak of leaf rust within the next week or so.
The most effective fungicide sprays are applied between flag leaf emergence through heading. Yield responses can be greater than 20 percent in fields where leaf rust arrives prior to flowering.

Some leaf rust was observed even on Post Rock, which has a high resistance rating for leaf rust, so all wheat varieties and fields should be scouted often for the detection of leaf rust.

[Byline: Erick De Wolf]

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[Leaf rust, also called brown rust, on wheat is caused by the fungus _Puccinia recondita_. It reduces the photosynthetic potential of the plant and can cause serious yield losses of over 40 percent in individual fields. Symptoms include brick-red pustules on leaves, stems, and later on heads. As the crop ripens, spores are produced.
Infection of the host can occur in as little as 4 hours in favourable conditions. Epidemic severity increases exponentially over time and may appear to "explode" suddenly during favourable weather. The fungus can only survive in living leaf tissue and overwinters on volunteer wheat, barley, and certain wild grasses. It is not soil-borne and spores are spread by wind and mechanical means.
Disease management relies mainly on timely fungicide applications and choice of crop cultivars.

Maps
USA:
<http://www.mapsofworld.com/usa/usa-road-map-enlarge-view.html> and <http://healthmap.org/promed?v=40,-97.6,4>
US states:
<http://www.census.gov/geo/www/us_regdiv.pdf>

Pictures of leaf rust on wheat:
<http://www.hgca.com/hgca/wde/IMAGES/brown%20rust1.JPG>,
<http://www.hgca.com/hgca/wde/diseases/Brown%20rust/brstd.html> and <http://www.hgca.com/hgca/wde/diseases/Brown%20rust/brstaxil.html>

Links
Additional news stories:
<http://www.dodgeglobe.com/opinions/x914625374>  and
<http://www.tradingmarkets.com/.site/news/Stock%20News/1516349/>
Information on wheat leaf rust:
<http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=1138>,
<http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp>
and
<http://www.hgca.com/hgca/wde/diseases/Brown%20rust/Brhost.html>
_P. recondita_ taxonomy and synonyms:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=145187>.  - Mod.DHA]

[see also in the archive:
Fungal diseases, cereals - UK, Ireland: update 20080428.1460 Fungal diseases, wheat - Canada, USA 20080427.1454 Fungal pathogens, wheat - UK (England) 20080319.1055
2007
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Fungal pathogens, wheat - United Kingdom: new races 20070523.1652 Rust diseases, bean & wheat - UK: alert 20070512.1515
2006
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Leaf rust, wheat - Russia (Irkutsk) 20060815.2287
2005
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Leaf rust, wheat, resistance change - India 20051201.3462 Leaf rust, Septoria spp., wheat - Kazakhstan: corr. 20050825.2509 Leaf rust, Septoria spp., wheat - Kazakhstan 20050823.2488

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