6:00am

Sat November 2, 2013
The Garden Report

The Emerald Ash Borer: An Urban Problem for Colorado

The Emerald Ash Borer perched on tree bark
Credit U.S. Department of Agriculture

The Emerald Ash Borer, an Asian insect, has arrived in Colorado; and Boulder was the first place to host it.

Gardener Tom Throgmorton talks about the rise of the Emerald Ash Borer in Boulder.

It was transported to North America probably on some type of wood product. In the upper mid-west it has killed millions of ash trees and has spread through the native ash forests to urban areas. 

With no natural predators in North America, its populations have grown and spread rapidly since 2002. There are some chemical treatments to protect the trees, with the most successful being injections into the tree trunk or soil at the base of the tree, but the treatments are expensive and need to be applied annually. 

The invasive insect has clustered in ash trees at 30th Street and Iris Avenue in Boulder and so far no other infected ash trees have been found within a half-mile radius of the infestation. The Boulder Forestry Department and the Colorado Department of Agriculture will be conducting a survey of ash trees throughout Boulder and Boulder County to determine the extent of the insects’ range.     

The Colorado Department of Agriculture is recommending that ash trees within a five mile radius of the initial infestation be considered for treatment.  Trees should be healthy, with less than forty percent die- back in the canopy and between eight and twelve inches in diameter.

Unlike states like Michigan, where acres of ash forests were destroyed, Colorado’s ash population is mostly confined to urban areas. As a result, the EAB won’t spread through the state like the Mountain Pine Beetle, but people could potentially spread the insect through carrying firewood or untreated wood chips

A quarantine is now in effect for Boulder County, the City of Erie and part of Jefferson County.  This restricts the movement of hardwood firewood, Ash trees and wood chips or trimmings from the quarantine area.  Two landfills in the quarantine area will be able to take wood debris. The Colorado Department of Agriculture has updated information on what to do if you have trees that may be infected.

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