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Date: 30 Jun 2007
 
[1] Pale cyst nematode, potato - USA (Idaho): search for origin
[2] Wart disease, potato - USA: control strategies
 

[1] Pale cyst nematode, potato - USA (Idaho): search for origin
Date: Fri 15 June 2007
Source: Fresh Plaza, Associated Press report [edited] <http://www.freshplaza.com/news_detail.asp?id=3345>


USDA seeks origin of Idaho potato pest

American scientists are using DNA comparisons to try to find out how a microscopic wormlike pest that attacks potato plants made its way into this country -- an infestation that last year [2006] closed some foreign markets to US growers.

The United States Department of Agriculture's [USDA] Nematology Laboratory in Beltsville (Maryland) has compared the DNA of the potato cyst nematodes found in April 2006 in south eastern Idaho (ID) with other populations and discovered a close match with nematodes in York, England and the Netherlands. The Idaho outbreak is believed to be the 1st time the pest was detected in the US.

But there hasn't been enough DNA testing on nematode populations around the world to draw any conclusions about the geographic origin of the nematodes in Idaho, said Dr David Chitwood, research leader of the lab. "It may provide helpful clues, but as far as absolute conclusions, it really is difficult," he said. The worms feed at the roots of potato plants and can reduce crop production by 80 per cent. Officials say the pest is not harmful to humans and doesn't have any effect on the potatoes themselves.

The nematodes were found at an Idaho potato processing plant, and after the lab in Beltsville identified them as potato cyst nematodes, they were traced back to fields in south eastern Idaho's Bingham County. The fields remain quarantined, and the USDA is spending USD 11 million on a plan to eradicate the nematodes from about 950 acres (about 385 hectares) in the nation's top potato-producing state.

Idaho grows about one-third of all the potatoes in the US, producing more than 12 billion pounds of potatoes last year [2006], worth about USD 712 million to farmers. The discovery of the nematodes sent a shock through the industry. "You just wouldn't expect (potato cyst nematodes) in the middle of the state," said Frank Muir, president of the Idaho Potato Commission, which promotes Idaho potatoes. "It's not like these guys crawl or fly or anything."

Chitwood said nematodes are spread through infected plants or soil.
Theories of how the nematodes arrived in Idaho range from early immigrants planting gardens to surplus military equipment that wasn't adequately cleaned returning from Europe after World War II. Farm equipment brought in from outside the region has also been considered. Idaho officials say one reason they can't determine the source is that they may have arrived decades ago. "The farmers who farmed the land at the time have retired or passed away," said Mike Cooper, deputy administrator at the Idaho Department of Agriculture.

After the nematodes were discovered last year [2006], Japan banned all fresh US potato imports, and Canada and Mexico banned all fresh potato imports from Idaho. Earlier this year [2007], Canada and Mexico lifted their bans. Japan still bans fresh potatoes from Idaho, but accepts them from other states.

Efforts to eradicate the nematodes in Idaho began earlier this year [2007] when the 950 acres (about 385 hectares) of infected fields were fumigated and covered with tarps. The fields have since been planted with oil radish
-- which officials said deters potato cyst nematode growth -- and another fumigation is planned in the fall. Testing after the 1st fumigation showed the nematodes remained, and killing them could take years. "The thing on the side of the nematode is it can live in the soil for several years without a host," said Chitwood. "But the bad thing for the nematode is that it does not have very many plants that it can reproduce on."

Chitwood said potato cyst nematodes spread from South America, where potatoes originated, to Europe. He said he was a bit surprised they were not found in the US before last year [2006], but that border inspections and care in transporting seed potatoes likely delayed their arrival. How they arrived remains a mystery. "I think we'll never know who done it on this one," said Muir.

[byline: Keith Ridler]

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

[2] Wart disease, potato - USA: control strategies
Date: Tue 19 June 2007
Source: Science Daily, American Phytopathological Society (APS) report [edited] <http://www.sciencedaily.com/releases/2007/06/070618102406.htm>

While many may be familiar with potato late blight, the plant disease responsible for widespread potato shortages, the lesser known potato wart has the potential to be as devastating to economies that depend on potato production, say plant pathologists with the American Phytopathological Society (APS).

According to Gary Franc, plant pathologist with the College of Agriculture, Plant Sciences Department at the University of Wyoming, potato wart is a serious disease of cultivated potato that has been detected worldwide. Potato wart is caused by the fungus _Synchytrium endobioticum_, which is considered to be the most important worldwide quarantine plant pathogen of potato. While not harmful to humans, the disease causes unsightly growths that initially appear white, and then turn brown or black as they decay, rendering the potato tuber unrecognizable and inedible. A cross-section of a potato wart gall on a tuber reveals that galls result from an overgrowth of tuber tissue. The potato wart pathogen reproduces within gall tissue.

There is a zero tolerance for the fungus that causes potato wart. As a result, this disease has been placed on the USDA's "Select Agent List" of plant pathogens deemed to pose a severe threat to plant health or to plant products. Although direct losses from potato wart may be insignificant when 1st detected, indirect economic losses resulting from zero-tolerance regulations for potato wart can be devastating to growers. This becomes especially evident in areas that are subject to quarantine measures, as well as when the movement of commercial potatoes is restricted.

Spores released from infected plants can make soil unsuitable for potato production for decades. The long term survival of fungal spores and the lack of suitable chemical controls for potato wart suppression make this disease especially problematic for any type of potato production, from small garden plots to extensive land areas economically dependent on production of potatoes for consumption or for seed tubers.

