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[1] Wheat mosaic virus - Oregon
[2] Barley yellow dwarf virus, grasses - Oregon
[3] Triticum mosaic virus, wheat - Kansas


[1] Wheat mosaic virus, Oregon
Date: Sat 12 Apr 2008
Source: The Walla Walla Union-Bulletin [edited]
<http://www.union-bulletin.com/articles/2008/04/12/local_news/0804133wheatmosaic.txt>

Wheat mosaic virus confirmed, appears to have spread

The focus of a field trip was soil-borne _Wheat mosaic virus_.
Although the yellow patches had been seen in isolated fields for several years, the virus was only recently identified as the cause.
This year [2008] outbreaks appear to have spread. The discovery was announced by Matt Weber and Marshal McKinley, agronomists with the McGregor Company.

Among the group were Tim Murray, Washington State University, and Richard Smiley, Oregon State University. "This is an unusual disease, transmitted by a soil-borne fungus," Murray said. While not new, the virus has been rarely identified in the Pacific Northwest. Murray said the main control used elsewhere is disease-resistant varieties of wheat. A priority will be identifying which [wheat] strains are most resistant. There are very few other ways to control the disease, Smiley said. Sanitizing equipment by cleaning off soil is one method, he said.

Murray and Smiley said the virus is easy to confuse with another disease, _Wheat streak mosaic virus_. "There's probably about 30 viruses that affect wheat, but it takes a biochemical analysis to differentiate them," Smiley said. The cool, relatively damp conditions this spring [2008] appear to have triggered more outbreaks. Warmer weather, generally above 70 deg F [21 deg C], slows and eventually stops the disease development, confining symptoms to lower leaves.

Murray and Smiley also said it is possible the infection has been in Walla Walla County for some time, but that the right conditions hadn't occurred until recently to bring the virus out. "It's going to vary from year to year," Murray said. "We're in a year now where we're seeing a good expression of the disease."

[Byline: Andy Porter]

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[2] Barley yellow dwarf virus, grasses - Oregon
Date: Fri 4 Apr 2008
Source: Capital Press [edited]
<http://www.capitalpress.info/main.asp?SectionID=67&SubSectionID=618&ArticleID=40552&TM=8046.933>
[Subscription required]

Grain virus finding home in valley's grass seed crops

As wheat acres soar in the Willamette Valley, so do concerns over a virus associated with wheat that is infecting grass seed plants. Researchers hope to develop a strategy to deal with _Barley yellow dwarf virus_ [BYDV] in perennial ryegrass and tall fescue seed crops. Western Oregon scientists attribute at least part of the influx to a
dramatic increase of wheat acres in the valley. BYDV causes a common disease in wheat and is a constant concern in areas where wheat is widely grown. Corn also is a host for the virus, but corn is symptomless. The virus is spread by aphids.

OSU [Oregon State University] Extension agent Tom Silberstein said this week he's been seeing extensive evidence of the virus in grass seed in recent days. "We're seeing a lot of fields with yellow patches and unthrifty plants," Silberstein said. He estimates that at high levels the virus, which shrivels plant heads, can reduce yields
as much as 20 percent. Crop scientists are hoping to answer several questions, such as whether certain varieties are more susceptible; why the virus is showing up more often in 2nd-year fields; whether infection occurs in the fall previous to the following year's crop or in the previous spring and summer; and what are effective control
strategies.

In wheat, researchers advise growers to delay planting to give cold fall weather a chance to reduce aphid populations. In grass seed, however, where fields often stay in production between 3 and 5 years, planting-date control strategies often are ineffective. Adding to concerns in grass seed is that once a plant is infected, it is
infected for life. That gives aphids plenty of opportunity to feed on the plant and transmit the disease to another plant.

Chemical control strategies available to growers include lowering aphid populations in a field or deterring them from entering a field, Silberstein said. But chemical control strategies often are
ineffective.

[Byline: Mitch Lies]

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[3] Triticum mosaic virus, wheat - Kansas
Date: Tue 25 Mar 2008
Source: Agriculture Online [edited]
<http://www.agriculture.com/ag/story.jhtml?storyid=/templatedata/ag/story/data/1206462778770.xml>

Virus adds new wrinkle to wheat disease picture

First found by Kansas State University researchers in 2006, a newly discovered virus affecting wheat was officially recognized and named Triticum mosaic virus [TriMV] in 2007. TriMV is now considered one of 3 diseases affecting wheat in approximately the same manner -- the other 2 being _Wheat streak mosaic virus_ [WSMV] and high plains disease [HPD, probable virus], says Erick DeWolf, K-State Research and Extension plant pathologist. All of these diseases are vectored, with varying degrees of efficiency, by the wheat curl mite. In addition, the disease symptoms of all 3 diseases are virtually identical, he adds.

Many aspects of TriMV remain largely unknown at this point, including varietal reaction, distribution, and yield loss potential. "Although there has been no conclusive varietal screening for TriMV alone yet, it is known that RonL is susceptible," DeWolf says. RonL is the 1st variety to have true genetic resistance to WSMV, at least under cool
temperature conditions. If RonL shows WSMV-like symptoms, and temperatures have been cool, then TriMV should be suspected.

At this point, there is no reason for producers to be unduly alarmed by the detection of this new virus disease on wheat, DeWolf says. "TriMV may have been present at low levels for many years, and was only now detected when disease symptoms appeared on RonL," he says. "It is also possible that TriMV is new to the High Plains, but there is no way to know for sure." Because TriMV is vectored in the same manner as WSMV and HPD, producers should take the same preventive measures: control volunteer wheat and plant after the Hessian fly-free date, DeWolf says.

