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EARLY BLIGHT AND DICKEYA, POTATO - UK: UPDATE
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[1] Early blight: alert
[2] _Dickeya solani_ quarantine - Scotland
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[1] Early blight: alert
Date: Mon 1 Feb 2010
Source: Farmers Weekly [edited]
<http://www.fwi.co.uk/Articles/2010/02/01/119777/UK-potato-production-39increases-alternaria-threat39.htm>
UK potato production 'increases alternaria threat'
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Trends in UK potato production appear likely to increase the risk of
early blight, becoming a serious problem in the UK, SAC's [Scottish
Agricultural College] Ruairidh Bain said. The factors that have
increased alternaria in continental Europe in the past 10 years are
all trends happening in the UK, he said. Those included changes to
more susceptible varieties, warmer periods in the growing season,
more crops being irrigated (alternaria likes alternating wet and
dry), reduced nitrogen, and changes in fungicide use.
Control relied on fungicides and varietal resistance mainly, he said.
A list of 15 varieties with recorded alternaria infections in the
past 2 seasons had been produced. The strongest fungicides currently
appeared to be the strobilurins. "Unfortunately there is potential
for resistance to the strobilurins. In USA there was insensitivity
within 2 years," he said
[Byline: Mike Abram]
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Communicated by:
ProMED-mail
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[2] _Dickeya solani_ quarantine - Scotland
Date: Mon 1 Feb 2010
Source: Farmers Weekly [edited]
<http://www.fwi.co.uk/Articles/2010/02/01/119774/Dickeya-infected-potato-seed-may-not-be-replanted-in.htm>
Dickeya-infected potato seed may not be replanted in Scotland
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Seed crops infected with _Dickeya solani_, a new more aggressive form
of blackleg, could be taken out of seed production in Scotland, Gerry
Sadler of SASA [Science and Advice for Scottish Agriculture agency]
told growers. The proposal to have a zero tolerance to the bacterial
pathogen was part of a Scottish government consultation, he explained.
"It would mean amendments to the Seed Classification and Plant Health
schemes," he said. Crops infected with _Dickeya_ in Scotland would
not be allowed to be replanted for either seed multiplication or
ware. "You would have to sell your crop for immediate processing or
packing. It is quite a draconian measure." For crops sold off farm,
hygiene would be crucial, he added.
_Dickeya solani_ was now responsible for the majority of blackleg
cases in the Netherlands causing an estimated 30 million Euros [USD
41 million] in annual losses, he said. In Scotland, it had been found
in 2 crops of ware grown from English-grown seed [tubers] of Dutch
origin, and also in variety trial material, while in England around
10 cases had been confirmed in 2009 in seed and ware crops.
"We need to keep it out. As well as the threat to our own production,
Scotland is one of the few areas free from it, so it also gives us a
competitive advantage," he said. Part of the threat is that it causes
symptoms even at very low levels of inoculum, and is very aggressive
causing tubers to rot before harvest in some cases.
A nil tolerance approach is unlikely for England and Wales. "The
situation is very different as there is a vast amount of Dutch seed
brought in by English growers, which would make it difficult to
introduce a nil tolerance, so they are likely to rely on existing
blackleg measures."
[Byline: Mike Abram]
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Communicated by:
ProMED-mail
<promed@promedmail.org>
[Early blight
-------------
Early blight of potato and tomato is caused by the fungus _Alternaria
solani_. It causes leaf spots and tuber blight on potato, and leaf
spots, fruit rot, and stem lesions on tomato. The disease can occur
over a wide range of climatic conditions and can result in complete
defoliation and severe yield losses. The pathogen often causes no
visible symptoms until plants approach maturity. It is spread with
infected plant material (including tubers, transplants and seed), by
mechanical means, wind, and rain. Solanaceous weeds and volunteer
crop plants may serve as pathogen reservoirs. Disease management
includes use of certified clean propagation material, fungicides,
crop rotation, and use of cultivars with reduced susceptibility.
Strobilurins are strongly antifungal agents produced by fungi.
Pathogens must be expected to develop resistance or tolerance over
time, and many strains of _A. solani_ with increased tolerance levels
have emerged (for example, see ProMED-mail post 20090325.1163). This
is of major concern to potato and tomato industries worldwide.
