A ProMED-mail post <http://www.promedmail.org>
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Date: Tue 4 Apr 2017 17:03 BST
Source: Farmers Weekly [edited]
<https://www.fwi.co.uk/arable/fungicide-resistant-cercospora-found-uk-sugar-beet.htm>

Resistance to one of the key fungicide groups used to control cercospora leaf spot in sugar beet has been discovered in the UK for the 1st time. Samples from Cornwall, Suffolk, and Lincolnshire, collected as part of a large-scale European monitoring programme, have confirmed disease resistance to all strobilurin fungicide chemistry.

The British Beet Research Organisation's (BBRO) Mark Stevens says the discovery is concerning, but that it needs to be viewed in context.

While cercospora can be a serious disease and is widespread across Europe, it is not the principal disease threat to crop performance in the UK. He says that further work is needed to determine the scale and significance of the resistance.

[Byline: Oliver Hill]

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Communicated by:ProMED-mail <promed@promedmail.org>

[Leaf spot caused by _Cercospora beticola_ is the most destructive foliar diseases of beet crops in warm and humid growing areas. It affects most species of _Beta_ (cultivated and wild) and also many weed species in the Amaranthaceae and Chenopodiaceae families which can serve as pathogen reservoirs. Symptoms on sugar beet (_Beta vulgaris_) include circular leaf spots with characteristic black centres that coalesce and, in severe cases, can lead to complete leaf collapse. During severe outbreaks, new leaf growth can be seen emerging from the centre of collapsed leaves. The disease reduces yield and quality of beet crops. Disease management generally relies on fungicides, but resistant _C. beticola_ strains are emerging.

Partial genetic resistance to the pathogen in some _Beta_ varieties is used in breeding programmes to develop new crop cultivars.

Strobilurins are strongly antifungal agents produced by fungi. Being derived from natural products, they are considered environmentally safe. Like several other fungicide classes, they have single-site activity and therefore pathogens must be expected to develop resistance or tolerance over time. Since they are used against most major fungal crop diseases, pathogen resistance is of major concern to many primary industries worldwide. Rotating or mixing chemical classes of fungicides is used to extend the useful life of the compounds.

Maps

UK:

<http://www.lib.utexas.edu/maps/europe/united_kingdom.gif> and <http://healthmap.org/promed/p/40>

UK counties and regions:

<http://www.picturesofengland.com/images/mapofengland/england-counties.gif>

and

<http://www.picturesofengland.com/mapofengland/regions.html>

Pictures

Cercospora symptoms on beet leaves:

<https://c1.staticflickr.com/9/8606/15636366963_d0b6a16854_b.jpg>,

<http://goo.gl/m0vpSx>, and

<https://www.ars.usda.gov/images/docs/10537_10731/cercospora1.jpg>

Cercospora leaf spot, symptoms on whole beet plant:

<http://goo.gl/NeRFev>, and

<http://goo.gl/U159QM>

Comparison of cercospora with other leaf spot diseases:

<http://extensionpublications.unl.edu/assets/html/g1753/build/graphics/g1753-2.jpg>

Cercospora affected beet fields:

<https://www.ag.ndsu.edu/cpr/images/09-15-16/ppth-1-2.png> and <http://goo.gl/e21MIe>

Links

Additional news stories:

<https://www.farminguk.com/News/First-cases-of-fungicide-resistant-Cercospora-found-in-UK-sugar-beet_46086.html>

and

<http://www.eadt.co.uk/news/sugar_beet_fungal_disease_cercospora_beticola_found_in_suffolk_one_of_first_cases_confirmed_in_uk_1_4961771>

Cercospora leaf spot information:

<http://www.bspp.org.uk/publications/molecular-plant-pathology/pathprofiles/pathprofile38.htm>,

<http://www.ipm.ucdavis.edu/PMG/r735100511.html>,

<http://cropwatch.unl.edu/plantdisease/sugarbeet/cercospora-leaf-spot>

and

<http://www.sbreb.org/brochures/cercospora/leafspot.htm>

_C. beticola_ taxonomy:

<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=162050>

Information on strobilurins:

<http://www.apsnet.org/edcenter/advanced/topics/Pages/StrobilurinFungicides.aspx>'

<https://www.ncbi.nlm.nih.gov/pubmed/17474024>, and <http://goo.gl/mFgFIE> Species and taxonomy of genus _Beta_:

<http://www.plantnames.unimelb.edu.au/Sorting/Beta.html>

British Beet Research Organisation:

<http://www.bbro.co.uk/>

- Mod.DHA]

[See Also:

2012

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Cercospora leaf spot, sugarbeet - USA: (MI,ND) new strains

http://promedmail.org/post/20120216.1043062

2010

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Cercospora leaf spot, sugarbeet - UK: alert

http://promedmail.org/post/20100709.2297

2007

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Cercospora & powdery mildew, sugar beet - UK http://promedmail.org/post/20070801.2478]