.

Capital Press [edited]
<http://www.capitalpress.info/main.asp?SectionID=67&SubSectionID=616&ArticleID=32647&TM=76493.2>
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While yellow leaf curl is making headlines, there is another tomato-damaging disease of greater concern for the industry right now. It's called spotted wilt, a virus spread by an insect called a thrips which measures about an eighth- to a quarter-inch in length, said UC [University of California] Davis plant pathologist Robert Gilbertson. "This virus, in the last 2 years, has increased in its frequency in tomatoes, especially in Fresno, Merced, and Kings counties," said Gilbertson.

The virus causes plants to wilt and turn a bronze color, with the plant's veins turning black before tissue begins to die, Gilbertson said. Young plants will die from the virus, while fruits on older plants develop rings.

Ross Siragusa, president and chief executive officer of the California Tomato Growers Association, said spotted wilt has caused "considerable economic damage" for some farmers, with one grower losing 500 acres (202.3 hectares) of tomatoes within the last few years. Because it's already done damage, spotted wilt is a bigger concern than yellow leaf curl for state tomato growers, Siragusa said.

Gilbertson said the California Tomato Research Institute is working with UC Cooperative Extension to look at early detection and new tomato varieties to control spotted wilt. The disease can be managed, Gilbertson said, with a combination of early detection, a spray program and virus management. Gilbertson added that California's system of disease management has worked "very well," as researchers and farm advisors work closely together.

[byline: Elizabeth Larson]

--
communicated by:
J Allan Dodds
former ProMED-mail plant disease moderator
<dodds@ucr.edu>

[_Tomato spotted wilt virus_ (TSWV; genus _Tospovirus_, family _Bunyaviridae_) has one of the broadest host ranges among plant viruses and has had a serious impact on many crop species worldwide causing up to 100
per cent yield loss in some instances. Diseases attributed to TSWV were 1st reported in Australia about 1915. It is one of the few plant viruses with a host range that includes dicots and monocots. Weed species can serve as
pathogen reservoirs.

TSWV is transmitted by various species of thrips, including the western flower thrips (_Frankliniella occidentalis_), the onion thrips (_Thrips tabaci_), and the chilli thrips (_Scirtothrips dorsalis_). The virus needs to be acquired during the nymph stage by feeding on infected plants, which will retain the ability to transmit it for the remainder of their lives. The virus multiplies in the vector insects but cannot be passed on from infected females through the eggs. TSWV is not seed transmitted but transmission by mechanical means has been reported.

New tospoviruses are being found frequently. They represent the only genus in the family of _Bunyaviridae_ that infect plants. Natural resistance appears to be rare amongst their plant hosts, but they infect the insect vectors without causing any symptoms. Scientists are discussing the possibility that tospoviruses may have evolved from an insect virus that acquired additional genetic information via recombination, either from a plant or from another plant virus, enabling the new virus to infect plants. For more information on tospoviruses see the recent ProMED-mail post 20070524.1670.

Map of US states
<http://www.census.gov/geo/www/us_regdiv.pdf>
World distribution map of TSWV
<http://www.eppo.org/QUARANTINE/virus/Tomato_spotted_wilt_virus/TSWV00_map.htm> 

Pictures:
TSWV symptoms on whole tomato plants:
<http://www.hos.ufl.edu/vegetarian/03/April/Mayfield_Fig1.jpg> and
<http://www.ag.auburn.edu/aaes/organicveg/images/clip_image002_000.jpg>
TSWV symptoms on tomato fruit:
<http://www.coopext.colostate.edu/4dmg/images/tswv1.jpg> and
<http://www.ces.ncsu.edu/copubs/ag/fnv/veg/005/spottedwilt.gif>
Symptoms of TSWV on several vegetable species:
<http://vegetablemdonline.ppath.cornell.edu/PhotoPages/Tomatoes/Tom_SpWilt/Tom_SpWiltPhotoList.htm> 

Electron micrograph of TSWV particles:
<http://www.rothamsted.bbsrc.ac.uk/ppi/links/pplinks/virusems/b6.jpeg>
Western flower thrips:
<http://www.insectimages.org/browse/detail.cfm?imgnum=4387048> and
<http://www.cals.ncsu.edu/course/ent425/text18/thrips.jpg>

Links
TSWV taxonomy and description:
<http://image.fs.uidaho.edu/vide/descr837.htm>
TSWV information:
<http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/tomswv.htm>,
<http://www.ipm.ucdavis.edu/PMG/r783102211.html>,
<http://www.defra.gov.uk/planth/pestnote/tswv.htm> and
<http://www.apsnet.org/online/feature/tospovirus/>
TSWV fact sheet:
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Virus_SpottedWilt.htm>
Description of western flower thrips vector:
<http://www.ricecrc.org/Hort/ascu/insects/wft.htm>
Thrips information:
<http://www.cals.ncsu.edu/course/ent425/text18/plantvectors.html>.
- Mod.DHA]


[see also in the archive:
Groundnut ringspot tospovirus, peanut - Argentina (Cordoba): 1st report
20070524.1670
2005
---
Tomato viruses - Ecuador 20051125.3418
Tomato spotted wilt, Sw5 resistance gene - Italy 20050329.0914
2004
---
Tomato spotted wilt, Iris yellow spot, onion - USA (GA) 20041031.2938
Tomato spotted wilt, pepper - Spain 20040605.1519
2003
---
Tomato spotted wilt, tomato - USA (FL & GA) 20031009.2539
2002
---
Tomato spotted wilt, tomato - USA (MA): Correction 20020627.4618
Tomato spotted wilt, tomato - USA (Massachusetts) 20020626.4608
Tomato spotted wilt, tomato - USA (North Carolina) 20020622.4565
Tomato spotted wilt, tomato - (USA) Virginia 20020620.4545
2001
---
Tomato spotted wilt tospovirus, soybean - Iran 20011229.3130
Tomato spotted wilt, peanut - Iran 20011220.3069
Tomato spotted wilt disease, tomato - Kenya 20011109.2778
Tomato viruses - Tunisia 20010926.2349
2000
---
Tomato spotted wilt tospovirus, crops - USA (Georgia) 20000617.0989
Tomato spotted wilt tospovirus - Europe 20000302.0286
Tospoviruses - Argentina 20000213.0197
Tospovirus, zucchini, courgette & cucumber - Brazil 20000129.0145
1997
---
Potato viruses - Saudi Arabia 19970414.0796]

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