Stowing away in wooden shipping materials, the emerald ash borer sneaked into Michigan from northeastern Asia around 2002. Since then, it has spread from the Upper Midwest, where it has devastated urban landscapes, to as near as Boulder County, where it was discovered in 2013.
About the Emerald Ash Borer
The emerald ash borer is a small green beetle native to northeast Asia. Female beetles lay eggs in bark crevices in ash trees and the larvae feed under the bark before emerging as adults a year or two after hatching. In its native area, the beetle doesn’t cause significant damage, but in Europe and North America, where ash trees are denser and haven’t developed natural defenses, the beetle is invasive and has devastated tens of millions of trees.
Adult beetles begin to emerge from trees in late spring and feed for about a week on ash leaves before mating but cause little damage in the process. Males hover around trees, locate females by visual cues, and drop directly onto the female to mate.
A typical adult female lives around six weeks and lays 40–70 eggs, but some females live longer, laying up to 200. The eggs are deposited in bark crevices and cracks and hatch in about two weeks. After hatching, J-shaped larvae chew through the bark to feed on the inner parts of the tree until they pupate and mature. Mature beetles chew through the bark to emerge the following spring. By then enough damage has been done to the host tree to eventually kill it.
The emerald ash borer has already killed tens of millions of ash trees in the US and threatens 8.7 billion more throughout North America. The economic impact is especially high for urban and residential areas due to treatment or removal costs and decreased land value from dying trees. These costs are estimated to be as high as $25 billion if all the ash trees become infested and have to be removed and replaced, with most of the cost being born by property owners and municipalities. This makes damage control and prevention a top priority among foresters and arborists nationwide.
How Big is the Threat Locally?
With an estimated 1.45 million ash trees in the Denver metro area, state forest service officials say an emerald ash borer infestation could affect up to one of every six trees in the area and cause as much as $82 million in damages. Denver hopes to avoid it by educating private property owners, where over 90% of ash trees are located. In anticipation of the Emerald Ash Beetle migrating to Denver, Denver Parks & Recreation has launched the Be a Smart Ash campaign to educate property owners of the dangers posed by the beetle. As of the moment, the forestry department of Denver Parks and Recreation hasn’t detected traces of the beetle in the city, but with infestations of the beetle—which has no natural predators— as close as Boulder and Longmont, the Denver city forester says the time to start preventive treatment is now.
What Can Be Done to Keep the Emerald Ash Borer
Systemic treatment of the trees is the best defense against the emerald ash borer. If you have ash trees on your property, call Donovan Arborists at 303-623-8733 or send us an online request for more information regarding this treatment and to learn the best approach to protecting your landscape from this emerging threat.
For more information about the emerald ash borer and its threat to Denver, see our FAQs About the Emerald Ash Borer.