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Emerald Ash Borer


Emerald Ash Borer (EAB) was first identified in Michigan in 2002; since then it has spread to 22 states, including Colorado. It was introduced from East Asia likely through infested shipping or packing material. The most likely route of introduction to Colorado was probably in firewood or nursery stock. EAB impacts all species of ash (Fraxinus spp.), white, purple, green and their cultivars. Colorado has many ash in the urban forest (we estimate about 15% of trees are ash). Boulder has approximately 98,000 public and private ash trees. The Denver Metro area has an estimated 1.45 million ash trees. Some neighborhoods and developments may be up to 80% ash.

What does EAB do?

• Kills ash trees!

• Larvae feed under the bark, eventually girdling the tree and cutting off nutrients.

• Trees are killed within 2-4 years of first symptoms, even previously health trees.

• Trees of all size can be attacked, from 1/2 inch saplings to largest mature trees.

• This insect is very difficult to detect because it is under the bark and the adults are only around from May to September.

EAB Movement

Infestations result from movement of infested ash trees and wood. It does not fly far on its own.

Some of the items it moves on or in:

• Firewood

• Packing material/industrial wood material

• Live plant material (nursery stock etc) • Ash wood such as logs, branches, chips, etc.

Potential Impacts of Emerald Ash Borer to Colorado Communities

Green and White Ash widely planted in Colorado over past 50 years

• Ash comprises 15%-80% of community trees depending on location

• Ash is still planted extensively due to tolerance of urban growing conditions, it is fast growing and has nice fall color

• Green ash is also naturalized along creeks and ditches throughout Eastern Colorado and parts of the Front Range. It has been found along Boulder Creek.

Total ash tree population for Metro Denver is estimated to be 1.45 Million trees Boulder has an approximately 98,000 ash trees

In the greater Denver Metropolitan area in direct economic impact could be:

• Removal of public and private trees approximately $435 Million total

• To replace those trees could cost approximately $580 Million total


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