April 10, 2006
From: ProMED-mail<promed@promedmail.org>
Source: Democrat and Chronicle [edited]
<www.democratandchronicle.com/apps/pbcs.dll/article?AID=/20060410/NEWS01/604100335/1002/NEWS>

Area farm wages expanding war on potato worm

Larry and Joe Guilian have built their lives around this plot of rich Livingston County soil. As boys, they rushed home after school everyday to work on the family potato farm in the hamlet of South Lima.

But as men, they're facing a challenge their father and grandfather never imagined. The Guilian land is infested with an invasive species, a rare strain of root-eating microscopic worm known to exist on just one other farm in the entire United States.

The combined efforts of 3 generations are at stake, as the Guilian brothers are forced each year to dump thousands of pounds of rotting potatoes that they were unable to sell.

Nematodes are typically introduced as hard brown cysts in the soil.
Once their target prey -- plants such as potatoes, tomatoes and eggplants -- begin to grow, the eggs within these cysts sense a chemical signal indicating that roots are developing. They hatch and start feeding on these roots.

Infested plants rarely die, but they are of little use to farmers, said Bill Brodie, a retired Cornell University professor who researched the pest for years.

Sated, the female nematodes burrow into the roots. Once they're fertilized by the free-crawling males, they swell into amber-colored spheres the size of a pinhead, each filled with eggs. Undisturbed, the process repeats itself over and over again until the soil is teeming with millions of nematodes.

But even if the land is planted with an unsuitable food source, it will remain infested. A nematode cyst can survive for decades in the soil, waiting for the right crop before releasing its 300 or more eggs.

For decades, the story of the golden nematode was heralded as a great success story of invasive species control. The original strain of the pest likely hitched a ride from Europe to Long Island on Army vehicles returning home from World War I.

Problems were discovered on Long Island in 1941, then in western New York -- including the Guilian farm -- by the late 1960s and early 1970s.

The U.S. Department of Agriculture jumped into action, paying farmers as much as USD 150 per acre not to grow potatoes.

Pesticides were applied and, when injected into the soil, were very effective. However, after the chemicals were found in groundwater on Long Island, the practice was discontinued.

Soon, a better strategy emerged. Cornell University in Ithaca, Tompkins County, began working in the 1960s to develop new potato varieties by crossing commercial crops with a wild Peruvian potato naturally resistant to the nematode. They succeeded, and for decades farmers have been required by federal law to grow only these 30 or so resistant varieties on infested land.

Even a small amount of soil can spread the pest, so farmers in quarantined areas were also required to steam-treat their equipment with superheated water between fields and to submit to annual soil tests by state agriculture officials.

The system worked, restricting the nematode infestation to about 17 000 acres in 9 New York counties: Orleans, Genesee, Livingston, Steuben, Seneca, Wayne, Cayuga, Nassau and Suffolk. To date, the golden nematode has not been found in any other state, and control efforts are ongoing.

Jessica Chittenden, a spokeswoman for the state Department of Agriculture and Markets, which enforces the quarantine, cited a new plan to create best management practices for nematode control, and even management plans that are personalized for each farm, to ensure that the pest does not spread.

Despite these precautions, a new nematode strain known as R02 [= Ro2] managed to jump from a single site on Long Island to Livonia then march across the Guilian land. "Half our farm is infested," Larry Guilian said.

Brodie theorized that both strains were introduced at the same time, but the R02 worms couldn't compete against the original strain. Now, with original nematode populations depressed by years of control measures, the R02 can make its move. So R02 could emerge anywhere infested with golden nematode, he said.

The Guilians tried to use the same strategies that had worked against the original strain. A handful of varieties that are resistant to R02 exist, and the brothers have grown them all. A yellow potato called the Sante showed the most promise but ultimately has been a failure.
In the past 4 years, the brothers have dumped 642 000 pounds of potatoes, the bulk of a crop that they raised and harvested but couldn't sell.

Compared to the varieties the Guilians used to grow, Santes were smaller and bruised more easily.

When the R02 strain was discovered 5 years ago, the brothers hoped they could wait out a few bad years while Cornell researchers bred a better potato.

Chittenden verified that a "commercially acceptable" resistant potato is 5 to 10 years away. But as the years pass and research funds shrink, the Guilians are losing hope. The farm has already lost more than USD 160 000.

Despite their precautions, R02 on the Guilian farm has spread from 20 acres in 2000 to at least 60 of the 120 or so acres they plant with potatoes each year.

New York grows about 20 000 acres of potatoes each year, a crop worth USD 42.7 million, according to USDA data from 2004. None of those farms wants to see the infestation spread.

Canadian officials also have been very clear that any indication that New York is losing control over its nematode infestation could result in a complete border closure for any crops that are sold with soil on them, soybeans, potatoes, flower bulbs and nursery plants, Wickham said.

