IDAHO FALLS — Many farmers in Scotland plant potatoes less often than they once did and anticipate a 10 percent yield loss because of the spread of potato cyst nematodes, Scotland’s chief nematologist says.
Jon Pickup shared his country’s PCN woes during a public meeting to underscore the importance of Idaho’s efforts to eradicate the destructive microscopic worms from a roughly 5-square-mile quarantine area of Bingham and Bonneville counties.
“You don’t want the situation we’ve got in Europe,” Pickup said. “Pale cyst nematode is spreading and severely limiting our ability to produce potatoes in the United Kingdom, and it will continue to do that until we have more resistant (potato) varieties and those resistant varieties are accepted by the market.”
Officials at the Jan. 20 meeting said they’re optimistic about Idaho’s outlook based on testing of new PCN treatment methods to replace methyl bromide, a chemical the program abandoned two years ago due to residual levels found in subsequent crops.
Pickup, who participated in an international science review of the U.S. and Canadian PCN management programs, admits he was initially skeptical the outbreak could be contained when Idaho discovered pale cyst nematode in 2007. Pickup now describes Idaho’s program as a “remarkable success,” though he encourages the spud industry to test for PCN in its other major potato production areas, especially in seed, to keep the pest in check.
Pickup said that thanks to good seed program controls, PCN is limited to 30 percent of Scotland’s production area, but it’s spreading quickly, and more resistant varieties are needed.
PCN is the major pest of concern in Scotland and has forced seed growers to expand to six-year potato rotations, he said. Scottish growers who raise spuds for supermarkets that prohibit nematicide use sometimes plant on eight- to 10-year rotations, he said. He said a pale cyst nematode-resistant spud called Innovator has become the most popular global variety.
Tina Gresham, director of the PCN program for USDA’s Animal and Plant Health Inspection Service, has been seeking to build grower support for expanding use of litchi tomato as a trap crop — a plant that stimulates cysts to hatch but isn’t a viable host. Gresham said the program planted litchi tomato on a commercial field with a low PCN infestation during 2015 and 2016 and found no traces of the pest following both seasons.
“That’s the best news I’ve heard about litchi tomato,” said Shelley grower Steve Christensen, who has a regulated field that now has no detectable PCN and is eligible to be replanted to potatoes. “I see it more so now as a possible, very effective tool.”
Gresham said litchi tomato seed production problems in Prosser, Wash., have limited seed supply, leaving enough to plant just 30 acres, and she already has a grower lined up for 2017. Efforts are underway to find a second outlet to expand or sell litchi tomato seed.
Researchers working with the program are also attempting to improve the efficacy of the trap crop and analyze its genes, hoping to confer resistance to new potato varieties.
The University of Idaho’s potato breeding program also has ongoing breeding trials for PCN resistance, and should begin making crosses in the coming year with promising resistant material, including the Dutch cultivar Basin Russet.
Researchers at the meeting also reported success with using mustard meal — with one variety proven to increase hatching rates when paired to a trap crop and another shown to control cysts.
Idaho’s PCN program now includes 9,540 regulated acres, 3,047 of which are considered infested.