A ProMED-mail post
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In this report:
[1] 1st report, Australia
[2] Control
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[1] 1st report, Australia
Date: April 2012
Source: Plant Disease [edited]
[Ref: R Khangura & D Wright: First report of club root caused by _Plasmodiophora brassicae_ Woronin on canola in Australia. Plant Disease (2012) 96; DOI: 10.1094/PDIS-11-11-1006-PDN]
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In 2009, a disease survey was conducted in 97 commercial canola fields in Western Australia (WA) by the Department of Agriculture and Food, Western Australia (DAFWA). In about 20 percent of the fields from the northern agricultural region of WA, small patches were observed where canola plants were showing symptoms of stunting and wilting. Small galls and club like structures were observed on their roots. Cortical cells were enlarged and full of resting spores, and plasmodia and zoosporangia were also observed.
The identity of _Plasmodiophora brassicae_ was confirmed by PCR. [The results] indicate that the _P. brassicae_ pathotype from WA may be different from the one found in Alberta, Canada. However, pathotypes from vegetable brassicas from Australia have been found similar to the populations present in the US.
Pathogenicity was tested. Five weeks after inoculations, small galls were observed on the roots of 3 inoculated plants, and the control plants remained symptomless. Resting spores were recovered from the galls. Presence of _P. brassicae_ in the affected roots was further confirmed by PCR. To our knowledge, this is the 1st report of club root of canola in Australia.
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[2] Control
Date: Thu 3 May 2012
We did successful trials and registration of the Mitsui fungicide flusulfamide for the control of clubroot of brassicas. A suspension concentrate of non-systemic bacteriocide and fungicide [was used] for the control of clubroot disease in _Cruciferae_ (cabbages) (Active
ingredient: Flusulfamide (benzenesulfonanilide) 220 g/l).
Economically, the key was to treat the planting hole or the seed row (for canola) rather than trying to dose the entire field, which was far too expensive to be viable.
The fungicide is a fumigant and creates a zone around the roots of the cabbage or canola in which roots can grow without becoming infected.
Outside the zone, they do get infected, but [the plants] have enough roots to grow a full crop.
The research lead to the product being registered in South Africa, where flusulfamide is also registered for control of potato scab.
However, we failed to publish it, so it would be good to share the information in this way.
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Professor Mark Laing
School of Agricultural Sciences and Agribusiness University of KwaZulu-Natal Scottsville, Pietermaritzburg 3209 South Africa <laing@ukzn.ac.za>
[Clubroot of _Brassicaceae_ is caused by the fungus _Plasmodiophora brassicae_. It is a destructive soilborne disease affecting nearly all cultivated members of the family, including oilseed rape (_Brassica napus_; "canola" refers to a group of specific varieties), cabbages and turnip, as well as many wild species which may serve as pathogen reservoirs. It is found worldwide and is most damaging in temperate regions and tropical highlands.
The fungus enters root hairs and wounded roots. It multiplies rapidly causing abnormal enlargement of the underground stem, taproot or secondary roots ("clubs"). Affected roots often decay before the crop has matured. Depending on the timing of infection in the crop cycle, symptoms may include wilting, stunting, and yellowing of plants, or premature ripening resulting in shriveled seeds. Due to the distortion of the roots, plants may wilt in dry weather and then recover at night.
The pathogen is composed of numerous pathotypes, which makes breeding crop cultivars with durable resistance difficult. Several of the pathotypes are known to occur in Alberta, Canada (see link below), and it is not clear which one is referred to in item [1] above.
Decaying roots release many resting spores which can survive in the soil for a decade or more in the absence of a susceptible host plant.
The disease can be spread with soil (for example on agricultural machinery), farming activities and infected plant debris. Use of clean planting material and phytosanitary measures to prevent spread between fields is essential.
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 is hardly practicable on large fields. We are, therefore, most grateful to Prof. Laing for sharing the very useful information in item [2] above.
Maps
Australia:
Western Australia:
Pictures
Clubroot symptoms on roots of oilseed rape:
and
Clubroot affected oilseed rape plants:
(affected field)
Clubroot symptoms on cabbage:
and
(affected field)
Links
Information on clubroot of oilseed rape:
and
Multiple clubroot pathotypes in Alberta:
Information on clubroot on crucifer crops:
Disease cycle of _P. brassicae_:
_P. brassicae_ taxonomy:
- Mod.DHA]
[see also:
Clubroot, oilseed rape - Canada: (MB) 20120502.0994
2011
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Clubroot, oilseed rape - Canada: (SK) 20111007.3012
2010
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Clubroot, oilseed rape - Canada: (AB), spread 20100118.0206
2008
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Clubroot, canola - Canada (02): (AB) 20080916.2899 Clubroot, canola - Canada (SK): alert 20080509.1586 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]
Topics
Species