That safety can't be assured without more of a federal commitment to controlling this invasive species, said Wickham, who has spent the past few months lobbying for funding.

Karl Hoffman, who grows about 200 acres of potatoes in Springville, Erie County, said the quarantine is working. Thus far, his area -- about 70 miles west of the Guilian farm -- is free of both strains of golden nematode. But he wants to see funds dedicated to maintaining vigilance and developing new resistant varieties so that the region's farms will have options no matter what happens.

"You don't want (golden nematode) anywhere near you," Hoffman said.
"It's a scary thing. ... It could wipe out life as we know it."

Last year [2005], the USDA's pest control division, known as the Animal and Plant Health Inspection Service, was granted USD 808 000.
But Wickham said that USD 1.268 million is needed for the program to ensure that some funding is directed toward nematode control in New York.

[Byline: Misty Edgecomb <MEDGECOM@DemocratandChronicle.com>]

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ProMED-mail
<promed@promedmail.org>

Soybean cyst nematode - Illinois: new strains
Date: 8 Apr 2006
From: ProMED-mail <promed@promedmail.org>
Source: Belleville.com and Associated Press [edited] <http://www.belleville.com/mld/belleville/news/politics/14297492.htm>

Soybean cyst nematode: A USD 250 million problem that won't go away

Soybean planting in Illinois is just weeks away, and while farmers worry about the possibility of plant-killing rust, some crop researchers are sounding a different alarm: Beware the soybean cyst nematode.

The tiny parasite is found in 84 percent of the state's soybean fields, according to a survey completed last year [2005], and has evolved into a pest that can rob yield even from soybean varieties thought to be nematode resistant.

"We have plenty of farmers getting 50 or 60 bushels (per acre) who should be getting 70 and 80 bushels," says Terry Niblack, a plant pathologist at the University of Illinois who studies soybean cyst nematode nearly full-time.

Nematodes are tiny roundworms, only about 1/64th of an inch long, that suck nutrients from a plant's roots, decreasing its ability to produce beans. And their thievery is invisible; infected plants don't look sick, and unless farmers spend time sampling their soil, they might never know how much they're losing.

"It's a war, not just a battle," says Steve Stierwalt, who grows about 600 acres of soybeans on his farm near Sadorus, in Champaign County.

Yield losses statewide could reach as high as USD 250 million per year, Niblack said. That represents about 10 percent of the total value of Illinois' soybean production in 2004.

Researchers have spent years looking for the best way to control the soybean cyst nematode. In Illinois alone, the state Soybean Checkoff Board provides about USD 250 000 per year to study the pest, said Mary Burke, the board's research director.

But rather than a cure, Niblack and other researchers are finding surprises. The nematodes have remarkable ability to adjust to human intervention.

Soybean cyst nematode was 1st reported in Japan about 90 years ago but likely existed in Asia long before that. Scientists believe the pest was likely introduced in the United States in the late 1800s, even though it wasn't discovered until 1954.

"The nematode has adapted very well to the Midwest," Niblack said.

Over the years, breeders developed soybean varieties that resist the effects of nematodes and keep yield losses under control, said Greg Tylka, a plant pathologist at Iowa State University. Some breeders also have boasted of a cure for the pest, but none has proven effective because of the nematode's adaptability.

And resistant varieties are becoming susceptible. A 1990 survey found about 60 percent of the nematodes found in Illinois were not able to attack any resistant variety of soybean, but last year's [2005] survey found the opposite, Niblack said.

"We've been using resistant varieties now for 15 years across a majority of fields in the state, and now most of our nematodes are able to attack those resistant varieties," she said.

The 2005 survey found an average population in Illinois of 2700 eggs per 100 cubic centimeters of soil, about 5 times the threshold considered harmful, Niblack said.

Many farmers "do have the belief that if they just grow a variety labeled resistant for soybean cyst nematode, that's all they need to do, and that's not enough," she said. "They also need to sample the soil and pay attention to whether the numbers are going up or down, and they also need to find out how good the resistance is in the varieties they're planting."

Farmers can scout for soybean cyst nematode by taking random samples from a 10-acre section of field, mixing them together and sealing some of the soil in a plastic bag to send to a private or university-sponsored soil-testing laboratory, Niblack said.

It also isn't enough to simply rotate corn and soybeans each year in a field, she said. Farmers also need to change the soybean variety they plant "to show the nematode something different each time."

Such rotations have worked for Stierwalt, the Sadorus-area farmer, but he still hopes a way will be found to defeat the nematode.

"We have battles every year, and at this point we're hoping that there'll be something, possibly through the genetic route, that will actually give us something to win the war," he said.

Soybean farmers have spent the past couple years learning all they can about Asian soybean rust, the devastating disease that arrived in the United States in 2004. Many have plans to spend thousands of dollars on fungicides should rust get anywhere near their fields.

