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[1] Downy mildew, cucumber - Canada (Ontario)
[2] Late blight, potato - Canada (PEI)

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[1] Downy mildew, cucumber - Canada (Ontario)
Date: 18 Jul 2007
Source: Tillsonburg News [edited]
<http://cgi.bowesonline.com/pedro.php?id=301&x=story&xid=324380>

Downey mildew confirmed in Norfolk

This could be another challenging summer for people who like to make their own pickles. The Ridgetown campus of the University of Guelph has confirmed the return of downey mildew to cucumber patches in Norfolk County. The fungus devastated the province's cucumber crop last year [2006] and is a threat to melons, squash and pumpkins as well.

Though downey mildew has been confirmed in Elgin, Norfolk and the Leamington areas, crop officials are optimistic that the latest outbreak can be contained. "The outbreak now is nowhere near what it was like last year at this time," Elaine Roddy, a crop specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs, said. "But it is out there. This is an ugly reminder that we have to maintain an intensive spray campaign and do what we can to protect our crops."

OMAFRA [Ontario Ministry of Agriculture, Food and Rural Affairs] has
36 scouts in southern Ontario monitoring crops for downey mildew. The outbreak in Norfolk has been traced to a commercial cucumber field that has been spraying for the fungus.

Farmers are better prepared this year [2007] to do battle with downey mildew. The Pest Management Regulatory Agency (PRMA) in Ottawa pre-approved the fungicides Tattoo C and Tanos for use this spring.
Downey mildew had destroyed many fields last year by the time these sprays were available. As well, PMRA approved a third fungicide -- Ranman -- for use on vine crops last Friday [13 Jul 2007]. Ranman is normally used to control blight on potatoes. It has proven effective in American trials on downey mildew. "It's a good product and we're glad to have it," Roddy said.

Downey mildew is normally a problem in the American south. However, strong summer storms last year swept spores into southern Ontario.
Local farmers had never been confronted with downey mildew before.
Some cucumber growers lost half their production. Processors had to contend with shortages.

The fungus put strong upward pressure on cucumber prices sold at farmers markets. Herb Bodnar of Villa Nova, a vendor at Simcoe's Farmers Market, said cucumber prices will rise 3 or 4 times above the historical average again if the fungus is as bad as it was last year [2006]. "There was a shortage last year," Bodnar said. "The price went up and no one wanted to pay it. This means there could be no cucumbers again this year."

A vendor who asked not to be identified said diseases like downey mildew put farmers and vendors in a difficult position. On the one hand, customers want pesticide-free produce at an affordable price.
On the other, they want that produce to be bug- and defect-free. It's a tall order, she observed. "You're damned if you do and you're damned if you don't," she said.

[Byline: Elaine Roddy]

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

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[2] Late blight, potato - Canada (Prince Edward Island)
Date: 19 Jul 2007
Source: Canadian Broadcasting Corporation News [edited]
<http://www.cbc.ca/canada/prince-edward-island/story/2007/07/19/blight-july.html>

Late blight hits P.E.I. potatoes

With 3 cases of late blight reported on Prince Edward Island (P.E.I.) on Thursday [26 Jul 2007], the province is warning potato farmers to act quickly to stop the fungus from spreading. One case was found in each county, in Kensington, Morell and O'Leary. Marlene Clark of the provincial plant disease diagnostic laboratory in Kensington told CBC News it is important for farmers to take quick action. "When you have one case in an area, there's obviously more," said Clark. "It's important for the farmers to bring in the samples, call their neighbours to let them know they do have late blight and then adjust their [pesticide spraying] programs accordingly."

Clark said plants from the infected areas have been pulled up and bagged, along with surrounding plants which are assumed to be infected as well but not yet showing symptoms. She added there are reports of numerous piles of cull potatoes across the province and they can be a source of the blight spores. Those piles, she said, must be buried to prevent the spread of the fungus.

Late blight starts on the leaves of potato plants and spreads down to the potato tuber, making it inedible. The fungus thrives in warm, damp conditions. The province had issued a warning to farmers about late blight earlier in the week, anticipating problems after warm, damp weather through the spring and summer.

