A ProMED-mail post
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International Society for Infectious Diseases <http://www.isid.org>
Date: Wed 24 Apr 2013
Source: Daily Monitor [edited]
<http://www.monitor.co.ug/Magazines/Farming/Farmers-count-losses-over-black-rot-disease-in-cabbage/-/689860/1757020/-/isufmpz/-/index.html>
Farmers count losses over black rot disease in cabbage
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Vegetable farmers, especially those who grow cabbages in Kayunga and Mukono districts [Central Region] are counting losses after a disease, which has been identified as the black rot disease, hit these areas.
According to an agricultural expert, the disease, locally known as kisanja, produces dark brown discoloration in leaves and they start to decay. He says planting healthy seeds and crop rotation that excludes planting of crucifers can help control the disease.
One of the farmers who has lost his cabbages to the disease says he had planted 4 acres [1.6 ha] of the crop. Another farmer says his cabbages were infected while still in the nursery bed. "This disease is frustrating us because we had embarked on growing vegetables which are marketable but we have instead incurred losses."
[byline: Fred Muzaale]
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[Bacterial black rot caused by _Xanthomonas campestris_ pv.
_campestris_ is one of the most important diseases of brassica crops, including cabbages, turnips, and oilseed rape. The pathogen can also affect cruciferous weeds, which can serve as pathogen reservoirs. The disease affects primarily above ground parts of the plants at any stage of growth. It can cause serious losses in yield and quality, especially in tropical and subtropical regions. Disease development is favoured by high humidity and warm temperatures. Symptoms may vary according to host and environmental conditions and generally include characteristic V-shaped lesions, leaf chlorosis, darkening of vascular tissue, extensive wilting, and necrosis. Pre-existing fungal lesions may increase the susceptibility of crops to black rot by providing entry points for the bacteria.
The pathogen is seedborne and can also be spread by mechanical means (including insects), plant debris, water, and wind. Disease management includes clean planting material (seed or transplanted seedlings), cultural practices, removal of weed reservoirs, and copper sprays.
Some black rot resistant brassica cultivars are available.
There are several other pathovars of _X. campestris_ with varying host specificity which affect a range of crops causing, for example, one of the bacterial wilts of banana (pv. _musacearum_; see previous ProMED-mail posts in the archives) and several leaf spot diseases on other vegetables.
Maps
Uganda:
<http://unimaps.com/uganda/mainmap.gif> and <http://healthmap.org/r/1wa6> Uganda districts:
<http://en.wikipedia.org/wiki/Districts_of_Uganda>
Pictures
Black rot on cabbage:
<http://eorganic.info/sites/eorganic.info/files/u302/other%20cabbage.JPG>
and
<http://www.longislandhort.cornell.edu/vegpath/photos/images/cabbage_blackrotx1200.jpg>
Black rot on cauliflower:
<http://vegetablemdonline.ppath.cornell.edu/Images/Crucifers/BlackRot_Cruc/BR_CrucFS8.jpg>
Links
Information on black rot of brassica crops:
<http://ohioline.osu.edu/hyg-fact/3000/3125.html>
<http://www.extension.org/pages/29925/managing-black-rot-of-cabbage-and-other-crucifer-crops-in-organic-farming-systems>,
and
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Crucifers_BR.htm>
_X. c._ pv. _campestris_ taxonomy:
<http://www.uniprot.org/taxonomy/340> - Mod.DHA]
[see also:
2008
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Brassica diseases - Turkey, Nepal 20080213.0572
2007
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Foliar diseases, brassica crops - UK 20070913.3037]
Topics
Species
