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[1] Potatoes stable
[2] Blight monitoring service launched
[3] Potato blight fungus (_Phytophthora infestans_)

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[1] Potatoes stable
Date: Thu 3 May 2007
Source: The Statesman, Calcutta, India [edited]
<http://www.thestatesman.net/page.arcview.php?clid=22&id=182794&usrsess=1>

State agriculture department officials and cold storage owners today insisted that despite drastic fall in potato production, prices will not [increase] much. Due to incessant rain in February [2007], late blight had reduced potato production to 48 lakh ton from the projected 90 lakh ton this year. It is 30 per cent lower than last year's production of 72 lakh ton. So, potato prices are relatively high this year [2007].

The Cold Storage Association president, Mr Sant Kumar Tibrewal, said, "Cold storages in the state have recorded 10 per cent reduction in potato collection." State agriculture department officials said the potato stock is enough to fulfill the demand of 32 lakh ton a year in the state.
Agriculture marketing director Mr T Biswas said, "Prices in the coming months will depend on the supply from south India where potato cultivation starts in late August. There will be a huge scarcity if the production is hampered," he said. Fog, cloud, and rain at the onset of potato harvest are a threat.

--
communicated by:
J Allan Dodds
former ProMED-mail plant disease moderator <dodds@ucr.edu>

[A 'lakh' is a unit in the Indian numbering system, widely used both in official and in other contexts in Bangladesh, India, Nepal, Sri Lanka, and Pakistan. One 'lakh' is equal to a hundred thousand. A hundred 'lakhs' make a 'crore' or ten million. The word is particularly notable because it is used almost exclusively in English articles written for Indian audiences (as opposed to writing "hundred thousand"). - CopyEd.MJ]

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[2] Blight monitoring service launched
Date: Fri 4 May 2007
Source: Farmers Weekly Interactive [edited]
<http://www.fwi.co.uk/Articles/2007/05/04/103426/blight-monitoring-service-launched.html>

Potato growers can now be alerted to confirmed local blight outbreaks and Smith Periods [weather patterns used to predict the risk of blight outbreaks (see link below) - Mod.DHA], after the launch of the British Potato Council's (BPC) new combined Fight Against Blight (FAB) and Blightwatch service.

Once registered at either the British Potato Council at <http://www.potato.org.uk/blight> or Blightwatch at <http://www.blightwatch.co.uk>, users can receive free alerts via e-mail or SMS for up to 10 UK postcodes.

This will allow fungicide programmes to be better tailored to actual blight risk, says BPC agronomist Mark Prentice. "Early warning is a crucial part of keeping this devastating disease under control and reducing the annual BPS 20m (USD 39.8m) fungicide bill growers pay."

There have already been a couple of blight outbreaks in crops under polythene in the south west and a number of Smith Periods have also been recorded, he says. "We don't tend to get much traditional blight until most crops are through. Not many are yet and there's not much inoculum about [due to the dry weather], but it's early days, so there is no need to take your eye off the ball."

Mr Prentice urges growers to stay alert for signs of the disease and control any volunteer potatoes or growth on outgrade piles.

A new set of BPC trials aims to improve blight control by more effectively targeting fungicide doses and timings. The trials will test how blight develops on 3 varieties with different resistance ratings, under a range of fungicide programmes.

Symphonia, which has good resistance, Maris Piper (moderate), and Shepody
(susceptible) will be tested using spray programmes containing different rates of Dithane (mancozeb), Shirlan (fluazinam), and Infinito
(fluopicolide) at 7 and 10 day intervals.

"The products we have chosen represent the 3 new Europe-wide star ratings that fungicides are given -- a standard that reflects their effectiveness and mode of action," explains BPC's Rob Clayton. They also represent a range of costs, which will be built into the results, he notes.