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[Soil-borne wheat mosaic disease

Wheat mosaic disease was first reported in 1919 in the central United States, and _Wheat mosaic virus_ (WMV, genus _Furovirus_) was later identified as the cause making it one of the earliest known wheat viruses and the 1st to be characterized as soil-borne. The disease now occurs in many countries from various parts of the world.
Normally only autumn-sown (winter) wheat develops symptoms, although spring wheat is also susceptible. Symptoms range from mild green to prominent yellow leaf mosaics (mottling). Stunting can be moderate to severe. Rising spring temperatures slow and eventually stop disease development.

WMV is transmitted by the soil-inhabiting fungus _Polymyxa graminis_ and can also be spread with contaminated soil, by water, and mechanical means. It is not seed-transmitted. For reasons not understood, the virus sometimes spreads more rapidly and over longer distances than can be explained by soil or water movement. Resistant wheat cultivars are available, and so far no resistance-breaking WMV strains have been reported.

Barley yellow dwarf disease

Barley yellow dwarf (BYD) occurs worldwide and is the most destructive of virus diseases of wheat. Grain yields may be reduced by one third. It attacks a wide range of grass species (_Gramineae_) including wheat, oats, rice, maize, rye, and barley. Oats are usually considered more susceptible than wheat. Symptoms include leaf
discolouration from yellow to purple (depending on the host species), stunting, reduced tillering, and empty seed heads. Plants infected in autumn may not survive the winter or show severe symptoms when growth resumes. Diseased plants often occur in circular patches within the field, which are associated with colonisation by the aphid vectors.

BYD viruses have now been split into several species in the family _Luteoviridae_ (mostly in the genus _Luteovirus_) and are differentiated by their ability to be transmitted by various aphid species and their virulence on a selected variety of oats. They cannot be transmitted by seed, pollen, or mechanical means and cannot
survive in stubble or in the soil. Volunteer cereal plants or grassy weeds may serve as pathogen reservoirs. Disease management includes use of resistant cultivars and control of the aphid vectors.

Triticum mosaic virus

Triticum mosaic virus (TriMV) is an as yet unclassified virus in the family _Potyviridae_. It was discovered very recently (2006) in the Kansas Hays area in wheat cultivars developed for their resistance to _Wheat streak mosaic virus_ (WSMV). It is spread by the wheat curl mite _Aceria tulipae_. For more information on this mite and _Wheat
streak mosaic virus_ see ProMED-mail post no. 20070928.3211.

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
WMV leaf symptoms:
<http://www.apsnet.org/education/LessonsPlantPath/soilborneWheat/images/fig05.jpg> 
and
<http://www.defra.gov.uk/planth/graphics/2006/sbcmv.jpg>
Wheat field with patch affected by WMV:
<http://www.ipm.uiuc.edu/diseases/series100/rpd102/102-2.gif>
WSMV leaf symptoms:
<http://www2.dpi.qld.gov.au/images/8658.jpg>
Healthy and BYD-affected wheat plants:
<http://www.ent.iastate.edu/imagegal/plantpath/wheat/ydwarf/0093.04ydwarfmv.html> 

Wheat field with BYD symptoms:
<http://www.ent.iastate.edu/images/plantpath/wheat/ydwarf/0093.10ydwarfwheat.jpg> 

Links:
Additional news story on WMV outbreak:
<http://www.eastoregonian.info/main.asp?SectionID=13&SubSectionID=48&ArticleID=76151&TM=38366.73>
Soil-borne wheat mosaic disease information:
<http://www.defra.gov.uk/planth/pestnote/soilborne.htm>,
<http://www.ipm.uiuc.edu/diseases/series100/rpd102/index.html#symptoms> and
<http://www.ipm.uiuc.edu/diseases/series100/rpd102/index.html#cycles>
WMV taxonomy and description:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.027.0.01.001.htm>
_P. graminis_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=266382>
BYD fact sheets:
<http://ohioline.osu.edu/ac-fact/0005.html>,
<http://www.ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=923> 
and
<http://ipm.ppws.vt.edu/stromberg/smallgrain/biology/wydwarf.html>
Genus _Luteovirus_ taxonomy and species list:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.039.0.01.htm>
Triticum mosaic virus preliminary taxonomy and description:
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-5-0808?journalCode=pdis>
Family _Potyviridae_ taxonomy:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.057.htm>
List of wheat viruses:
<http://www.apsnet.org/online/common/names/wheat.asp>  and
<http://www.fao.org/DOCREP/006/Y4011E/y4011e0o.htm>
Review of wheat viruses:
<http://muextension.missouri.edu/explore/agguides/crops/g04318.htm>. - Mod.DHA]

[see also in the archive:
2007
----
Barley yellow dwarf virus - UK: alert 20071102.3561
Wheat streak mosaic virus - Australia (TAS) 20070928.3211
Barley yellow dwarf virus & stem rust, cereals - Kenya 20070705.2132
Barley yellow dwarf virus, wheat - USA (IN, NE) 20070531.1758
Wheat diseases - USA (KS): crop loss 20070518.1574
2006
----
Triticum mosaic virus, wheat - USA (KS): 1st Report 20061102.3143
2003
----
Cereal viruses, oat, barley - USA (Alaska) 20030405.0832
2001
----
Cereal viruses, wheat - Uzbekistan 20011103.2723
Cereal viruses, barley, wheat - Tunisia 20010829.2049
2000
----
Wheat & rye mosaic viruses, soilborne 20000331.0483
1999
----
Crop diseases - Canada (Manitoba) 19990816.1417
Barley Yellow Dwarf virus alert - New Zealand 19990708.1140]