1. Globodera Alliance detail
2. USDA on Pale Cyst Nematode

New weapons in the battle against the pale cyst nematode — a major potato pest that has cost farmers millions of dollars since it was found in southeast Idaho in 2006 — include an effective bio-fumigant and a surprisingly efficient “trap crop.”

Researchers are also making progress in developing PCN-resistant potato varieties.

“Understanding the biology allows us to target the weak point in the life cycle,” said University of Idaho Associate Professor Louise-Marie Dandurand, project director of the Globodera Alliance.

Globodera is the genus of the potato cyst nematode.

The alliance is a five-year, $3.2 million project funded by USDA to assess the risk of and work to eradicate potato cyst nematodes. The 16 alliance members include researchers and educators from the Northwest, New York, Canada, Scotland and France. An advisory board includes industry representatives and federal and state regulators. The project, in its final year, is seeking funding to continue its work.

Cysts with viable eggs, which can number in the hundreds, can persist in the soil for decades. There they remain relatively resistant to chemical and biological stresses, an alliance newsletter said.

The group also studies the golden nematode — found in New York, where resistant potato varieties are available — and the related Globodera ellingtonae, which as yet lacks a common name.

Dandurand said G. ellingtonae has been found in Oregon and a couple of Idaho locations, but does not appear to reduce potato yields. Alliance members are studying it because it behaves like the golden nematode.

“When we see invasives, the whole industry becomes at-risk,” she said.

Pale cyst nematode is of particular concern because it can reduce yields substantially, and resistant potato varieties are not yet available for Idaho, where PCN for years has been the target of government-ordered eradication.

“These encysted eggs can survive in soil anywhere from 20 to 30 years,” Dandurand said. If they have a host plant, the nematodes will hatch, swim to the potato plant’s root, invade it, “and reproduce to form more cysts that contain anywhere from 300 to 500 eggs.”

A 2016 study by UI Agricultural Economics and Rural Sociology Professor Chris McIntosh found PCN cost Idaho $25 million that year in potato farm-gate revenue, lost jobs and other impacts. The loss would have been about $30 million if not for replacement crops like barley and wheat. Non-host crops like grains can be planted in fields where PCN is present if equipment is sanitized per federal standards.

USDA on Jan. 10 announced deregulation of five Idaho fields, a total of 404 acres, after surveys showed no PCN. That brought the total regulated area to 7,150 aces, 3,446 of which were infested.

The agency’s Animal and Plant Health Inspection Service said that in North America, PCN also is present in Newfoundland, Canada.

Dandurand said models show PCN can reduce potato yields by 40-80% where it is present in high densities among potatoes lacking resistance. In the United Kingdom, where the pest is endemic and primarily controlled by planting resistant varieties, yield losses are 9-10%.

She said that when the alliance formed nearly five years ago, “every potato was susceptible. We’ve made great strides toward development of resistant potato varieties.”

“We are really looking for potatoes that do not allow any reproduction of PCN,” Dandurand said. Cross-breeding some U.S. and European potato germplasm shows promise in developing resistance.

Some pathogens can be controlled by rotating with a non-host crop, but this doesn’t work for PCN, she said. “If a grower just plants wheat, PCN just lies dormant for many years.”

Researchers have found that Litchi tomato is a “trap crop” that causes the nematode to hatch, just like potato. “But unlike potato, it does not let the nematode reproduce,” Dandurand said. “After Litchi tomato, populations of the nematode are reduced by 95-100%.”

PCN eradication strategies have included field quarantines and fumigation, and enacting phytosanitary standards. The fumigant methyl bromide was phased out about five years ago.

Alliance researchers found that a mustard-seed meal extract is an effective bio-fumigant to kill the nematode. Dandurand said that when water is added, it breaks down into isothiocyanate, a volatile compound that kills PCN.

Dandurand grew up on her family’s Vermont farm, where “I was really interested in plants and agricultural crops, but didn’t really know about plant pathology,” she said.

She became interested in the discipline as an undergraduate volunteer in a laboratory at the University of Vermont.

Occupation: Research associate professor, Department of Entomology, Plant Pathology and Nematology, University of Idaho. Project director, Globodera Alliance.

Age: 61

Hometown: Lives on a small farm near Moscow, Idaho. Grew up on dairy farm near Franklin, Vt.

Education: B.A., botany, University of Vermont, 1981; M.S., plant science, University of Connecticut, 1985; Ph.D., plant pathology, University of California-Riverside.

Family: Widowed (husband Guy Knudsen, a UI soil microbiology professor and fellow Globodera Alliance member, died in 2016), two grown children.

Hobbies: Gardening