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Emerald Ash Borer in Colorado

The Emerald Ash Borer (EAB) has been found in Boulder. It was discovered by City Forestry staff this past September. The EAB attacks all species of Ash and has close to 100% mortality rate for all untreated trees. Therefore everyone who has ash trees will most likely be faced with the decision to have their Ash trees removed or treat them through the duration of the infestation, which is estimated to last 13 years.


Early warning signs to watch for include:


If I have an Ash tree, what should I be doing?

The first step is to determine wether you want to save your Ash tree. It may be more cost effective and easier to replace a young tree or remove an older tree in poor health and start over with a new tree.

I don’t want to loose my trees?

The Emerald Ash Borer will cause close to 100% mortality for all Ash trees.If you want to preserve your ash trees than treatment will be necessary. Speak to a professional to find the best treatment for your tree.

What should I do now?

Find out if you have Ash trees first. And get a professionals oppinion on the state of your Ash tree. Then you can make a better decision on whether you should remove or treat. If you decide to preserve your trees you will need to learn which treatment is best for your tree.

Down load a PDF version of this symptoms cheatsheet

Call your Arborist!


Emerald Ash Borer Treatment and Control

Fortunately Colorado has the advantage of learning from the trials and errors of the states that have already faced this dilemma. There are many treatments that have been used to try and control this pest but only a few have proven effective. Larger Ash trees, approximately 10 inches or greater in dbh, are effectively protected by TREE-Age, emamectin benzoate. I am recommending this as the only treatment for large trees as some eastern companies have had close to 100% effectiveness when applied properly. Additionally it lasts for 2 years. Smaller trees, 10inches> in dbh may be treated with a soil drench using an imidacloprid. Products are available for homeowners to apply imidacloprid themselves however some are not labeled to for two applications per year which is necessary for some formula concentrations to be effective.

For more information visit:

EAB Insecticide Fact Sheet.pdf
Insecticide Trunk Injection Treatments in Green Ash

Planning Ahead

Trees that are already infested or stressed have less chance of being saved. The EAB has avoided detection through pheromone traps so far. We are not certain if it is in our area but there is a high probability we will see it soon if it is not already present.

The best proactive measures tree owners can take are to have an Arborist survey their trees and prescribe treatments. There may be alternate suggestions for treatments from different tree companies. Be certain that you are getting emamectin benzoate applied to your large trees. If your planning on treating smaller trees yourself, ask an arborist for the best products available on the market and for the best methods for application. Applications should be made around April/May depending on the weather.

Other useful links:

Purdue University EAB Study
Slow Ash Mortality Pilot Project