Ash: the Long Goodbye
White ash at Stroud Preserve
A few years ago, a forester discovered what is believed to be the tallest American chestnut tree in its native range, from Maine to Mississippi. The 95-foot tree is located in woodlands in a small town in southwestern Maine. About 100 years ago—when one in every four hardwood trees in North America’s eastern forests was an American chestnut—this tree would have been decidedly unremarkable. But, in 1904, a strange fungus was found on the chestnut specimens at the Bronx Zoo; by 1940, most mature chestnuts had been wiped out by the blight.
Staff members Tom Kershner and Darin Groff inject an ash tree at Binky Lee Preserve in an effort to stave off emerald ash borer.
Photo: Caleb Arrowood
The number of large surviving trees within the American chestnut’s former range is probably fewer than 100, but among them researchers hope to find the key to re-establishing this majestic tree species. By crossing old survivor chestnuts like the specimen found in Maine to one another, scientists aspire to breed a pure American chestnut with blight resistance.
Tom Kershner, Natural Lands’ arborist and tree management coordinator, is thinking of the future of another native tree species as he drills a small hole to insert a tap at the base of a white ash growing along a trail at our Binky Lee Preserve in Chester Springs. Once the tap is installed, Kershner injects a pesticide called Tree-age into the cambium layer where it will be taken up by the tree’s vascular system and protect it (hopefully!) from emerald ash borer.
An Asian insect first identified in Detroit, Michigan, in 2002, emerald ash borer has become the most destructive forest insect to ever invade the U.S. It’s now one of the most damaging pests ever seen in North America—comparable to the chestnut blight and Dutch elm disease. There are 16 ash species and an estimated eight billion ash trees in North America; all of them are susceptible. In southeast Michigan, scientists have documented 99 percent mortality in infested trees.
In 2007, the emerald ash borer invasion was noted in western Pennsylvania and has been moving steadily east ever since.
Natural Lands’ approach to this new threat is a pragmatic one. Across our 22,000-acre preserve network, we are systematically taking down ash trees that are likely to become hazardous when they die—those that are within 100 feet of a road, building, parking lot, or location where people would congregate or rest, such as a bench or kiosk. “Dead ash trees become brittle very quickly and become dangerous,” says Kershner. “We take our role as stewards of these preserves seriously and, unfortunately, that sometimes means taking down trees. Sadly, with emerald ash borer, it looks like we’ll be taking down a lot of trees.”
If circumstances dictate, we are taking a more drastic approach. In 2016, a two-acre grove of ash trees at Hildacy Preserve was proactively removed and sold for lumber. Though gut-wrenching, the decision was not a difficult one. “We’re in the business of preserving and planting trees, not logging them,” says Tom Kershner. “But a dead tree has little timber value. Since these trees will all die soon, it’s better to log them now and use the proceeds to restore the area.”
Tom Kershner injects this ash specimen with a pesticide called Tree-age.
However, we’ve also identified notable, robust ash specimens at our preserves to inoculate and save, if possible. The injection equipment and chemicals needed to protect ash trees from infestation are expensive, and therefore it’s not feasible to treat all of the hundreds-of-thousands of ashes on our land. “The hope is that we can inoculate a few special and hearty trees against the borers so they can serve as a seed source for future ashes,” Kershner says.
Although emerald ash borer will have a significant impact on our preserves, the vast majority of our forests have the diversity to survive the borer’s punch and continue to provide important environmental, ecological, and recreation benefits.
For more information on emerald ash borer and options for homeowners, visit the PA Department of Conservation and Natural Resources site here.