Blackleg
--------
Blackleg caused by _Pectobacterium carotovorum_ subsp. _atrosepticum_
can cause severe losses in potato crops. However, an even more
virulent form of blackleg emerged in recent years as a major threat
spreading in Europe and Israel. The cause has only been identified as
a new bacterial species in 2009 (ProMED-mail post 20091207.4162). The
new pathogen is currently referred to as _Dickeya solani_. Symptoms
resemble "traditional" blackleg and include wilting of plants and
tuber rot, but the disease appears to be more aggressive and causes
damage under a wider range of conditions and at lower bacterial
loadings. Preliminary results from Europe indicate that the new
species will rapidly take over as the principal cause of
blackleg-like symptoms in potato crops.
The bacterium is spread with contaminated plant or other material
(including seed tubers), by mechanical means, and water. Disease
management includes seed tuber handling and cultural techniques, use
of clean planting material, and phytosanitation to prevent
introduction of the pathogen from external sources. Low levels of
seed tuber infection pose a major risk of pathogen spread, and
therefore quarantine measures and certification schemes as described
in item 2 are a vital part of disease management.
Maps of the UK:
<http://www.lib.utexas.edu/maps/europe/united_kingdom.gif> and
<http://healthmap.org/r/008E>
Pictures
Early blight lesions on potato leaf:
<http://www.ag.ndsu.edu/pubs/plantsci/hortcrop/pp1084-4.gif>
Early blight affected potato tubers:
<http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/images/plantpath/colorslide/pottubr-earlyblt-cjb.jpg>
Blackleg of potato, crown and stem symptoms:
<http://www.blackthornarable.co.uk/photography/potatoes/disease/T048-0012.jpg>,
<http://ipmnet.org/plant-disease/plant_images/Potato_Black_Leg_Stem_A.jpg> and
<http://www.blackthornarable.co.uk/photography/potatoes/disease/06-28-01-S2%20%2009%20POTATOES%20BLACKLEG_jpg.jpg>
Blackleg affected potato tuber:
<http://www.blackthornarable.co.uk/photography/potatoes/disease/t157-06%20potato%20tuber%20blackleg_jpg.jpg>
and
<http://people.umass.edu/psoil120/images/blackleg.jpg>
Links
Early blight fact sheets (with pictures):
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Potato_EarlyBlt.htm>,
<http://www.aces.edu/pubs/docs/A/ANR-1052/ANR-1052.pdf>, and
<http://ohioline.osu.edu/hyg-fact/3000/3101.html>
Management of potato diseases including early blight:
<http://archives.eppo.org/EPPOStandards/PP2_GPP/pp2-02-e.doc>
_A. solani_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=444460>
Information on strobilurins:
<http://www.answers.com/topic/strobilurin>,
<http://grounds-mag.com/mag/grounds_maintenance_strobilurin_fungicides_natures/index.html>,
and
<http://www.ibwf.de/ibwf_his&act_en.htm>
Information on _D. solani_:
<http://www.thefera.com/plants/plantClinic/documents/plantClinicNews/august09Issue.pdf>
Information on potato blackleg:
<http://www.ipm.ucdavis.edu/PMG/r607100111.html>,
<http://www.apsnet.org/Education/LessonsPlantPath/BlacklegPotato/default.htm>,
<http://ipmnet.org/plant-disease/disease.cfm?RecordID=882>, and
<http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2003/20hrt03a7.htm>
(with pictures)
Genus _Dickeya_ taxonomy:
<http://www.uniprot.org/taxonomy/204037> and
<http://www.bacterio.cict.fr/d/dickeya.html>
SAC:
<http://www.sac.ac.uk/>
SASA:
<http://www.sasa.gov.uk/>. - Mod.DHA]
[see also:
2009
----
Dickeya solani blackleg, potato: new pathogen 20091207.4162
Potato diseases - UK, USA 20090821.2960
Multiple pathogens, tomato, capsicum, strawberry - India 20090622.2284
Early blight, potato - Canada: new strains 20090325.1163
Blight & undiagnosed disease, potato, chilli - Bhutan 20090211.0612
Leaf blight, potato - Bangladesh: (KH) 20090121.0255
2008
----
Soft rot, potato - UK: origin 20081112.3567
Fungal diseases, potato - Bangladesh 20080107.0091]
...................................dha/mj/mpp
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