A ProMED-mail post <http://www.promedmail.org>
ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>
Date: Wed 24 Jul 2019
Source: No-Till Farmer [edited]
<https://www.no-tillfarmer.com/articles/8982-cercospora-leaf-spot-spotted-in-nebraska-panhandle-sugarbeet>
Cercospora leaf spot (CLS) has long been problematic to sugar beet production throughout the eastern and Great Lakes production areas of the United States. In western Nebraska, it has been sporadic. However, when it does occur, it can be very destructive.
The symptoms characteristic of this disease were observed on the lower leaves of sugar beets at the [University of Nebraska] Panhandle Research and Extension Center. This suggests that infection occurred before the 4th of July [2019] which is incredibly early for this in western Nebraska. Many of the new leaves may already be infected, but not exhibiting symptoms yet. Infection of the upper leaves is where the economic loss occurs in both tonnage and sugar content.
It is definitely time to begin scouting fields closely. Fungicide applications may be necessary if it continues to rain and stay warmer at nights. This is a devastating disease if it becomes established and is difficult if not impossible to properly manage. You can never play catch-up with this disease.
[Byline: Bob Harveson]
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Communicated by: ProMED-mail <promed@promedmail.org>
[Leaf spot caused by _Cercospora beticola_ is considered the most destructive foliar diseases of sugar beet and related crops. It affects most species of _Beta_ (cultivated and wild) and also many weed species in the Amarantaceae and Chenopodiaceae families that can serve as pathogen reservoirs. Symptoms on sugar beet (_Beta vulgaris_) include circular leaf spots with characteristic black centres that can coalesce into necrotic areas and, in severe cases, lead to complete leaf collapse. During severe outbreaks, new leaf growth can be seen emerging from the centre of collapsed leaves. The disease reduces photosynthetic ability and vigour of the plant and, therefore, yield and quality of beet crops. Disease development is favoured by high humidity and warm temperatures.
The fungus is spread mainly with infected plant material or contaminated seeds and can survive on infected crop residues for up to 2 years. Disease management usually requires an integrated approach, including phytosanitary methods, cultural practices and fungicides.
Fungicide resistant strains are emerging, for example, strobilurin resistant strains in the UK and the USA (ProMED-mail posts http://promedmail.org/post/20170413.4967611,
http://promedmail.org/post/20120216.1043062]. Rotating or mixing chemical classes of fungicides is used to extend the useful life of individual compounds. Partial genetic resistance to the pathogen in some _Beta_ varieties is used in breeding programmes to develop new crop cultivars.
Leaf spot diseases on a range of crops (such as peanut, soybean, coffee, maize) can be caused by other fungi previously classified as _Cercospora_ species. While some of them have since been attributed to different genera, the diseases are often still referred to as cercospora leaf or eye spots.
Maps
USA:
<http://www.mapsofworld.com/usa/usa-state-and-capital-map.html> and <http://healthmap.org/promed/p/229>
Individual states via:
<http://www.mapsofworld.com/usa/states/>
Pictures
Cercospora symptoms on beet leaves:
<https://c1.staticflickr.com/9/8606/15636366963_d0b6a16854_b.jpg>,
<https://pnwhandbooks.org/sites/pnwhandbooks/files/plant/images/sugar-beet-beta-vulgaris-cercospora-leaf-spot/sugarbeetcercosporaleafspot.jpg>,
and
<https://www.ars.usda.gov/images/docs/10537_10731/cercospora1.jpg>
Cercospora leaf spot, symptoms on whole beet plant:
<https://www.ag.ndsu.edu/cpr/images/07-24-13/khan.figure_2.damage_to_older_leaves.lesions.png/>
and
<https://www.ag.ndsu.edu/publications/crops/comparison-of-cercospora-and-bacterial-leaf-spots-on-sugar-beet/150-cercospora-leaves-opt.jpeg>
Comparison of cercospora with other beet leaf spots:
<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://3.bp.blogspot.com/-MhsLC1MM7Mw/VdXTkuSJZnI/AAAAAAAAAbk/NXeCA3TfWzI/s1600/sugarbeet-cercospora-check.jpg>
Links
Cercospora leaf spot information:
<http://extensionpublications.unl.edu/assets/pdf/g1753.pdf>,
<http://www.ipm.ucdavis.edu/PMG/r735100511.html>,
<https://cropscience.bayer.co.uk/threats/diseases/sugar-beet-diseases/cercospora-leaf-spot-beet/>,
<http://cropwatch.unl.edu/plantdisease/sugarbeet/cercospora-leaf-spot>,
and
<https://www.researchgate.net/publication/227336862_Cercospora_Leaf_Spot_Disease_of_Sugar_Beet>
Effect of CLS on different sugar beet varieties, resistance breeding &
control:
<https://www.frontiersin.org/articles/10.3389/fpls.2018.00222/full>,
<https://juser.fz-juelich.de/record/188143/files/FZJ-2015-01604.pdf>,
and
<http://www.wolf-pflanzenklinik.de/The_IPM_Sugar_Beet_Model.pdf>
_C. beticola_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=162050>
Cercospora diseases on other crops:
<http://www.oisat.org/pests/diseases/fungal/cercospora_leaf_spot.html>
Species and taxonomy of genus _Beta_:
<http://www.plantnames.unimelb.edu.au/Sorting/Beta.html>
- Mod.DHA]
[See Also:
2018
----
Cercospora leaf spot, sugar beet - France
http://promedmail.org/post/20181015.6091129
2017
----
Cercospora leaf spot, sugar beet - UK: strobilurin resistance
http://promedmail.org/post/20170413.4967611
2012
----
Cercospora leaf spot, sugarbeet - USA: (MI,ND) new strains
http://promedmail.org/post/20120216.1043062
2010
----
Cercospora leaf spot, sugarbeet - UK: alert
http://promedmail.org/post/20100709.2297
2007
----
Cercospora & powdery mildew, sugar beet - UK
http://promedmail.org/post/20070801.2478
and additional items on cercospora diseases in the archives]
Topics
Species
