A ProMED-mail post

<http://www.promedmail.org>

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International Society for Infectious Diseases <http://www.isid.org>

Date: Fri 2 Oct 2009

Source: The Grower Magazine [edited]

<http://www.thegrower.org/viewarticle.php?id=682>

Leafy brassica greens: emergency fungicide registration for downy mildew

The Pest Management Regulatory Agency (PMRA) recently announced the approval of an emergency use registration for Rampart [trademark of Loveland Products, Inc.] fungicide (potassium salts of phosphorous

acid) for suppression of downy mildew on leafy brassica greens in Ontario because of a severe downy mildew outbreak combined with a low supply of registered fungicides in eastern North America. Crops include mustard greens, bok choy, pak choy, yow choy, gai choy, collards, kale, mizuna, mustard spinach, and rape greens.

Ontario leafy brassica producers have identified downy mildew as a top disease priority for several years. Although there are a few registered downy mildew fungicides, the supplies of the key fungicides were used up very quickly in 2009 due to widespread disease outbreaks on several major crops. Without access to Rampart fungicide, the Ontario leafy brassica crops industry faced the risk of very serious losses to downy mildew in 2009 and in fact the risk of serious losses remains critical.

The emergency use registration of Rampart fungicide will help in the interim to manage the current downy mildew outbreak; however management of downy mildew requires a comprehensive Integrated Pest Management (IPM) and resistance management program with access to all available tools and strategies. Fungicide should be used in an IPM program and in rotation with other management strategies to adequately manage resistance.

[Byline: Jim Chaput, OMAFRA (Ontario Ministry of Agriculture, Food and Rural Affairs)]

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ProMED-mail

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[Downy mildew of _Brassica_ species is caused by the fungus _Hyaloperonospora parasitica_ (previously _Peronospora parasitica_).

It affects a range of crops in the family of _Brassicaceae_, including all types of cabbages, turnips, radish and oilseed rape.

Infection and disease development are favoured by cool, wet weather.

The pathogen mainly attacks foliage leading to yellowing and premature leaf drop. It may also be responsible for substantial losses in seedling production.

Spores are produced on the underside of leaves overnight and dispersed by wind and rain splash. The fungus is known to survive on seed and on several species of cruciferous weeds, and also as oospores in plant debris in the soil from one crop to the next. For disease management, as mentioned above, an integrated approach is most effective, including cultural practices to reduce leaf wetness, use of clean seeds or seedlings, and fungicides.

Maps

Canada:

<http://www.lib.utexas.edu/maps/americas/canada_pol_1986.gif>

Ontario:

<http://atlas.nrcan.gc.ca/site/english/maps/reference/provincesterritories/
ontario/referencemap_image_view>

<http://healthmap.org/r/00HF>

Pictures

Downy mildew symptoms on _Brassica_ species:

<http://www.omafra.gov.on.ca/IPM/images/brassica/test-your-knowledge/
2q-downy-mildew-zoom.jpg>

(leaf),

<http://www.omafra.gov.on.ca/IPM/images/brassica/diseases/downy-bok_zoom.jpg>

(leaf), and

<http://3.bp.blogspot.com/_QgZSYSb-h34/R_L0-pP8RKI/AAAAAAAAAxw/n4Lrafs8go0/s320/Cabbage-DownyMildew+(3).JPG>

(seedling)

Close-up of 'downy' growth of unspecified downy mildew fungus:

<http://lh4.ggpht.com/_QgZSYSb-h34/SgsfbwYxVRI/AAAAAAAABjI/haD2A0_fOuA/s400/DownyMildew-SweetWoodruff%20(5).JPG>

and

<http://lh5.ggpht.com/_QgZSYSb-h34/Sgsfem-nsjI/AAAAAAAABjM/63-I-AZJsDA/s400/DownyMildew-SweetWoodruff%20(11).JPG>

Links

Information on downy mildew of brassica crops:

<http://www.omafra.gov.on.ca/IPM/english/brassicas/diseases-and-disorders/downy-mildew.html#advanced>,

<http://www.umassvegetable.org/soil_crop_pest_mgt/disease_mgt/
broccoli_downy_mildew.html>,

and

<http://www.dpi.vic.gov.au/dpi/nreninf.nsf/v/
F57D9716EA8FFF4ACA2574210002E5F8/$file/Downy_Mildew_of_Brassicas.pdf>

General information on downy mildew fungi (with pictures):

<http://www.infonet-biovision.org/default/ct/107/pests>

_H. parasitica_ taxonomy and synonyms:

<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=374990>

_H. parasitica_ host associations:

<http://www.bioimages.org.uk/html/t117878.htm>

Rampart product information:

<http://www.kellysolutions.com/NC/showproductinfo.asp?Product_Name=RAMPART+FUNGICIDE&EPA_Id=34704-924>

Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA):

<http://www.omafra.gov.on.ca/english/index.html>. - Mod.DHA]

Website: http://www.isid.org

Published: October 9, 2009