Losing Their Crowns
Pine trees in Swanzey forest face a destructive invader
By Anika Clark
Keene Sentinel Staff
Published: Monday, July 06, 2009
Decades before he would donate roughly 70 acres of land in Swanzey to the Society for the Protection of New Hampshire Forests, Paul E. Dickinson had his eye on the threat of natural disaster.
“My interest in the Society goes back some time — to when Mr. (Edgar Clarkson) Hirst was State Forester,” he said in a letter he wrote to the Concord-based organization in the late 1960s. “… I was a schoolboy, and sent to him from this same lot samples of White Pine weevil twigs, and asked him to identify and recommend treatment.”
Fast forward to 2009, when a rampant but under-researched fungal disease called caliciopsis canker has taken hold of the forest.
“We’re growing one type of wood here, which is white pine, and so it’s really troubling because it’s going through the whole stand,” said consulting forester Swift C. Corwin Jr. of Peterborough. “I would say that 65 to 70 percent of the trees are showing outward signs of the disease.”
Similarly concerning, according to D. Jackson Savage 3rd — the forest society’s vice president for communications and outreach — is that as of last year, forest society staff had no idea the disease was such a problem in the Joseph and Mary Dickinson Memorial Forest.
“It seems like the thing is really moving and affecting the trees quickly,” Corwin said.
Standing among looming white pines and swarming mosquitoes last week, Corwin — who will be working on a timber harvest in the forest all summer — recalled when he was first alerted to the outbreak.
“I got a call. … ‘Do you know (about) the infestation of the caliciopsis?” he remembered. “I said, ‘No.’ And I came out here and said, ‘Oh geez.’ ”
Despite its recent identification in the Dickinson Forest, caliciopsis canker — or pine canker — likely existed there for at least a decade, said Kyle D. Lombard, a forest entomologist with the N.H. Division of Forests and Lands.
The fungal disease was first reported in New Hampshire 12 years ago, according to a Division of Forests and Lands fact sheet.
The fungus attaches to a tree through open or flimsy spots in the bark. Healthy trees can section off the infected portion of the tree, grow over it and remain relatively unharmed, according to Lombard.
But in weaker trees, it’s a different story. More spores are produced. Parts of the trees form cankers — or sunken, dead areas — that can merge together, while sap bleeds from the lesions.
Meanwhile, the dead lesions disrupt the movement of nutrients through the tree. And as more and more of the important parts of the tree die, Lombard said its crown — the foliage portion — becomes sparse.
The good news for the timber industry, according to Lombard, is that the microscopic fungal spores tend to congregate in the upper regions of the tree where the bark is thinner and the wood’s less valuable.
Corwin also described the fungus’s effect on timber value as minimal.
“It doesn’t seem to affect the quality of the wood, “he said, “until it gets to the point where the tree is dead and the bark is falling off.”
But, he added, “The growth of the trees is really being affected by this thing.”
Signs of this were evident throughout the Dickinson Forest last week.
“That’s the disease right there,” Corwin said, looking at a cluster of trees whose crowns stretched sparsely against the sky.
“The needles within the area that ought to be live crown have thinned out and sort of inexplicably disappeared,” he said.
The fungal spores affix to the trees using short, hairlike projections Lombard said act somewhat like Velcro in their ability to attach themselves to passing insects or small animals.
The spores can also be swept along by wind and rain.
So what can foresters and state officials do?
At this point, Lombard said, the best defense is simply to cut down infected trees.
“Right now, the best we can offer is to suggest that people try to change the environment around those trees by doing thinnings,” he said, a tactic that has seemed to work at other infested sites.
Last harvested in 1993, the Dickinson Forest was on tap for a timber harvest anyway, according to spokesman Savage. The poor timber market could have been a reason to hold off, he said, but the disease pushed the society to go ahead with the harvest in spite of low wood prices.
Also in response to the pine canker, Corwin said he’s harvesting a bit more than he otherwise would have and is focusing on creating larger openings between the remaining trees.
This, he said, will likely encourage new tree growth. It will also increase air flow, reducing the moisture that helps the fungus thrive.
Still, he described forest management, in general, as something of a gamble.
In the meantime, he said, “There are a whole lot of things about this disease that aren’t known.”
Cheshire County Forester Steven S. Roberge said he has seen pine canker numerous times in his work for the University of New Hampshire Cooperative Extension.
“We don’t really know … where it came from, why it’s here … nor do we know the best management for it,” he said.
Among questions swirling around the disease is how great of a threat it poses to the Granite State’s forests.
While saying he believes the disease probably exists throughout southern New Hampshire at this point, Lombard said, “how severely this affects the future of our white pine stands is completely up in the air.”
Roberge noted how valuable white pine is as a fast-growing, productive species.
“If it were to go pretty suddenly, the forest industry would be kind of turned on its head,” he said. However, because the fungus is relatively weak in the sense that healthy trees often can ward it off, he said this would probably be a slower process.
Another unknown is the connection — if any — between pine canker and the feathery lichen Corwin said he’s seen spreading across several infected trees.
Lombard called the association “completely a mystery.
“Nobody really has any idea what that relationship is or even if there is one,” he said. “I think if somebody had the research dollars and time, it would be an interesting project.”
Another question, according to Lombard, is whether there’s any correlation between recent droughts — which can strain trees and make them more vulnerable to infections — and the onset of caliciopsis in infected forests.
But don’t expect state officials, already busy with threats such as the Asian longhorned beetle, oak leafroller and hemlock woolly adelgid, to come up with the answers anytime soon.
Asked if the state has money for more in-depth research on pine canker, Lombard’s response was simple.
“Oh God, no,” he said. “We have just enough money to put gas in our vehicles to go look.”
Anika Clark can be reached at 352-1234, extension 1432, or firstname.lastname@example.org.