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Date: Wed 6 Jun 2018 14:32:11 BST
Source: Farming UK [edited]
<https://www.farminguk.com/new s/Early-appearance-of-late-bli ght-raises-concerns-for-UK-tom ato-growers_49477.html>

A recent outbreak of late blight in UK tomato crops is likely to be a
new strain, as symptoms have been seen early in the season on young
plants. Some existing plant protection controls are proving
ineffective due to the apparent aggressiveness of this strain.

The limited number of applications allowed for authorised protective
and curative products for the disease during the growing season is
also causing concern for growers, due to its early appearance.

AHDB [Agriculture and Horticulture Development Board] has responded
quickly to the outbreak and will be conducting a trial to identify new
potential options to control the strain.. Cathryn Lambourne, AHDB,
said: "We were alerted to the issue in young plants in late March
[2018], the disease was confirmed and the genotype identified at The
James Hutton Institute. We are working quickly to raise awareness of
the emerging problem."

Symptoms of the new strain include brown stem lesions that start just
above the graft union and spread along affected stems.
--
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[Late blight of tomato and potato is caused by the fungus-like
organism (oomycete) _Phytophthora infestans_ and can cause 100 per
cent crop loss. The pathogen can also affect some other solanaceous
crops. In tomato, it causes lesions and rotting of leaves, stems, and
fruits; in potato, it affects leaves as well as tubers. The disease is
favoured by cool, moist conditions. It can spread rapidly within a
crop and destroy it within a few days. Under favourable conditions,
epidemics in tomatoes may be even more rapid than in potatoes.

The pathogen is spread by plant material (including tomato
transplants, potato seed tubers, plant debris, and volunteer crop
plants), mechanical means (including human and insect activities),
wind, and water. Disease management requires an integrated approach
and may include removal of pathogen reservoirs, crop rotation,
preventive fungicide treatments of planting material, and fungicide
sprays of crops. Certified clean planting stock and management
strategies for fungicide resistance of the pathogen are considered
vital to control late blight outbreaks. Commercial crop cultivars vary
in susceptibility to late blight. Development of resistant cultivars
is being counteracted by the adaptability of the pathogen.

Late blight is considered an increasing problem worldwide.
Considerable variation in aggressiveness between different pathogen
strains has been observed, but more virulent strains with additional
fungicide resistances and increased yield losses are emerging
frequently. In Europe, regional differences in pathogen population
diversity no longer exist and increasingly virulent strains have been
reported to emerge, mainly on potato (see previous ProMED-mail posts
in the archives).

Maps
UK:
<http://healthmap.org/promed/p /40> and
<http://www.lib.utexas.edu/map s/europe/united_kingdom.gif> (with
counties)

Pictures
Late blight on tomato:
<http://ipm.illinois.edu/ifvn/ volume15/images/tomato_late_bl ight.jpg>
Late blight on potato:
<http://farm1.static.flickr.co m/81/281344513_74bbffe5fe.jpg> and
<http://cdn.phys.org/newman/gf x/news/2013/keepingpacew.jpg> (resistant
vs. susceptible cultivars)
Microscopy of PLB infected cells:
<http://micro.magnet.fsu.edu/o ptics/olympusmicd/galleries/br ightfield/images/potatoblight. jpg>

Links
Additional news stories:
<https://www.agriland.ie/farmi ng-news/early-bouts-of-late- blight-causing-concern-for- tomato-growers/>
and
<https://www.hortweek.com/new- aggressive-blight-strain-found -young-tomato-plants/fresh- produce/article/1478235>
(subscription required)
Information on late blight:
<http://vegetablemdonline.ppat h.cornell.edu/factsheets/Potat o_LateBlt.htm>,
<http://www.apsnet.org/edcente r/intropp/lessons/fungi/ Oomycetes/Pages/LateBlight. aspx>,
and
<http://www.scri.ac.uk/researc h/pp/pestanddisease/blightepid emiologyandpopulationbiology>
PLB disease cycle:
<http://bit.ly/2lnDBQg>
PLB epidemiology and strains in Europe:
<http://www.springerlink.com/c ontent/j6685260n621hph2/fullte xt.html>
_P. infestans_ taxonomy:
<http://www.indexfungorum.org/ Names/NamesRecord.asp?RecordID =232148>
EuroBlight:
<http://euroblight.net/>
Global Initiative on Late Blight:
<https://research.cip.cgiar.or g/confluence/display/GILBWEB/ Home>
James Hutton Institute:
<http://www.hutton.ac.uk/>
- Mod.DHA]

[See Also:
Late blight, potato - India: strain Blue 13
http://promedmail.org/post/201 80418.5755980
Late blight, potato - Bangladesh: (RP)
http://promedmail.org/post/201 80110.5550872
2017
----
Late blight & post harvest rot, potato - Ireland & UK (NI)
http://promedmail.org/post/201 71124.5462543
Late blight, potato - UK: strain Dark Green 37
http://promedmail.org/post/201 71029.5412307
Late blight, potato - Bhutan: (CK)
http://promedmail.org/post/201 70619.5114985
Late blight, potato - Bangladesh (02): (RP)
http://promedmail.org/post/201 70209.4825828
Late blight, potato - Bangladesh: (RS)
http://promedmail.org/post/201 70115.4767829
2016
----
Late blight, potato - Uganda: (South West)
http://promedmail.org/post/201 60602.4260691
Late blight & undiagnosed virus, potato - Bangladesh: (RP)
http://promedmail.org/post/201 60121.3953451
2015
----
Late blight, potato - Spain: strain Blue13 1st rept, new A1/A2 strains
http://promedmail.org/post/201 50317.3237610
Late blight, potato - Nepal: (DN)
http://promedmail.org/post/201 50128.3127014
2013
----
Late blight, potato: new strains threat
http://promedmail.org/post/201 30111.1492024
2012
----
Late blight, potato - UK: strain Green 33
http://promedmail.org/post/201 20202.1031230
2010
----
Late blight type A2, potato - Estonia: 1st report
http://promedmail.org/post/201 01129.4298
Late blight, potato - Ireland: strain Pink 6
http://promedmail.org/post/201 00604.1851
Dickeya, leaf blights, potato - UK, Ireland
http://promedmail.org/post/201 00528.1775
Late blight, potato - Ireland: strain Blue13
http://promedmail.org/post/201 00212.0505
and additional items on late blight in the archives]
................................ ...................sb/dha/mj/j h
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