Any non-treated ash tree alive today will be gone in less than three years, and that timeline is being generous, say Columbia Heights city officials. Having treated or removed all ash trees on their public land, they’re concerned that fewer than 10% of those on private property have been treated for emerald ash borer, or removed, and that it’s too late to save more than half.
The pest of the Midwest has taken hold of Minneapolis’ lush landscape of ash trees, its population growing exponentially since first appearing in Minnesota in 2009. The emerald ash borer originates from Asia and has spread across the globe in recent decades.
The beetle has already devastated ash trees in Michigan and Ohio. The beetle’s spread is accelerated by the transport of firewood by humans, confirmed as the cause through evidence of the beetle’s population bunching along the interstate system. The state of Minnesota has had a ban on the transport of firewood for over the last ten years.
Trees provide many benefits to the community, including energy savings, cleaner air and water, and increased property values. “Just one average-sized ash tree can intercept the CO2 equivalent of burning 50 gallons of gas per year,” said Ryan Spencer, municipal consulting arborist at Rainbow Treecare.
Emerald ash borer larvae attack ash trees by eating the inner bark, limiting the tree’s ability to transport nutrients throughout its limbs—ultimately killing the tree. Some emerald ash borer infestation identifiers are woodpecker activity on the tree—including holes or missing bark, a thinning canopy or dead sections of a tree and “D”-shaped exit holes where newly hatched beetles emerge.
Ash trees can be saved with a chemical treatment. The City of Columbia Heights has worked with Rainbow Treecare to provide residents a bulk discount through 2022 for ash trees on private property that are at least 10 inches in diameter.
The chemical injection needs to be scheduled once every two to three years, and if repeated in that period, treatment can keep the tree alive indefinitely. According to a statement by the City of Columbia Heights, the treatment is 90% effective if done before the beetle digs into the roots, but the majority of residents who have ash trees on their property have yet to take action.
“In Columbia Heights, any non-treated ash tree currently alive today will be gone in less than three years, and that timeline is being generous,” the City of Columbia Heights stated in a press release. The city has preserved 270 of its community ash trees, which will be provided proper upkeep by city foresters.
City Forester Liam Genter, a past research assistant at the University of Minnesota in the field of plant pathology, is in charge of managing the health of city trees. Genter has studied tree diseases and worked with environmental researchers to expand scientific knowledge on how to save endangered tree species.
“I would estimate that less than 10% of the privately-owned ash trees in Columbia Heights have been treated or removed,” Genter said. “That makes thousands of privately-owned ash trees that need to be managed for emerald ash borer, either with preventative treatments or removals. The window for preventative treatment has already closed for 50% or more of the ash trees. Those trees will all need to be removed.”
This spring, the city completed all scheduled ash tree removals on public property. The remaining city-owned ash trees are chemically treated.
“If you drive through Minneapolis, you will see marked ash trees everywhere. If you see a green ring around them, that’s the city ordering the removal of ash trees,” Genter said. “In the city of St. Paul—most of them are gone already. There’s not that many ash trees left.”
Since 2020, Heights has removed around 300 publicly owned ash trees. By the end of 2022, the city will have replaced the removed trees with 500 saplings of multiple varieties to ensure diversification.
“I feel like I’m a doomsday prophet—I’m Chicken Little,” Genter said. “Now the sky is actually falling.”
The city requests that landowners contact the city if they have trouble identifying the species of trees on their property and an expert will come out and take a look.
Mark Peterson did a related story in 2020 that can be viewed here: https://www.mynortheaster.com/news/reports-from-the-ash-borer-battlefields/