A ProMED-mail post
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ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>

[1] Saskatchewan: clubroot alert
[2] Spread of clubroot on farm equipment

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[1] Saskatchewan: clubroot alert
Date: Thu 8 May 2008
Source: Stormwire [edited]
<http://storm-wire.blogspot.com/2008/05/bottom-line-weather-points-agriculture_6343.html>

Crop disease warning goes out to Saskatchewan canola farmers

Canola farmers in Saskatchewan have been told to be on high alert against a crop disease called clubroot. More than 60 canola fields were infected last year [2007] in the neighboring province of Alberta, which experienced severely reduced canola yields.

The Saskatchewan agriculture ministry described clubroot as "harmful and swift-moving." Clubroot has not been detected in Saskatchewan, but farmers have been told that it is "extremely important" for producers to prevent the crop disease before it becomes entrenched and begins to spread. Saskatchewan growers are expected to seed up to
7.5 million acres (about 3 million ha) of canola this year [2008], and the province anticipates a record crop, according to the Eastern Edition of Country Guide.

Clubroot, a soil-borne disease, affects the roots of cruciferous vegetables and crops such as cabbage, cauliflower, broccoli, brussels sprouts, turnip, rutabaga, radish, canola, and mustard. Cruciferous weeds such as stinkweed, shepherd's-purse, and wild mustard can also host the disease. Clubroot is mainly spread by soil movement containing soil-borne spores. Soil transport can occur by wind or water erosion, in manure from animals fed contaminated feed, and by earth tag on seed or on field machinery, the province said.

Dr Ron Howard, research and extension specialist with the Crop Diversification Centre in Brooks, Alberta advises producers to scout fields regularly for clubroot. Producers should also prevent the introduction of the pathogen into fields by thoroughly cleaning their farm equipment.

[Byline: John Adams]

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[2] Spread of clubroot on farm equipment
Date: Thu 8 May 2008
Source: The Western Producer [edited]
<http://www.producer.com/free/editorial/news.php?iss=2008-05-08&sec=news&sto=001>

Clubroot hitchhikes from field to field

Bob Wasieczko got more than he paid for at a recent auction sale. He believes the air seeder he bought likely has spores from clubroot, a serious canola disease.

The Thorsby, Alberta, farmer bought the air seeder from an auction near Leduc and he knows the farmer had clubroot on at least 5 quarters of land, but he didn't think about that until after he bought the machine.

[Byline: Mary MacArthur]

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[Clubroot of _Brassicaceae_ is caused by the fungus _Plasmodiophora brassicae_. It is a destructive soil-borne disease which affects nearly all cultivated, as well as many wild and weed members of this family. A number of non-brassicaceous hosts are also known, but clubbing of roots does not occur on these. The pathogen is found worldwide and is most damaging in temperate regions and tropical highlands. It enters root hairs and wounded roots and multiplies rapidly, causing abnormal enlargement of the underground stem, taproot, or secondary roots. These roots often decay before the crop has matured, releasing many resting spores, which can survive for a decade in the absence of a susceptible host plant. Affected plants are stunted and may have discoloured purple leaves. Due to the distortion of the root, plants may wilt in dry weather and then recover at night.

The fungus has a complex disease cycle and is spread with contaminated soil, plant material, water, and by human activities.
Disease management is difficult due to the longevity of the spores and the inaccessibility of underground plant parts to fungicides.
Raising soil pH by addition of lime has been shown to be effective but the reasons are unknown and it is hardly practicable on large fields. Use of clean planting material is essential. The pathogen includes numerous pathotypes which have hampered efforts to breed cultivars with durable resistance.

In Canada, clubroot on canola was detected for the 1st time in Alberta in 2003 where it has been spreading since (see recent ProMED-mail post no. 20080407.1272). At least 2 prevalent pathotypes have been reported in Alberta to date, and a new more virulent strain of the pathogen appears to have emerged recently. There is a real risk of these fungal races spreading to neighbouring provinces, as illustrated by item [2] above. Although different strains are reported to affect different hosts to varying degrees, the possibility of local spread between different susceptible brassica crops may need further investigation.

Maps of Canada:
<http://www.lib.utexas.edu/maps/americas/canada_pol_1986.gif> and <http://healthmap.org/promed?v=55.4,-101.9,4>

Pictures
Clubroot symptoms on canola roots:
<http://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/ba3468a2a8681f69872569d60073fde1/
83d8f3ce22f85e8487256e9f006f0d09/Information/6.1DE!OpenElement&FieldElemFormat=jpg>
Cabbage with clubroot:
<http://vegetablemdonline.ppath.cornell.edu/PhotoPages/Crucifers/Clubroot/CruciferClubFS2.htm>
Cabbage field with clubroot symptoms:
<http://vegetablemdonline.ppath.cornell.edu/Images/Crucifers/Clubroot/Clbrt_Crucfs1.jpg>

Links
Additional news story:
<http://7thspace.com/headlines/280377/_disease_poses_risk_to_provincial_canola_crop.html>
Information on clubroot of canola:
<http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex8593?opendocument>,
<http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/faq7389?opendocument>
and
<http://webpub2.strathcona.ab.ca/Strathcona/Rural+Life/Country+Talk/March+2006/Clubroot+disease+of+canola.htm>
Information on clubroot on crucifer crops:
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Crucifers_Clubroot.htm>
Disease cycle of _P. brassicae_:
<http://vegetablemdonline.ppath.cornell.edu/PhotoPages/Crucifers/Clubroot/CruciferClubFS3.htm>
_P. brassicae_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=214750>. 
- Mod.DHA]

[see also in the archive:
Fungal diseases, oilseed rape - UK, Canada 20080407.1272 Brassica diseases - Turkey, Nepal 20080213.0572
2007
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Clubroot, canola - Canada (AB) 20070927.3199
2005
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Clubroot, canola - Canada (AB) (02) 20051113.3319 Clubroot, canola - Canada (Alberta) 20050512.1301]