New Tree Disease Detected Near Doylestown

Doylestown residents should be on the lookout for signs that a new and swift-moving tree disease has moved into their neighborhood.

Thousand Cankers Disease sounds like a painful affliction – and it is, for the black walnut tree.

Previously found only out west, the disease has been detected in Bucks County, the Department of Agriculture confirmed on Tuesday.

To slow the spread of the disease, the department has issued a quarantine on black walnut trees, logs, lumber and firewood.

So far, the disease and the insect that carries it has not shown up in Doylestown, but it has been found nearby and experts say it is only a matter of time.

“It’s moving, and it’s spreading extremely quickly,” Bob McMullin said Friday. McMullin, who lives in Doylestown, is president of and is the arborist for Doylestown Borough and Township. “It’s spread by an insect, and the interesting thing is, up until last fall, it hadn’t been found anywhere but in the western states.”

Thousand Cankers Disease is caused by the walnut twig beetle, which carries a fungus. As the beetle burrows beneath the bark of walnut trees, it spreads the fungus, causing small cankers to form, according to the department of agriculture. Repeated attacks cause cumulative damage to the tree, disrupting its ability to channel water and nutrients.

Typically, the tree’s branches begin to die, and the tree itself usually dies within 10 years, the department said. There is no known way to cure the disease or combat the beetle, it said.

The disease was first described in the western United States in the 1990s. In 2010, it was confirmed in Tennessee, and about three weeks ago, it was found in Virginia.

“It’s probably being spread by the movement of infected wood,” McMullin said. “That’s almost surely why they quarantined it, because to have it leapfrog from the west to Virginia to Pennsylvania in such a short time is unusual.”

To try to slow the spread of the disease-carrying insects, Agriculture Secretary George Greig on Wednesday signed a quarantine order for black walnut in Bucks County.

The quarantine means nurseries and lumber mills no longer can sell black walnut trees, logs or milled wood to customers outside Bucks County.

It also means that firewood that may have been chopped from a black walnut tree cannot be taken out of Bucks County. Because most people can’t distinguish black walnut from other hardwoods, the order applies to all hardwood firewood, the department said.

Both restrictions will affect businesses in Bucks County, McMullin said.

“There are significant impacts of this problem,” he said. “Places like the lumber mills north of Doylestown that might deal in black walnut logs might have a customer in Stockton, New Jersey. They can’t sell the logs to them anymore, they have to keep them in Bucks County.

“And there are plenty of people who sell firewood locally, on a large scale, and wholesale it out to someone in Flemington, New Jersey, for example. It appears they won’t be able to do that now.”

Few nurseries in Bucks County grow the tree to sell, McMullin said, so it’s unlikely to impact the nursery business.

The black walnut tree, which is native to the Eastern United States, makes up less than half of one percent of hardwood trees in Pennsylvania, the department of agriculture said.

But because its wood is so highly prized, the trees are important to the state's $25 billion hardwoods industry, it said.

Black walnut is particularly valued in the woodworking and furniture-making fields, and was a favorite of New Hope artisan furniture maker George Nakashima.

A set of four captain's chairs by Nakashima made of black walnut, for example, sold for $1,500 at the auction house Christie's in December.

Nakashima also created a "peace altar" out of black walnut to mark the 50th anniversary of the United Nations in 1995.

Black walnut nuts, too, are eaten by both humans and wildlife.

As for Doylestown residents, McMullin said they need to be careful, too.

“Black walnut does grow around Doylestown and Doylestown Township,” he said, “so people should keep an eye on their trees.”

Trees can be infested with the walnut twig beetle for years before showing signs of distress. Watch for leaves that turn yellow and twigs and branches at the top of the tree that start to die and fall off; both are early symptoms of the disease.

As the disease progresses, larger limbs die, followed by the tree's trunk.

To report signs of Thousand Cankers Disease, contact the Bucks County Cooperative Extension office at 215-345-3283 or BucksExt@psu.edu, or the state's Invasive Species Hotline at 1-866-253-7189 or Badbug@pa.gov.