May 15, 2006
From: ProMED-mail<promed@promedmail.org>
Source: abc.net.au [edited]
<http://www.abc.net.au/news/newsitems/200605/s1635253.htm>

Western Australia's Department of Agriculture has confirmed several cases of wheat streak mosaic virus in the southern wheatbelt: 2 cases have been confirmed in the Esperance area and one in Kondinin.

The seed-borne disease can cause extensive damage to crop yields, although it is too early to know what damage may result. Minister for Agriculture Kim Chance says while the discovery is regrettable, it is now a case of dealing with it. "There is absolutely nothing we can do about it," he said. "That is a great concern, we now have it and we'll move to deal with it. I can remember going through this same process with stripe rust, we hoped we were never going to get it but eventually it did turn up."

Mr. Chance says it is inevitable the disease will spread.

"It's one of those things that you know is inevitable, you know that some time it's going to get here through one means or another, there's very little you can do to keep them out,"
Mr. Chance said.

--
ProMED-mail
<promed@promedmail.org>

[The cereal crop plant wheat, _Triticum aestivum_ L. subsp. _aestivum_, develops symptoms of the disease wheat streak mosaic when infected by wheat streak mosaic virus (genus: Tritimovirus, family: Potyviridae, WSMV). It can also infect barley, maize, oats and rye and some pasture and weed grasses. The virus is transmitted by the eriophyid wheat curl mite (_Aceria tosichella_). WSMV causes severe disease in some winter wheat crops in the Great Plains of North America, with average losses of 3 percent. There is one report (Argentina, 20040922.2614) from South America. It occurs throughout the Mediterranean Basin at low incidence and is reported from Eastern Europe.

The first detection of WSMV in Australia was in southern Queensland and South Australia in 2003 (20030417.0941 and 11 other postings that year, all of which are included in the final posting, 20030603.1354).
The high level of concern at that time is clear in these postings and in the first 4 links, all to Australian reports, listed below. It was subsequently reported in 2005 in New South Wales (20051029.3159), and that outbreak was quite severe in individual fields (paddocks) of wheat. While the stunted, yellowed plants flowered and set seed, they produced only very small and shriveled grain. Badly affected paddocks were not harvested. An estimated 7000 hectares were affected there in 2005, 1000 severely. Monetary losses in 2005 were estimated at approximately Aus $2 million (USD 1.5 million). Work in Australia has demonstrated that WSMV is seed-transmitted in wheat, but it is not clear what part this plays in the overall epidemiology of the disease, which also includes wind-driven mite transmission. Movement of virus from infected volunteer plants to new wheat by mites is considered a significant part of the overall disease cycle. Avoidance and removal of volunteer plants is an important part of disease management. Insecticides and miticides have not been effective in US studies.

This report documents the further expansion of the range of this virus to Western Australia. This is not an especially surprising announcement as the Minister for Agriculture Kim Chance notes in the comments above. It is quite likely that the virus has been there for some time in crop or other wild grass hosts.

Map: Western Australia, Esperance
<http://www.ga.gov.au/education/facts/mapproj/sw.htm>

Pictures:
Disease cycle:
<http://ianrpubs.unl.edu/plantdisease/graphics/ec1871-6.gif>
Leaf symptoms:
<http://www2.dpi.qld.gov.au/images/8658.jpg>
Wheat curl mite vector
<http://www.plantmanagementnetwork.org/pub/php/research/2004/wheat/image/volunteer1sm.jpg>

Links:
<http://www.grdc.com.au/growers/as/wsmv.htm>
<http://www.abc.net.au/landline/stories/s899307.htm>
<http://www2.dpi.qld.gov.au/health/12407.html>
<http://www.grdc.com.au/growers/res_upd/south/s06/edwards.htm>
<http://www.uky.edu/Ag/Entomology/entfacts/fldcrops/ef117.htm>
<http://www.ext.nodak.edu/extpubs/plantsci/smgrains/pp646w.htm>
<http://www.oznet.k-state.edu/path-ext/factSheets/Wheat/Wheat%20Streak%20Mosaic%20Virus.asp>
<http://www.ictvdb.rothamsted.ac.uk/ICTVdB/57020006.htm>
- Mod.JAD]

[see also in the archive:
2005
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Wheat streak mosaic - Australia (NSW) 20051029.3159
2004
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Wheat streak mosaic virus - Argentina: 1st report 20040922.2614
2003
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Wheat streak mosaic - Australia (12) 20030603.1354 Wheat streak mosaic, first report - Australia (Canberra) 20030417.0941]