The Emerald Ash Borer, the most destructive, exotic bug ever to invade North America, is devastating the green ashes in the yards and streets of Rapid City and Casper, and it is coming here. The invasive Asian bug selects only green ash trees and, unchecked, will kill more than 8,000 green ashes along Helena’s boulevards within 15 years of arriving at our gates. The arrival of the EAB is inevitable, but mitigation is possible. Educating ourselves is critical.
The EAB is designated an “exotic” invasive species because there are no predators or competitors, biological or otherwise, that can halt its incursion. Since arriving in the Great Lakes region in shipping pallets or crates in 2002, the EAB has killed more than 200 million ash trees in 33 states and three Canadian provinces, that’s 12.5 million trees per year on average. This sounds outlandish, but for objective, empirical info from a state that has been hit real hard.
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Roughly 90 percent of Helena’s boulevard trees are green ashes. Imagine driving the length of Rodney and having no shade trees bowered over the street. The city of Helena has no budget anticipating this imminent threat. So, as an unrecognized problem, of course, we have no plan. Folks reading this might deny it as a back-burner deal, but it really is the most destructive pest ever to invade our continent and it’s knocking on our door.
Preparation and mitigation are possible. Smart timing is essential and depends on identifying the bug’s arrival. As soon as the bug shows up within 15 miles, there are soil-drenching or tree-inoculating measures that must be taken, depending on the size of the green ash and the micro-climate where the tree lives. The effective systemic toxins that can save your green ashes are not mammal-friendly, and should only be applied by trained, licensed pest-control companies. The conventional wisdom on the heels of this ongoing, continental scourge is to seek and act upon the advice from folks with experience. The forestry professors and arborists at Iowa State University have studied and published green ash survival strategies in the wake of such a recent pestilence, and that info is at your fingertips on the above mentioned website.
Three notable symptoms of the EAB, upon arrival are:
1. Thinning, bared-off upper reaches of a green ash tree. That means the bugs are up there feeding on the greenery. Canopy die-off will look much more extensive than normal atrophy. Thinning, bared-off canopies are the most obvious and earliest clue that the whole town needs to know as soon as its presence is detected.
2. Study your Green Ash in the spring and early summer for “D” shaped holes set on their side, like a “Lazy D” brand ¼-inch wide. That means that the larvae successfully over-wintered after burrowing galleries under the bark that impede the flow of moisture and nutrients from the soil. That means you must begin acting during the current growing season to save your tree. In our climate, a treatment can protect your tree for two years, and then subsequent, bi-annual applications are required, seemingly for the life of the tree, at a cost of roughly $16 per stump inch.
3. Should you notice suckers at the base of a Green Ash with leaves several times bigger than the leaves on the tree, that tree is becoming stressed and declining and is trying to gather more sunlight. Time to have a licensed professional treat your tree.
Upon the first signs that EAB is here, tree owners can fight back. A kind of sharp-edged facet of mitigation, however, is that the most effective systemic toxin that is used to treat EAB is that it is also toxic to mammals.
Helena homeowners will have to respond swiftly and decisively to save their green ashes once the bugs arrive. The city of Helena should acknowledge the inevitability of this destructive bug’s arrival and prepare to deal with the thousands of boulevard trees that so beautifully shade our streets and contribute to Helena’s “Queen City” ambiance.
Chris Daly, the city of Helena lead arborist, is certain the bugs will show, it’s just a matter of when.
“It will be catastrophic,” Daly said. “Currently, our replacement plans include diversifying the species and age of boulevard trees. And it is no longer even legal to plant a green ash.”
Tom Harpole is a retired arborist, journalist and traveling teacher in Alaska’s Bush Schools.