[byline: Paul Spackman]

--
communicated by:
J Allan Dodds
former ProMED-mail plant disease moderator <dodds@ucr.edu>

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[3] Potato blight fungus (_Phytophthora infestans_)
Date: Wed 9 May 2007
Source: Olympus Microscopy Resource Centre [edited] <http://www.olympusmicro.com/micd/galleries/brightfield/potatoblight.html>

Potato late blight, caused by the fungus _Phytophthora infestans_, is one of the most important potato diseases in the world. It was responsible for the great Irish potato famine of the 1840s, which left over 1 million people dead from famine-related diseases and resulted in the exodus of more than 1.5 million people from Ireland.

Native to South America and cultivated by Native Americans for thousands of years, the potato plant was introduced to Europe by the Spaniards in the mid-1500s. Although it was probably already carrying milder forms of the late blight fungus, it was not until 1844 that the virulent strain (speculated to be a single clonal genotype of _P. infestans_) arrived in Ostend, Belgium, via a shipment of infected seed potatoes from the United States. Within 2 years, potato crops in continental Europe, as well as in Ireland, were ravaged.

Disease outbreaks are caused by vegetative reproduction (self-cloning) of the fungus and require cool temperatures and moist conditions. Controlling the fungus is difficult because it has a complicated life cycle with distinct and strikingly different spore forms, ranging from motile zoospores (produced by self-cloning) to thick-walled oospores (produced by sexual reproduction). As occurred in 1845 in Ireland, blight can overwinter in unharvested potatoes and release its airborne spores the next season as the new potato stalks grow.

With the emergence of a new strain in the United States during the 1990s, late blight continues to be a looming threat to the world's potato crops.
The new strain is virulent and remarkably destructive, devastating apparently healthy potato fields within days. Within hours after the fungus contacts a healthy plant, normal potato plant leaves can be transformed into badly damaged leaves. The recent strain reproduces under lower humidity, making it a threat to potato crops in more arid regions, such as the high mountain valleys of Colorado and Idaho. Prevention through seed piece treatment with fungicides and destruction of cull piles appear to be feasible prevention measures for this economically-devastating fungus, which can overwinter on other hosts such as the bittersweet and hairy nightshade.

[byline: CD Kelly, TJ Fellers, MW Davidson]
--

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

[_P. infestans_ can also affect other solanaceous crops such as tomato or eggplant. Considerable variation in aggressiveness between different fungal isolates has been observed.

The report of a 50 per cent crop loss from India is a reminder of the constant threat of potato late blight worldwide. Unfortunately, the latest technology as employed in the UK to support local growers, is not available for all!

There is a second potato leaf blight called 'early blight', which is caused by the fungus _Alternaria solani_.

Pictures:
diseased tubers:
<http://www.sciencedaily.com/images/2007/01/070102132649.jpg>
microscopy of infected cells:
<http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/brightfield/images/potatoblight.jpg> 

leaf symptoms:
<http://www-biol.paisley.ac.uk/bioref/Chromista/potato_blight.jpg>
microscopy of sporangiophores:
<http://www-biol.paisley.ac.uk/bioref/Chromista/Phytoph_infestans.jpg>
Links:
information about late blight:
<http://www.potato.org.uk/department/knowledge_transfer/fight_against_blight/advice_blight.html> 

information about and history of potato late blight:
<http://www.apsnet.org/online/feature/lateblit/>
explanation of Smith period for disease prediction:
<http://www.blightwatch.co.uk/content/bw-Smith.asp>
information on US sites:
<http://www.ndsu.nodak.edu/instruct/gudmesta/lateblight/>
description of potato late and early leaf blights:
<http://www.ag.ndsu.edu/pubs/plantsci/hortcrop/pp1084w.htm>. - Mod.DHA]

[see also in the archive:

2006
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Late blight, potato - India (Kashmir) 20060424.1200 Late blight, potato - USA (AK), Bangladesh 20060324.0911
2003
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Late blight, potato - Papua New Guinea 20030306.0554
2002
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Potato late blight, potato - Canada (Newfoundland) 20020818.5091
2001
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Phytophthora infestans, potato late blight - Russia 20010620.1177 2000
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Potato late blight, global research efforts 20001031.1903 Potato late blight: global initiative 20000516.0765
1996
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Potato late blight: global threat 19960617.1123]

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