Oak wilt continues to spread

The affected area in Highland Park as it looked last year

A while back we told you about how the oak wilt fungus claimed two acres of trees in Frick Park.  Unfortunately, the fungus has now been spotted in two other regional parks, and by the time the summer growing season is done Phil estimates we’ll have lost about ten acres of red and white oaks in the parks.

Phil says he was suspicious of seven trees in Highland Park last year that looked symptomatic of the disease, but it was too late in the growing season to tell.  This spring when he went back to the same area (behind the DPW materials storage area across from the swimming pool), he saw green leaves tumbling out of trees.  Within a few weeks, City Forester David Jahn had mobilized a firm to remove the diseased trees.  In all, about 35 mature trees came down this July. 

The difference in the area is striking–it’s now almost barren-looking where last year there was an impressive tree canopy.  This area was just starting to look presentable, too–volunteer days over the past several years had removed an almost absurd amount of debris, including dozens of shopping carts.  The area overlooks the Allegheny River and the Highland Park Bridge, and a new trail created as part of our trail and signage improvement project was helping to make this sheltered spot a little more accessible. 

After removal of diseased trees

It’s discouraging to see that the early successional species are already beginning to jump in to the area left bare by the trees, which unfortunately in this case means the highly invasive Japanese knotweed.  The Parks Conservancy and the City are putting together plans for stabilizing and re-vegetating the soil, and native seed mixes should be sown there soon which will hopefully help reduce the spread of the knotweed.  Future volunteer efforts in the area will be focused on replanting the slopes.

Riverview Park is up next, with trees set to come down on the hillside adjacent to the Chapel Shelter.  It’s upsetting to see these trees come down, but the quicker they are removed after the fungus is detected, the better our chances of stopping its spread to other trees and forcing even more deforestation.

You can help prevent oak wilt in your own trees by not trimming them from April to October.  Wounding trees during the growing season makes it easier for the fungus to spread.  If you have any questions about oak wilt, you can give us a call at 412-682-7275 or the City Forester at 412-422-6655.