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Forest Pathologist Dale Bergdahl is an expert in the butternut tree and the canker that's killing the species<br />Photo by Jane Lindholm
Forest Pathologist Dale Bergdahl is an expert in the butternut tree and the canker that's killing the species
Photo by Jane Lindholm

Researchers hope for a "super" butternut tree

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Butternut trees are dying across the northeastern U.S. and southeastern Canada. A fungus is killing the big trees much like Dutch elm disease killed American elms over the last century. And just as scientists are producing resistant elms, butternut researchers hope they'll be able to produce a "super" butternut that will fight off the canker killing the old native trees.
VPR's Jane Lindholm, as Part of NPR's Local News Initiative and collaborative environmental reporting among public radio stations in the northeast, has the story.

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Kathleen Osgood Dana walks into the forest surrounding her home in Northfield, Vermont. She stops in front of a huge tree stretching high above the forest floor. "This butternut was here when my family moved here in 1956. And the butternuts dominated this entire hill so my father named it Butternut Hill," she said.

As a child, Dana collected the nuts to make maple butternut ice cream. Her kitchen cabinets are made out of the hardwood. But over the years she's watched this tree, like others on the hill, slowly die. "If you look up this left trunk, see it's still trying to make some leaves up there. But this right trunk has died entirely. You look up and it's all dead."

What's killing Dana's butternuts is an invasive fungus called butternut canker that has infected almost the entire native population east of the Mississippi. Vermont forest pathologist Dale Bergdahl is an expert on the disease. Pointing to an infected tree in a park in northern Vermont, he says the disease is easy to spot. "You'll get these areas of dark discoloration, kind of like soot, on the bark, oozing from these areas of infection. A single canker's not a big issue," Bergdahl explains.

But over time, multiple cankers surround the tree and essentially strangle it. Bergdahl and a team of scientists from around the northeast are trying to develop a new strain of butternut that will resist this disease. Like a detective, Bergdahl is searching for the few butternuts that are still thriving despite the disease. He travels all over New York and New England taking samples. But it turns out identifying a butternut tree isn't so easy.

Sandra Anagnostakis, a scientist at the Connecticut Agricultural Experiment Station is one of the researchers working on the restoration project. "What we're finding," Anagnostakis says, "is that in Northern Vermont, most of the trees are butternut. The further south we get, say in Massachusetts, half of them were butternuts and half of them were Japanese walnuts or hybrids. In Connecticut almost all the trees were hybrids or Japanese walnuts."

The reason for the discrepancy could lie in economic differences that once divided the region. In the 1800s Americans began importing Japanese walnut trees. The walnut is easier to crack than the butternut. But northern farmers couldn't afford these trees. "Whereas anybody who was in the affluent New York, Connecticut, New Jersey area probably would have seen trade magazines with advertisements for Japanese walnuts and heard the raves about what wonderful trees they were and would have been apt to spend their money on getting a few of them," Anagnostakis says.

The hybrid offspring of those walnuts are now making scientists' job more difficult. All butternut samples have to be sent to a plant geneticist for identification. When they find a pure butternut, scientists graft its branches onto black walnut root stock. If these new seedlings can resist the deadly butternut canker, they will be bred into super butternuts that can begin to re-grow the population. But Anagnostakis says that will take at least a decade.
"Well, you have to think in tree time here. Nothing to do with trees is ever very fast."

Back in Northfield, Vermont, Kathleen Osgood Dana is willing to wait. Samples from two of her remaining butternut trees were taken last winter.
"I don't know that any of the materials that we have from these living butternuts are going to be any good. But if they are, that's a legacy," she said. A legacy she hopes will continue on her property on Butternut Hill for her grandkids to enjoy.
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