Blight is best known as the cause of the 19th-century Irish famine.
Modern pesticides generally prevent blight from causing crop failure, but the presence of blight will mean more spraying of pesticides, and higher costs for farmers.

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

[Downy mildew on cucurbits is caused by the fungus _Pseudoperonospora cubensis_. Different strains with variable host preferences
(pathovars) seem to exist. _P. cubensis_ is found worldwide, but it is usually most damaging in tropical and subtropical areas. By affecting the leaves and thus the photosynthetic potential of its host it reduces yield and fruit quality, and it can eventually kill the host plant. It survives on cultivated or wild cucurbit species and is spread by wind, rain, and mechanical means. Disease development can occur over a wide temperature range under conditions of high humidity. Control strategies include the use of resistant cultivars and fungicide applications.

The related species _P. humuli_ causes a serious disease of hops.
Downy mildews in other genera affect grapevine, sunflower, and a number of vegetable crops. Generally, each fungal species is confined to a number of host species.

Potato late blight is caused by the fungus _Phytophthora infestans_, which can also infect other solanaceous crops such as tomato or eggplant. It affects leaves as well as tubers and is spread by plant material (including seed tubers), wind and water. Other fungi and bacteria often invade blight-infected tubers resulting in total tuber breakdown. Considerable variation in aggressiveness between different isolates of _P. infestans_ has been observed.

_P. infestans_ was responsible for the Irish potato famine in the late 1840s, which resulted in large-scale population loss from that country due to deaths and emigration.

For more information on potato late blight and cucurbit downy mildew see also the earlier posts listed below.

Maps:
Canada:
<http://www.lib.utexas.edu/maps/americas/canada_pol_1986.gif>
Prince Edward Island:
<http://atlas.nrcan.gc.ca/site/english/maps/reference/provincesterritories/prince_edward_island/
referencemap_image_view>
Ontario:
<http://atlas.nrcan.gc.ca/site/english/maps/reference/provincesterritories/ontario/referencemap_image_view>

Pictures:
Downy mildew on cucumber leaf:
<http://www.ag.ohio-state.edu/~vegnet/news/currentvn10-06_files/image002.jpg>
Photo gallery of downy mildew on cucurbit species:
<http://www.ces.ncsu.edu/depts/pp/cucurbit/images.php>
Late blight symptoms on potato tubers:
<http://www.sciencedaily.com/images/2007/01/070102132649.jpg>
Late blight symptoms on potato leaf:
<http://www-biol.paisley.ac.uk/bioref/Chromista/potato_blight.jpg>

Links:
Cucurbit downy mildew, disease information and control strategies:
<http://web.aces.uiuc.edu/vista/pdf_pubs/927.pdf>  and <http://www.avrdc.org/LC/cucurbits/downy.html>
Cucurbit downy mildew pathotypes:
<http://www.ces.ncsu.edu/depts/pp/cucurbit/thedisease.php>
_P. cubensis_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=120276>.
Potato blight, disease information, history and background:
<http://www.apsnet.org/online/feature/lateblit/>  and <http://www.agric.wa.gov.au/pls/portal30/docs/FOLDER/IKMP/PW/PH/DIS/VEG/FS0401_REVIEW.PDF>
Potato blight advice and information resources:
<http://www.potato.org.uk/department/knowledge_transfer/fight_against_blight/advice_blight.html>
_P. infestans_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=232148>
OMAFRA
<http://www.omafra.gov.on.ca/english/index.html>  - Mod.DHA]

[see also in the archive:
Late blight, potato & vegetable fungal diseases - Europe 20070708.2174 Downy mildew, cucumber - USA (OH, MI), Canada (ON) 20070704.2120 Late blight, potato - India, UK 20070509.1491
2006
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Downy mildew, cucumber - Canada (ON), USA (MI) 20060803.2149 Late blight, potato - India (Kashmir) 20060424.1200 Late blight, potato - USA (AK), Bangladesh 20060324.0911
2003
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Downy mildew, squash - Italy (Latium, Umbria) 20030401.0803 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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