Pittsburgh has removed nearly 200 large oak trees from its parks in an attempt to curtail the spread of a fungus that is killing oaks across the northeastern United States, officials said.
The most recent outbreak of oak wilt was discovered along Prospect Drive in Schenley Park, forcing the city and Pittsburgh Parks Conservancy to cut down 58 trees, said Phil Gruszka, the conservancy’s director of park management and maintenance policies.
About 138 oaks have been removed from Frick, Highland and Riverview parks since the fungus invaded Pittsburgh about eight years ago, he said.
“Once a tree is infected, there is no cure other than to remove that tree,” he said. “It’s tragic that we incur such a loss of these trees.”
The fungus is spread by beetles that feed on sap infected with oak wilt spores. The bugs transmit the spores to healthy trees. Infected trees can spread wilt through roots that intermingle with healthy tree roots.
Pittsburgh trenched around the infected trees with a backhoe to sever the roots.
Gruszka said infected trees drop green leaves that are very dry and feel like paper. He said a visitor to Schenley, who had read about the symptoms, reported the infected park oaks.
“We haven’t had reports of this disease elsewhere, but the more people become informed, the better we’re going to be at managing it,” Gruszka said.
City Forester Lisa Ceoffe said the U.S. Park Service gave Pittsburgh a $60,000 grant to deal with oak wilt. She said removal of Schenley Park trees will cost about $42,000.
Gruszka said a contract for tree removal requires the oaks to be chipped so bark is separated from the wood, which exposes the fungus and kills it. It cannot be used as firewood.
Contractors typically sell it for mulch or manufacture of particle board, Gruszka said.
“Once it’s chipped and the bark is separated, it’s safe for other uses,” he said.