A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
[1] UK: spread of new strain
[2] Bangladesh: Rangpur, Rajshahi Division
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[1] UK: spread of new strain
Date: Sun 5 Apr 2009
Source: Farmers Weekly Interactive [edited]
<http://www.fwi.co.uk/Articles/2009/04/05/114942/new-blight-strain-demands-extra-vigilance.html>
New blight strain demands extra vigilance
With aggressive potato blight strain A2-Blue13 now dominant,
skill is again needed to strike the right balance between
effective control and acceptable fungicide use. The new strain
first showed up near Ipswich in 2005 and has rocketed in
prevalence from 38 percent that year to almost 80 percent now
leading to some of the worst potato blight on record. "We are
dealing with a different type of blight,"
advises Potato Council [PC] blight specialist Gary Collins. "It
is more aggressive, fitter and will come into crops earlier."
That A2-Blue13 is more damaging is not disputed. PC-funded
glasshouse trials show it is the most aggressive strain,
creating larger blight lesions and producing spores more rapidly
than other strains.
Significantly it can produce spores at less than 10 deg C (50
deg F) and the period between infection and sporulation is far
shorter -- typically 4.5 days for the new A2 blight, compared to
6 or 7 days for conventional blight.
SCRI [Scottish Crop Research Institute] Dave Cooke confirms the
rise of A2-Blue13. "The onward march of the Blue A2 blight
strain is really quite clear. Genotype testing of more than 1600
samples in
2008 has revealed it now represents 79 percent of the blight
population and is now dominant across the whole of Great
Britain."
So does that render Smith Periods obsolete? Not at all, insists
Mr Collins. "Smith periods are still a very good indication of
blight risk. It's now more important than ever to build
well-timed [fungicide] applications around a realistic
threat-based blight control strategy."
Ensuring decision support systems keep pace with the new blight
strains is a key focus of a new PC-funded research programme,
which aims to improve understanding of how new populations
respond to temperature and humidity. The PC is also
commissioning blight scouts to undertake intensive crop
monitoring and sampling again this year, to aid ongoing blight
population research.
[Byline: Charles Abel]
--
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******
[2] Bangladesh: Rangpur, Rajshahi Division
Date: Mon 23 Mar 2009
Source: The New Nation (Bangladesh), United News of Bangladesh
(UNB) report [edited] <http://nation.ittefaq.com/issues/2009/03/23/news0826.htm>
Potato farmers in Rangpur concerned
This season [2008/09] farmers cultivated potato on 54 000
hectares
[133 500 acres] against the 50 000 hectares [123 500 acres] in
the last season [2007/08] with a view to earn a windfall profit.
But the farmers expressed apprehension that the production may
fall by 30 to 40 percent from the target of 1.134 million metric
tons due to the outbreak of the 'late blight' disease that
damaged potato plants in many fields.
Many educated unemployed youths engaged themselves in potato
cultivation by borrowing money and taking land on lease but
their hopes have been shattered by the late blight disease and
low price in the market.
--
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ProMED-mail
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[Potato late blight (PLB) is caused by the fungus-like organism
_Phytophthora infestans_ and can cause 100 percent crop losses
in potato and tomato. The pathogen is spread by plant material
(including seed tubers), wind, and water. PLB disease management
generally relies on fungicide treatments of seed tubers and
crops.
Considerable variation in aggressiveness between different
isolates of _P. infestans_ has been observed. For more
information on PLB see links and previous ProMED-mail posts
below.
Where both A1 and A2 mating types of the pathogen are present,
reproduction occurs sexually as well as asexually increasing the
chances of strains with higher fungicide resistance and
increased yield losses to develop. A1 is present worldwide, A2
occurs now in northern Europe, northern and central America, and
parts of Asia.
Within each mating type there are a number of genotypes
(strains). In western Europe, a dramatic increase in the
frequency of the A2 mating type is being recorded at present,
with a single lineage apparently accounting for much of the
change in the UK population of strains (see also ProMED-mail
posts no. 20071207.3939 and 20090109.0083).
In Bangladesh, PLB outbreaks have also been reported recently
from other areas (ProMED-mail posts no. 20090310.0989 and
20090121.0255).
While PLB often causes problems in the region, the disease has
been extraordinarily rampant this planting season (2008-2009),
and emergence of new strains with increased fungicide
resistances can also not be excluded.
