Living with plum pox
Canadians opt for containment program in Ontario. Eradication continues in New York.
Jim Bittner, pictured with a tour group in his New York orchard, pulled out 20 acres of peaches when a plum pox-positive tree was found in his orchard. He is worried about Canada dropping its eradication effort.
PHOTO BY RICHARD LEHNERT
The question of how plum pox should be managed has long been subject to international disagreement, but not on the North American continent—until now.
Until last year, Canada and the United States were in general agreement. They would attempt to eradicate the disease whenever it appeared. Last year, Canada announced that it would abandon its ten-year-old eradication effort and opt instead for a containment program.
Can a containment program coexist alongside the eradication program that is continuing in the United States? The two areas currently dealing with plum pox, while in two different countries, are in fact one area—eastern Ontario and western New York, the stone fruit orchards of which are separated only by the Niagara River. There are orchards near the river on both sides.
Getting answers from government officials was not easy or satisfying. Questions designed to elicit science-based answers from scientists at the United States Department of Agriculture’s APHIS (Animal and Plant Health Inspection Service) or the Canadian Food Inspection Agency were deflected to media relations departments and treated as matters of high-level diplomacy between nations (see “Canadians will reduce pressure to eliminate plum pox”).
But in the orchards, growers on both sides of the border, who consider themselves friends and neighbors, are quite willing to discuss the matter. Both sides agree: It was not a good move by Canada’s federal government.
Phil Tregunno, the new president of the Ontario Tender Fruit Producers Marketing Board, a grower organization, said, “We were effectively abandoned. After a lot of time and effort, we got about 90 percent of the way there, and they abandoned us,” he said of the Canadian government’s decision. “They didn’t ask our opinion.
“We’ll be living with uncertainty. We don’t know what will happen. The program we had was working, and we were close to success.”
Tregunno has about 700 acres of fruit along the Niagara River. He’s 19 miles as the crow flies from Singer Farms in Appleton, New York, where Jim Bittner also has an opinion. Bittner lost 20 acres of peaches, pulled out and destroyed when a plum pox-positive tree was found in his orchard. He’s still two years away, at least, from being released from a quarantine under which he can’t plant plums, peaches, or apricots on his farm.
“I may have to find land outside the quarantine area,” he said. “I need to keep my plantings up-to-date if I’m going to stay in the stone fruit business.”
Bittner said growers in New York are very concerned. “We just don’t know,” he said. “Will the concentration of the virus in Ontario increase? Probably so. So, the risk of an aphid carrying plum pox to us will increase.
“On the other hand, aphids are not very efficient at spreading the plum pox virus. Can they fly across the Niagara River, or will they be swept out into Lake Ontario by the wind that goes with that huge outflow of water?” Niagara Falls might be an effective barrier.
It is not known today how the various plum pox infections in Pennsylvania, New York, Michigan, Nova Scotia, and Ontario began, but infected budwood is the likely source, and the various sites did not infect each other.
A bit of history
Plum pox was first discovered in Bulgaria in 1915, and since then, it has spread over much of the world. There are an estimated 100 million infected trees in Europe. There are two strains of the virus, and the one found in North America is strain D, which does not infect cherries but does infect all other stone fruits.
The virus is not easy to detect, and it takes some time to build up to where symptoms appear and it reduces yields, produces deformed fruit, and saps the tree. Meanwhile, infected trees are sources of infection for other trees visited by aphids that carry the virus. Most American growers, even those like Bittner who has lost orchards, have never seen any symptoms of the disease other than test results.
When the virus was found in Pennsylvania in 1999, a decision was made by the U.S. Department of Agriculture that, since it affected a limited area, it should be eradicated. It would not be lived with, as it is in most of the world. The major concern then was that it would be devastating if it invaded the almond and peach orchards of California.
Plum pox was found in Ontario in 2000.
Before eradication was complete in Pennsylvania, two other outbreaks occurred in the United States, both in 2006, when one infected tree was found in Michigan and a few (about five total) were found in New York.
Mike Hansen, an official with the Michigan Department of Agriculture who worked with APHIS, said an eradication program is a huge undertaking. A statewide sampling program was initiated that has taken 350,000 samples—and is still going on. Only one infected tree was ever found—but it led to the destruction of thousands of trees, many of them in Bill Shane’s peach-breeding program near Benton Harbor.
The Canadian decision will not directly affect Michigan, Hansen said. Michigan is upwind, not downwind, as is New York. The virus is vectored by aphids and also in budwood from infected nursery stock. The budwood situation has changed dramatically.
Bittner said it used to be common practice for peach growers to share budwood with other growers. “We can’t be swapping budwood,” he said. “We just can’t do that anymore.” Now growers plant certified virus-free trees.
Aphids are another matter. If temperatures continue the warming trend, Bittner said, aphids could be of increasing concern in New York and Ontario in the future.
The key problem in Canada, our sources agree, is the concentrated nature of the stone fruit industry on the Niagara Peninsula. Bittner noted that orchards in New York are scattered, while in Ontario they are close together.
In the eradication program in the United States, when an infected tree was found, that tree was eliminated and so were all others within 500 meters. “If they had used the Pennsylvania model, they’d have taken out 90 percent of the peaches in Canada,” Hansen said.
So Canada tried a modified approach, taking out fewer trees around infected ones. Still, the Canadian effort was massive compared even to the one in Pennsylvania.
“I have to give them credit, they took out a lot of trees,” Bittner said.
In fact, by last March, the Canadians had spent $180 million in the eradication program and had taken out about 355,000 trees, and had eradicated plum pox in a small pocket of infection in Nova Scotia. The ongoing monitoring program in Ontario was finding fewer and fewer positive trees, and these were systematically removed.
By comparison, the U.S. program in Pennsylvania and New York cost about $40 million and took out 1,675 acres of trees in Pennsylvania.
The federal and Ontario governments estimated in 2007 that not moving to eradicate plum pox would cost the fruit industry $114 million over the following 25 years in lost yield and quality, probable restrictions on border movement, and the disease’s likely spread across Canada. For Ottawa to monitor the disease, it would cost about $900,000 per year, indefinitely.
But last year, the Canadian government apparently decided the existing program cost too much, and eradication would give way to containment. The new program has a federal budget of $17 million over the next five years.
To Bittner, the major drawback to the new Canadian plan is that growers within the area have no incentive to test or remove trees. So, if infected trees are there, the virus can build up. “They’re just testing on the fringe. If they find infected trees, they’ll just move the [quarantine] line.”