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Date: March 3, 2007
From: QLD Department of Primary Industries and Fisheries [edited] <http://www.dpi.qld.gov.au/cps/rde/xchg/dpi/hs.xsl/30_5203_ENA_HTML.htm>

Queensland's first confirmed occurrence of tobacco streak virus (TSV) in mungbean crops has been detected in the Emerald district.

Department of Primary Industries and Fisheries senior extension development officer Anne Shepherd said that TSV was identified last year [2006] as the cause of the mystery disease that devastated Central Queensland sunflower crops in 2004 and continued to impact on the few crops sown in the past 2 summer seasons.

Ms. Shepherd said a number of Emerald district agronomists had now reported mungbean disease symptoms in dryland and irrigated crops that were inconsistent with known mungbean fungal or viral disorders.

"Diseased mungbean plant samples were forwarded to the DPI&F virologist Murray Sharman early this week, who confirmed TSV infection," Ms. Shepherd said.

Suspicions were raised by Belinda Chase, an agronomist with the Emerald agricultural consultancy company, Graham Spackman and Associates, who suspected the TSV infection in a mungbean crop that was heavily infested with thrips insects.

Ms. Shepherd said this TSV infected crop was adjacent to pasture country with a prolific stand of flowering parthenium weed. DPI&F pathologists have confirmed that parthenium weed was a known host of TSV in Central Queensland, linking it to the sunflower disease caused by TSV.

"It is likely the main source of the virus is infected parthenium pollen, which is carried by thrips. This sucking insect then transmits the virus when feeding on the mungbean plant," Ms. Shepherd said.

"Crop areas closest to the pathenium infested pasture recorded 100 per cent infection, whereas the TSV presence decreased to around 5 per cent in the centre of the mungbean field.

"Our immediate research objectives are to establish how widespread the TSV disease is in mungbean crops in the district, confirm that the parthenium is carrying TSV and identify which thrips are responsible for transmitting the virus to crops."

TSV symptoms on the mungbean plants include fine dark necrotic lines on the leaves, yellowing on the leaves that become large necrotic
(dead) patches, necrosis running down the petioles and the stem and death of the plant's growing terminal.

Ms. Shepherd said that last season, TSV was also found to be present in the Central Highlands' chickpeas. Other crops with known TSV susceptibility were cotton, peanuts and soybeans.

"At this stage, we are asking growers to report unusual crop symptoms to their agronomist or contact Emerald DPI&F field crop extension officers.

"We would like growers to describe the disease symptoms, record the location of affected plants and note the impact on crop yields."

Ms. Shepherd said there were a number of potential TSV management measures that could be adopted by mungbean growers to reduce the thrips population and promote the development of an economically viable and productive crop.

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

[Tobacco streak ilarvirus affects a number of crops, including bean, sunflower, peanut, maize, soybean and a range of vegetable and ornamental species. It is probably distributed worldwide and spreading in North America and the Pacific region. It is transmitted by vector insects (_Frankliniella occidentalis_ and _Thrips_ spp.), possibly by allowing virus from the surface of infected pollen to enter through feeding wounds. TSV can also be transmitted by mechanical inoculation and grafting, by pollen to the pollinated plant, and it is seed-transmitted in some species to different extents; it is not transmitted by contact between plants.

The weed referred to as a possible reservoir species and potential source of infected pollen is _Parthenium hysterophorus_. It is native to Mexico and the USA and is considered to be one of the 10 worst weeds worldwide, causing huge problems to agriculture and adverse effects on humans and animals.

Pictures of symptoms on sunflower:
<http://www.dpi.qld.gov.au/images/PlantIndustries_HealthPestsDiseaseAndWeeds/Sunflower-TSV-SeedlingDeath-168_rdax_168x134.jpg>
<http://www.dpi.qld.gov.au/images/PlantIndustries_HealthPestsDiseaseAndWeeds/Sunflower-TSV-RottenPith-168_rdax_168x134.jpg>.

Links:
TSV description at
<http://image.fs.uidaho.edu/vide/descr811.htm>
TSV infection of sunflower
<http://www.dpi.qld.gov.au/.../ 26_4134_ENA_HTML.htm>
Information on parthenium weed at
<http://www.iprng.org/>,
<http://www.cbit.uq.edu.au/parthenium/parthenium.html>.
- Mod.DHA]

[see also in the archive:
2006
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Tobacco streak virus, sunflower - Australia: 1st report 20060731.2118
2005
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Tobacco streak virus, mung bean - India: 1st report 20051214.3595
2003
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Tobacco streak virus, cucumber - India: 1st report 20030918.2363
2001
----
Tobacco streak disease, peanut - India 20011118.2839
Tobacco streak virus, sunflower - India 20010830.2057]

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