Sydney NSW, Australia
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8 days ago
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DOWNY MILDEW, GRAPEVINE – AUSTRALIA: (VICTORIA, NEW SOUTH WALES)
ProMED
http://www.promedmail.org
ProMED-mail is a program of the
Source: Australian Broadcasting Corporation (ABC) News [summ. Mod.DHA, edited]
https://www.abc.net.au/news/2022-12-16/mildura-dried-fruit-down-mildew-farmers-crop-loss/101774902
Up to 60 percent of the dried vine fruit in the Sunraysia region (southwestern New South Wales/northwestern Victoria) could be lost to the worst downy mildew outbreak in decades, triggered by recent rain. About 9000 tonnes of crops could be lost to the infection. The region produces 98 percent of the country’s dried vine fruit exports.
Dried Fruits Australia said the vines look quite good, but there are no bunches of grapes, they have dried up and fallen off. Some growers may not even harvest their grapes this 2022 season. Wine grapes have also been devastated by downy mildew. One grower said he has lost 70 percent of his wine crop
[Byline: Peter Sanders, Kellie Hollingworth]
—
Communicated by:
ProMED
[Downy mildew on grapevine is caused by the fungus-like organism (oomycete) _Plasmopara viticola_. It causes lesions on leaves which later become covered with white downy growth and turn necrotic. It can also affect flowers and fruits. Disease development is favoured by temperatures of 15 to 20 deg C (59 to 68 deg F) and moist conditions. In years with warm, extended wet periods during bloom, fruit clusters may be partially or totally destroyed. The disease can cause severe crop losses and occurs irregularly in most grape growing regions worldwide.
Spores are spread within a crop mainly by splashing rain, wind, or mechanical means. The pathogen survives between crops on infected plant debris as oospores, which are formed inside the host tissues. It is an obligate parasite and cannot be cultured in vitro. Disease management relies mainly on preventative fungicide applications according to forecasting services. Systemic fungicides are also available. All commercial grape cultivars are susceptible.
Downy mildews include many species of oomycetes in several genera which cause similar symptoms in a range of hosts, including many crops. Individual species usually have a narrow host range affecting only one or a few different hosts.
Maps
Australia (with states):
https://www.nationsonline.org/maps/australia-political-map.jpg and
https://promedmail.org/promed-post?place=8707386,17141
Sunraysia region:
https://upload.wikimedia.org/wikipedia/commons/1/1d/Outline_map_of_the_Mallee_and_Sunraysia_regions.png
Pictures
Downy mildew on grapevine leaves & bunches:
https://www.canr.msu.edu/grapes/uploads/images/DMgrapes-2_9-18-18.jpg,
http://web2.mendelu.cz/af_291_projekty2/vseo/files/9/1784.jpg,
https://i.pinimg.com/originals/b6/9d/aa/b69daafeaa444558d055ac67d538f046.png (upper & lower leaf surface),
https://thumbs.dreamstime.com/b/downy-mildew-grape-infestation-plasmopara-viticola-photo-shows-berries-48172310.jpg,
https://www.agric.wa.gov.au/sites/gateway/files/downy%20in%20bunches%20(20).JPG, and via
http://grapepathology.blogspot.com/2009/06/downy-mildew-gallery.html (photo gallery)
Links
Information on downy mildew of grapevine (with pictures):
https://gd.eppo.int/taxon/PLASVI,
https://doi.org/10.1079/cabicompendium.41918,
http://nicolewarduk.blogspot.com/2013/07/downy-mildew-in-grape-secrets-to.html,
https://grapes.extension.org/downy-mildew-of-grapes/,
http://www.arec.vaes.vt.edu/alson-h-smith/grapes/pathology/extension/factsheets/downy-mildew-grapevines.pdf,
https://www.apsnet.org/edcenter/disandpath/oomycete/pdlessons/Pages/DownyMildewGrape.aspx,
https://www.agric.wa.gov.au/table-grapes/downy-mildew-grapevines, and
https://www.syngenta.com.au/news/vineyard/downy-mildew-prevention-safe-option
_P. viticola_ taxonomy and synonyms:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=208592
and
http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=208592
– Mod.DHA]
Australia
Grapes
Downy_mildew
Global Plant Protection News 
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