"All that money will be lost if they have soybean cyst nematode in their soil and don't manage it properly," Tylka said. "Certainly we want to be on our toes and prepared for the newest, most threatening pest, but let's not forget the fox that's already in the hen house."

[Byline: Jim Paul]

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ProMED-mail
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[The crop plant potato (_Solanum tuberosum_) is susceptible to the potato cyst nematode (_Globodera rostochiensis_, PCN), which is also known as the golden nematode (GN) especially in N. America. It is found in many places where potatoes are grown including Europe (see link for worldwide distribution map). There are 2 species of PCN affecting crops in Europe. The white or pale PCN (_Globodera
pallida_) is now believed to be the more dominant species, while the yellow or golden PCN (_Globodera rostochiensis_) still causes serious losses in some areas. _G. pallida_ is only known in Newfoundland, Canada in N. America but _G. rostochiensis_ is known in New York State in mainland USA and on Vancouver Island, British Columbia and Newfoundland in Canada. Because of an effective US State and Federal quarantine which has been in existence for over 50 years, PCN/GN remains confined to portions of 9 counties within the State of New York (see link for a map of these counties).

The article in item [1] provides a good summary of the steps taken to regulate and stop the spread of the PCN/GN in NY State. It points out that resistant varieties developed especially for this problem and region have been effective. The appearance of a new strain/pathotype
Ro2 of the golden nematode in this area is now causing concern because acceptable resistant varieties for this strain have not been developed. In the absence of resistant varieties, PCN/GN Ro2 may be better able to increase and spread than the old strain. The nematodes only move a maximum of about one m in the soil. Most movement to new localities is by passive transport. The main routes of spread are infested seed potatoes and movement of soil (e.g. on farm machinery) from infested land to other areas. On one farm featured in the article, the Ro2 strain has spread from 20 acres in 2000 to at least 60 of the 120 or so acres planted with potatoes in 2006, according to the grower. The long term consequences for the export of crops to mainland Canada and elsewhere is spelled out in the article.

In Illinois a different nematode, the soybean cyst nematode (SCN)_Heterodera glycines_, is discussed in item [2] for similar reasons, but without the impact and consequences of quarantine and regulation. SCN is a major and common pathogen of soybean (_Glycine max_). Like the PCN, above ground disease symptoms include stunted plants in patches, and below ground the plants have poor root systems. The cysts of the nematode, which are the size of a pinhead, are associated with the roots. Resistant soybean varieties that have traditionally been grown to manage losses associated with the nematode are no longer offering acceptable levels of resistance, presumably because of the selection of new strains of the pathogen.
The lack of clear above ground symptoms other than poor growth means growers need to test the roots of their plants for cysts and their soil for nematode populations if they are to assess the impact of the nematode.

Maps:
NY State, USA:
<http://www.merriam-webster.com/cgi-bin/nytmaps.pl?new_york>
Illinois, US:
<http://www.merriam-webster.com/cgi-bin/nytmaps.pl?illinois>
PCN/GN distribution
<http://www.eppo.org/QUARANTINE/nematodes/Globodera_rostochiensis/HETDRO_map.htm>
New York State PCN/GN quarantine areas
<http://www.aphis.usda.gov/ppq/maps/nematode1-29-04.pdf>
SCN distribution USA
<http://ceris.purdue.edu/napis/pests/scn/imap/scnall.html>

Pictures:
<http://www.inspection.gc.ca/english/plaveg/pestrava/gloros/images/gloros4.jpg>
<http://www.invasive.org/browse/subthumb.cfm?sub=4905&Start=1&display=52&sort=2>
<http://nematode.unl.edu/scn/scnisuf2.jpg>

Links:
PCN
<http://www.eppo.org/QUARANTINE/nematodes/Globodera_pallida/HETDSP_ds.pdf>
<http://www.pestalert.org/viewArchPestAlert.cfm?rid=35>
<http://www.aphis.usda.gov/ppq/ispm/nematode/>
SCN
<http://nematode.unl.edu/scn/scnisu.htm>
<http://www.apsnet.org/Education/LessonsPlantPath/SoyCystNema/top.htm>
- Mod.JAD]

[see also in the archive:
2005
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Potato cyst nematodes - Russia (Kurgan) 20050809.2322 Potato cyst nematodes, Russia (Altai Region) 20050707.1921
2004
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Potato cyst nematodes, survey - UK (England, Wales) 20040106.0056 Potato cyst nematode - Indonesia (Malang) 20040821.2326 Potato cyst nematodes - Croatia 20040830.2420
2002
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Potato nematodes, potato - Czech Republic 20020106.3168 Potato cyst nematode, potato - Hungary 20021012.5538 Potato cyst nematode, potato - Czech Republic 20021228.6141]