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It's fungus, not fall, that's causing leaves to drop in Western Pa.

Renatta Signorini
| Friday, Sept. 7, 2018, 9:54 a.m.
Fallen leaves accumulate on Lincoln Avenue in Edgewood, Allegheny County.
Jason Cato | Tribune-Review
Fallen leaves accumulate on Lincoln Avenue in Edgewood, Allegheny County.
An example of anthracnose on a sugar maple leaf.
Pennsylvania Department of Conservation and Natural Resources
An example of anthracnose on a sugar maple leaf.
An example of anthracnose on a sugar maple leaf.
Pennsylvania Department of Conservation and Natural Resources
An example of anthracnose on a sugar maple leaf.
Kayla Bottino, 20, does school work while on a bench surrounded by fallen leaves at Pittsburgh’s Frick Park on Sept. 6, 2018.
Nate Smallwood | Tribune-Review
Kayla Bottino, 20, does school work while on a bench surrounded by fallen leaves at Pittsburgh’s Frick Park on Sept. 6, 2018.

Fall is coming, but that isn’t why so many leaves already are on the ground in many parts of Western Pennsylvania.

A fungus on some maple and white oak trees in the Pittsburgh region is causing leaves to develop black spots or shrivel up and drop early. It’s the result of an unusually wet start to the year, agreed Celine Colbert, a forester in the Forbes State Forest district, and Phil Gruszka, director of horticulture and forestry at Pittsburgh Parks Conservancy.

“All of these happen when you have cool, wet weather in the spring,” Gruszka said.

Both reported seeing fungus-related issues affecting trees and leaves in northern Westmoreland County and Allegheny and Butler counties. Fallen maple leaves line the streets in Pittsburgh’s East End neighborhoods and municipalities like Edgewood. The problem is prevalent in northern Allegheny and southern Butler counties, Gruszka said. Spots that look like black tar on maple leaves also have been seen in Pittsburgh parks.

It’s a problem in Erie and through much of the state that has caused “extensive damage” on chestnut oaks in the western two-thirds of the state, as well as hickory, red maple and birch trees, said Thomas Hall, a forestry pathologist with the state Department of Conservation and Natural Resources.

“It’s causing leaves to curl up and drop off the tree,” Hall said of chestnut oaks, adding that he believes wet weather the last few years has played a role. “Each year it gets worse.”

The leaf disease — anthracnose — is affecting the maple and oak trees in different ways in pockets of the Pittsburgh region. Maple trees can “look a little rough and drop their leaves” and the leaves on some oaks appear crinkly or like the edges had been burned, Colbert said. Her observations were made in the Forbes State Forest district, which includes Allegheny, Greene, Fayette, Washington, Westmoreland and Somerset counties.

“We’ve seen it throughout the district, particularly Allegheny and the northern parts of Westmoreland we’ve been seeing the worst,” she said.

The disease is “pretty noticeable” in the Cranberry and Evans City areas, Gruszka said.

“Anthracnose on white oaks was pretty severe this year,” he said.

It’s not a disease that spreads from tree to tree, and it should die off during the winter, Colbert said, adding that it doesn’t affect people. The fungus is always present, but worsens with wet weather.

Residents or others who suspect trees in their areas may have the disease should clean up the leaves to prevent the fungus from reproducing and spreading. The leaves should not be mulched by a lawnmower and left in grass, Gruszka said.

Leaves should return as normal next year with no lasting impact, Colbert said.

Renatta Signorini is a Tribune-Review staff writer. You can contact Renatta at 724-837-5374, rsignorini@tribweb.com or via Twitter @byrenatta.

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