It could get very scary walking through the city’s parks and woodlands, a feeling that has nothing to do with clowns or next week’s boo-fest, and everything to do with tiny bugs that have killed thousands of ash trees.
The emerald ash borer, an Asian invasive that arrived in Pennsylvania in 2007 and has spread across the state, has decimated most of the 180,000 ash trees in the city’s parks and they should begin to fall soon, said Phil Gruszka, director of parks management and maintenance policies for the Pittsburgh Parks Conservancy.
“It’s as bad as what we predicted it would be several years ago,” Mr. Gruszka said Tuesday in Riverview Park, “and the dead trees are going to start coming down as their root systems rot away.”
To be clear, no ash have fallen and injured anyone in the city, and conservancy and city parks and forestry crews have worked to minimize the risk by identifying and cutting down dead and dying ash along trails and roads and in city neighborhoods.
“The city has been actively removing the dead trees, but is every hazard tree removed? I can’t say,” Mr. Gruszka said.
An even bigger threat from the dead trees may be to the urban forest’s ability to hold back and store storm water, he said, which will further inundate the region’s already overburdened sewer systems.
The ash borer was accidentally shipped into the U.S. in packing material and was first identified near Detroit in 2002. Since then it has killed more than 20 million trees in Michigan, Indiana, Illinois, Kentucky, Ohio and Pennsylvania, where ash makes up about 7 percent of all trees, but up to 50 percent in some northern tier counties.
But the borer is not the only threat. Mr. Gruszka said. Oak wilt fungus, a native fungus common throughout the Midwest and originally found in city parks in 2010, has since spread throughout every city park. It has also hit oaks hard in the county’s South Park.
“Oak wilt first came to Frick and Highland Park, and now it’s in Schenley and Riverview,” Mr. Gruszka said, and noted that additional threats to forest health are looming.
Beech bark disease has been discovered in a park in Sewickley but hasn’t jumped into any of the city parks yet, he said. And the lantern fly, a plant hopper native to China, India and Vietnam that has the potential to decimate 25 species of hardwoods and fruit trees in Pennsylvania, was found two years ago north of Philadelphia.
“The threats are many and the resources are few,” Mr. Gruszka said. “But we’ve been able to cobble together resources to manage some existing trees and plant new ones.”
The conservancy, which works in partnership with the city to protect and preserve city parks, has spent $28,000 from private donations to treat and save 145 of the best and biggest ash trees, some in each of the city parks.
On Prospect Hill in Schenley Park, where a mature stand of white and red oak was removed, new trees were planted and around a one-acre site, a metal fence was installed to exclude deer, which would eat the young trees.
And on Tuesday in Riverview, 33 volunteers from the Pipitone Group, a marketing agency, worked to weed around treated oaks the group planted last year.
“Volunteers are essential to our work in keeping our parks healthy,’ said Erin Tobin, a parks conservancy community outreach coordinator, directing the volunteers. “Today’s work gives our city the benefits of cleaner air, pollution filtration and healthier greenspace.”
She said volunteers have donated more than 30,000 hours of work in the city’s parks this year.
Don Hopey: dhopey@post-gazette.com, 412-263-1983, or on Twitter @donhopey
First Published: October 19, 2016, 4:00 a.m.
