A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: Tue 8 Jul 2014
Source: ABC (Australian Broadcasting Corporation) Rural [edited] <http://www.abc.net.au/news/2014-07-08/nrn-virus-continues/5580902>
Future of virus-affected canola unknown
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South Australian farmers affected by beet western yellows [see comment below] say their crops are facing an uncertain future. It's estimated around 7000 hectares of canola [varieties of oilseed rape] in the state could be affected; the worst case ever seen in Australia.
The virus is being transmitted by green peach aphids, which have thrived in recent warm conditions. Farmers and agronomists say they still don't know how to deal with the virus. Farmers face huge yield losses. Tests have indicated a 90 percent infection rate in some crops. [Farmers say] "[the crop is] just struggling to even stay alive, let alone put on any yield. We've never dealt with this before."
Agronomists and scientists are just as baffled. The South Australian Research and Development Institute [SARDI] says tests have confirmed very high rates of infection particularly in the lower north. But scientists are still investigating why this virus has spread so far and whether it may start affecting pulse crops.
SARDI's Greg Baker says spraying crops now would be a waste of time, because the virus-transmitting aphids are inactive. But, as the weather heats up, farmers should still monitor for early signs of aphid activity and use that as alert for crops being at risk and requiring preventative sprays.
News of the virus is spreading overseas and influencing the global canola price. Australia is the world's 2nd largest producer of canola, with South Australia a major exporter to Europe.
[Byline: Lauren Waldhuter]
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[_Beet western yellows virus_ (BWYV; genus _Polerovirus_) affects over
150 species, including crops like beets, lettuce, sunflower, cabbage, bean, pea, chickpeas, tomato, capsicum and cucumber. Poleroviruses are largely confined to phloem tissue, resulting in yellowing symptoms, but may invade non-phloem tissue when co-infecting with, for example, potyviruses. European non-sugar beet infecting strains of BWYV have been reclassified as a separate species, _Turnip yellows virus_ (TuYV), in the genus. TuYV is considered an emerging threat to European oilseed rape production. Outbreaks have been reported, for example, in the UK, and the virus is also known to occur in Australia (ProMED-mail post 20100227.0653). Thus, the current outbreak in Australia may be due to this virus, rather than BWYV.
BWYV and TuYV cause progressive yellowing and loss of plant vigour in most of their hosts. Degree of damage depends upon virulence and persistence of the virus strain, as well as susceptibility of the crop variety.
Both viruses are transmitted by several aphid vectors (including green peach aphid, _Myzus persicae_) in a persistent manner and retained when the insects moult. They have no other means of spread. Disease management may be attempted by controlling vector insects (as suggested in the story above) and reducing the amount of available reservoir plants. Breeding programmes for TuYV resistant oilseed rape have been established in Europe (see link below).
Maps
Australia (with states):
<http://www.ga.gov.au/image_cache/GA4073.jpg>
South Australia:
<http://www.atn.com.au/sa/south/graphics/sth-map.jpg>
Pictures
TuYV/BWYV symptoms on oilseed rape leaf:
<http://c.photoshelter.com/img-get/I0000dKHMIynP2Kg/s> and <http://www.farmersguardian.com/pictures/610xAny/5/3/3/32533_TuYV_virus_symptoms.jpg>
BWYV symptoms on other hosts:
<http://vegetablemdonline.ppath.cornell.edu/Images/CropHosts/Escarole_Virus3.jpg>
(escarole endive) and
<http://ictvdb.bio-mirror.cn/WIntkey/Images/sy_bybwy.jpg> (sugar beet
field)
_M. persicae_ vector:
<http://www.entomology.umn.edu/cues/inter/inmine/inimage/greenpeach.jpg>
Links
Additional news story:
<http://www.abc.net.au/news/2014-07-01/nrn-canola-virus/5561790>
Information on TuYV in oilseed rape:
<http://www.oregin.info/stakeholders/meetings/shf07-Nov2009/Stevens_RRES_OREGIN_SHF7_Nov2009_TuYV.pdf>,
<http://archive.hgca.com/cms_publications.output/2/2/Publications/Final%20project%20reports/Turnip%20yellows%20virus%20%28syn%20Beet%20western%20yellows%20virus%29,%20an%20emerging%20threat%20to%20European%20oilseed%20rape%20production.mspx?fn=show&pubcon=4579>
and
<http://www.fwi.co.uk/articles/10/02/2014/143213/turnip-yellows-virus-resistant-osr-may-cut-losses.htm>
(resistance breeding)
BWYV disease information and description:
<http://www.ipm.ucdavis.edu/PMG/r441101411.html> (with host list) and <http://ictvdb.bio-mirror.cn/ICTVdB/00.039.0.02.003.htm>
Relationship between BWYV and TuYV:
<http://www.apsnet.org/publications/phytopathology/backissues/Documents/1972Articles/
Phyto62n11_1274.PDF>
Virus taxonomy via:
<http://ictvonline.org/virusTaxonomy.asp?version=2012>
Information on _M. persicae_:
<http://entnemdept.ifas.ufl.edu/creatures/veg/aphid/green_peach_aphid.htm>
and
<http://bayer.warinteractive.com/pestspotter_newc284.html?fn=details&con=2155&pestId=915>
SARDI:
<http://www.sardi.sa.gov.au>
- Mod.DHA]
[See Also:
2011
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Vegetable viruses - Australia: (WA, QL) 20110314.0817
2010
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Turnip yellows virus, oilseed rape - UK: (England) 20100227.0653
2008
----
Beet mosaic virus, lettuce - China: new host, (Shandong)
20080312.0990
2007
----
Beet and cucurbit viruses, multiple hosts - China: 1st reports 20070516.1564]
Topics
Species
