Disease threatens a valuable Pennsylvania lumber source

In this article from the Philadelphia Inquirer, Davey's Chris Miller tells readers that thousand cankers disease has the potential to become a devastating problem to the state's black walnut trees.

By Allison Steele

Posted: August 10, 2014

As trees go, black walnuts are the superheroes of Pennsylvania's forests. Strong and resistant to most aggressive insects and sickness, their lumber is among the most valued in the state.

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But arborists and forestry officials are battling what they say is green kryptonite to that black walnut population: thousand cankers disease, a deadly and incurable illness that has emerged in the region for the second time in recent years, and that some say poses a grave threat to the state's $19 billion hardwoods industry.

"It absolutely has the potential to be disastrous," said Chris Miller, an arborist with the Davey Tree Expert company, which has offices in King of Prussia and Bryn Mawr. "The long-term impact could be, eventually, no more black walnut. There are very few diseases that seem to affect them, so this is really a game-changer."

Spread by tiny beetles the size of poppy seeds, thousand cankers starts beneath the bark and eats away at the tree until its limbs wither.

The beetles, which officials say can travel about two miles each year, carry fungus that they leave behind when they burrow into tree bark. Cankers eventually form in the place of the burrows, and, as more beetles tunnel in, the tree becomes unable to take in nutrients. By the time its leaves start thinning and turning yellow, it's too late - any tree that has been infected dies a slow death that can last up to 10 years.

On Monday, the Pennsylvania Department of Agriculture announced an infected walnut twig beetle had been found in southwest Chester County, followed by traces of the disease in nearby trees.

Continue reading about thousand cankers disease.

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