ITHACA, N.Y.—Across Cornell’s campus, workers carefully injected a powerful insecticide into the base of 65 ash trees over the course of Wednesday and Thursday. It’s the only thing keeping these trees alive.
Ash tree populations have been declining for years since the introduction of the emerald ash borer to North America from East Asia in 2002. Without any natural predators, the invasive insect’s larvae have been digging under the bark of ash trees, and feeding on the tissues of the tree. The result of the unmitigated feasting is the gradual, but fatal disruption of the tree’s ability to move nutrients and water through its vascular system. The insect’s kill count is estimated in the millions of ash trees.
“Right now, there’s nothing other than us intervening that could save ash trees,” said Joe Aikan of Arborjet, a private company that donated its treatment services to Cornell University as a part of its Saving America’s Iconic Trees program.
Employees from Arborjet traveled across Cornell’s campus with employees from the university drilling holes into the base of the ash trees, making a pressurized injection of pesticide, and then plugging up each hole.
The technique and the specific pesticides have been in commercial use since 2008. The ash trees that are sustained this way need to be re-treated every 2 to 5 years, said Aikan.
Joe Doccola, Director of Research and Development at Arborjet said that, unlike a pesticide that would be sprayed onto a tree which can result in other insects being killed, the injection treatment targets the emerald ash borer’s larvae.
“You’re minimizing off target hits,” said Doccola, “Off target is anything else that feeds on the tree that might be targeted that you don’t intend, and so this is a reduced risk.”
Administering the injections is a time consuming process, making it a difficult technique to scale. The ash trees that can be saved are chosen carefully. The ones selected might be mother trees in a forest — the largest, and oldest trees — or, in the case of those on Cornell’s campus, feature prominently on the grounds of the university.
Emma Gutierrez, a Natural Areas Steward with the Cornell Botanic Gardens, “We can’t treat all of them. We really tried to make a point of selecting ones that were in iconic locations for students to be able to see, for visitors to see.”