"Potato wart is much easier to prevent than it is to control," Franc said. "It is highly critical that we prevent the introduction of the potato wart pathogen to production areas and, where it is already introduced, to limit its spread," he said. "While regulatory action is important in potato wart management, it is essential that research efforts continue with the goal of developing and improving reliable and integrated disease suppression methods to directly deal with this disease," said Franc.

(Note: This story has been adapted from a news release issued by the American Phytopathological Society)

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

[The nematode referred to in item [1] is pale cyst nematode (PCN; _Globodera pallida_), which is classed as a very high risk to potato producing areas. Other hosts include tomato and many species of _Solanum_. Spread occurs via soil, plant debris, and infected potato tubers. It is widespread in Europe and parts of South America and also present in a few locations in Asia.

Another related potato nematode, golden cyst nematode (GCN; _G. rostochiensis_) has a similarly high impact and is spread in much the same way. It is even more widely distributed than PCN and has already been found at a few sites in northern America.

Cultivated radish (_Raphanus sativus_) and 'oil' radish (_R. sativus_ subsp. _oleifera_) have been reported to be effective in the biological control of some nematodes when used for intercropping or crop rotation with nematode host plants.

The potato wart fungus _Synchytrium endobioticum_ is considered to be the most important pathogen of potato. It is endemic in Europe and also reported from some other locations (see distribution map). The fungus is spread with soil and by infected seed tubers. Resistant potato cultivars have been developed, but new pathogen strains are emerging compromising the efficacy of host plant resistance. Disease management is based on the control of pathogen spread.

Potato late blight is caused by the fungus _Phytophthora infestans_ and 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.

Maps
Worldwide distribution of PCN:
<http://www.eppo.org/QUARANTINE/nematodes/Globodera_pallida/HETDPA_map.htm>
Worldwide distribution of potato wart:
<http://www.eppo.org/QUARANTINE/fungi/Synchytrium_endobioticum/SYNCEN_map.htm>
US states:
<http://www.census.gov/geo/www/us_regdiv.pdf>
Pictures
_G. pallida_ cysts:
<http://www.niab.com/jdd/public/images/pcn-pop1.jpg>
PCN field symptoms on potato:
<http://www.dowagro.com/uk/images/PCN-damage-potatoes.jpg>
Nematodes:
<http://zeldia.cap.ed.ac.uk/nematodeESTs/species/GPC.jpg>
_R. sativus_ subsp. _oleifera_:
<http://www.pheromone.ekol.lu.se/klubb2000/bilder/oljerattika.jpg>
Potato wart symptoms photo gallery:
<http://www.defra.gov.uk/planth/pestnote/pwd.htm>
Links
Information on _G. pallida_:
<http://nematode.unl.edu/pest5.htm>  and
<http://plpnemweb.ucdavis.edu/nemaplex/taxadata/G053S1.HTM>
Diagnostic test for _G. pallida_ versus _G. tabacum_:
<http://www.ars.usda.gov/is/pr/2007/070627.htm>
_R. sativus_ information:
<http://plants.usda.gov/java/profile?symbol=RASA2>
Radish in nematode control:
<http://www.bioasialink.net/meetingPDF/Seminar2/BSM%20in%20Organic%20Agr%20China%202006.pdf> 

News story 'Oil radish knocks down nematodes in eastern Idaho potato field':
<http://news.ag.uidaho.edu:591/News/FMPro?-db=AgNews&-lay=generic&-format=story.htm&NewStoryID=204&-find> 

APS potato wart feature June 07:
<http://www.apsnet.org/online/feature/potato/>
Potato wart news story, CropBiotech update, 22 Jun 2007:
<http://www.biotechknowledge.com/BIOTECH/knowcenter.nsf/ID/587EEEBA982F03258625730200587D39?OpenDocument> 

Potato wart disease information:
<http://www.defra.gov.uk/planth/pestpics/qic2004/QIC67.pdf>
USDA toxin list:
<http://www.aphis.usda.gov/programs/ag_selectagent/ag_bioterr_toxinlist.shtml>
_S. endobioticum_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=120395>.  - Mod.DHA]

[see also in the archive:
Pale cyst nematode, potato - US (ID): quarantine update 20070418.1282
2006
---
Pale cyst nematode, potato - USA (04): quarantine measures 20060915.2607
Pale cyst nematode, potato - USA (03): 2nd report 20060805.2161
Pale cyst nematode, potato - USA (02) 20060615.1657
Quarantine Pests, New Data - EPPO (02) 20060531.1521
Pale cyst nematode, potato - USA: 1st report 20060423.1195
Potato wart disease - Turkey (Ordu Province): 1st report 20050406.0990
2003
---
Plant pests, new data, EPPO 20031204.2986
Potato wart disease - Estonia: eradicated 20030731.1872
2002
---
Potato wart disease - Canada (PEI) (02) 20020907.5253
Potato wart disease - Canada (Prince Edward Island) 20020906.5243
2001
---
Potato wart, potato - Canada (Prince Edward Island) 20011229.3136
2000
---
Potato wart disease - Canada (P.E.I.): EPPO report 20001225.2276
Potato wart disease - Netherlands 20001118.2016
Potato wart disease - Canada (P.E.I.): USA import ban (02) 20001104.1919
Potato wart disease - Canada (P.E.I.): USA import ban 20001102.1908
Potato wart disease - Canada (Prince Edward Island) 20001028.1877
Potato wart disease 20000211.0191]

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