Smith periods are used as a guide to PLB risk and are defined as
2 consecutive days over 10 deg C (50 deg F) with at least 11
hours a day above 90 percent relative humidity. These conditions
are conducive for sporulation. If they occur at intervals equal
to the generation time of the pathogen there is a greater risk
of disease development.
Maps
UK:
<http://www.lib.utexas.edu/maps/europe/united_kingdom.gif>
and <http://healthmap.org/r/008E>
Bangladesh:
<http://www.nationsonline.org/oneworld/map/bangladesh_map.htm>
and <http://healthmap.org/r/008D>
Bangladesh divisions:
<http://en.wikipedia.org/wiki/File:Bangladesh_divisions_english.png>
Pictures
PLB symptoms:
<http://www.sciencedaily.com/images/2007/01/070102132649.jpg>
(tuber) and
<http://www-biol.paisley.ac.uk/bioref/Chromista/potato_blight.jpg>
(leaves)
Tomato field destroyed by late blight:
<http://www.apsnet.org/online/feature/BioSecurity/Images/lateblightbolkan.jpg>
Microscopy of PLB infected cells:
<http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/brightfield/images/potatoblight.jpg>
Microscopy of sporangiophores:
<http://www-biol.paisley.ac.uk/bioref/Chromista/Phytoph_infestans.jpg>
Links
Late blight fact sheets:
<http://ohioline.osu.edu/hyg-fact/3000/3102.html>
and <http://vegetablemdonline.ppath.cornell.edu/factsheets/Potato_LateBlt.htm>
Disease history and background:
<http://www.apsnet.org/online/feature/lateblit/>,
<http://www.olympusmicro.com/micd/galleries/brightfield/potatoblight.html>,
and
<http://www.agric.wa.gov.au/pls/portal30/docs/FOLDER/IKMP/PW/PH/DIS/VEG/FS0401_REVIEW.PDF>
Late blight information and resources, UK Potato Council:
<http://www.potato.org.uk/department/knowledge_transfer/fight_against_blight/advice_blight.html>
SCRI, UK populations of late blight and A2 distribution:
<http://www.scri.ac.uk/research/pp/pestanddisease/blightepidemiologyandpopulationbiology>
Explanation of Smith periods for PLB prediction:
<http://www.blightwatch.co.uk/content/bw-Smith.asp>
_P. infestans_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=232148>
Global Initiative on Late Blight:
<http://gilb.cip.cgiar.org/>.
- Mod.DHA]
[see also
in the
archive:
Late blight, potato - India, Bangladesh: update 20090310.0989
Blight & undiagnosed disease, potato, chilli - Bhutan
20090211.0612 Late blight, potato - India (02): (WB)
20090131.0435 Leaf blight, potato - Bangladesh: (KH)
20090121.0255 Late blight, potato - Nepal (BR) 20090114.0162
Late blight, potato & tomato: USA (FL), Ireland 20090109.0083
Late blight, potato - India: (PB) 20090103.0018
2008
----
Late blight, potato - Papua New Guinea (02): recovery
20081103.3454 Late blight, potato - India, Canada alert
20080815.2534 Late blight, potato - Bhutan: (TM) 20080811.2473
Late blight type A2, tomato - Taiwan: 1st report 20080615.1891
Late blight, potato - UK: (Scotland), alert 20080430.1482 Late
blight, tomato, potato - USA: (FL) 20080219.0664 Potato diseases
- India: (West Bengal) 20080206.0477 Late blight, potato - Papua
New Guinea: recovery 20080121.0256 Fungal diseases, potato -
Bangladesh 20080107.0091
2007
----
Late blight, potato - India (02): (Punjab, W Bengal)
20071221.4099 Late blight, potato - UK: new strains
20071207.3939 Late blight, potato - India: (Punjab), alert
20071116.3715 Fungal diseases, vegetable crops - Canada:
cucumber, potato 20070730.2442 Late blight, potato & vegetable
fungal diseases - Europe 20070708.2174 Late blight, potato -
India, UK 20070509.1491
2006
----
Late blight, potato - India (Kashmir) 20060424.1200 Late blight,
potato - USA (AK), Bangladesh 20060324.0911 and older items in
the archives]
