What You Can do About Emerald Ash Borer

Although emerald ash borer is smaller than a penny, it has already caused millions of dollars in damage to ash trees. (Photo courtesy of Howard Russell, MSU, Bugwood.org)

When I lived in St. Louis, I had a mature ash tree in my back yard.  It was so beautiful that in the winter, I would sometimes go outside on a moonlit night just to admire the tree’s magnificent form.

I often wonder whether that tree is still standing, now that emerald ash borer (EAB) has spread through 22 states and killed millions of ash trees in less than 12 years.

Since 2002, EAB has been steadily advancing westward from Michigan, culminating most recently in the discovery of the borer in Boulder County, Colorado.  Although EAB wasn’t spotted in that county until September 2013, research indicates that the borers had been at work for three or four years.  According to Colorado State University Extension, it’s anticipated that nearly all of northeastern Colorado will be infested within the next decade.

The city of Boulder alone has 98,000 ash trees; metro Denver has nearly 1.5 million.  You may have several ashes on your block or even in your yard.  So you can imagine the threat that the loss of these trees represents.

If you’re not sure whether your trees are ashes, you can visit the Colorado Department of Agriculture’s EAB page and click the Is your tree an ash tree? link under Additional Resources to see photos and descriptions of ashes.  The EAB page contains an accessible collection of information and resources concerning the emerald ash borer.

What can you do to slow the spread of EAB and handle its consequences?  Here are several suggestions.

• Don’t transport firewood.  EAB’s flight range is about five miles.  If you carry firewood or other ash materials containing live borers to other locations, you’ll extend EAB’s reach exponentially.  Try to buy firewood where you camp.
• Keep your ash trees healthy.  This means watering, fertilizing and pruning these plants appropriately.  Colorado State University Extension offers free online tree-care publications, such as Caring for Trees in a Dry Climate.  If your ash trees are healthy, they stand a better chance of absorbing systemic insecticides when treated.
• 

  Beneath the tree’s bark, emerald ash borers create S-shaped tunnels that prevent water and nutrients from flowing throughout the tree. (Photo courtesy of Eric R. Day, VA Polytechnic Institute & State U., Bugwood.org)

  Educate yourself about the signs of EAB, which include a thinning canopy, suckering from the tree roots, epicormic branching (weird shoots often sprouting from dormant buds on the trunk), tiny D-shaped exit holes, and S-shaped tunnels under the bark.  Just click the EAB Identification and Reporting link on the EAB page mentioned earlier.  If you suspect that your ash has EAB, contact the Colorado Department of Agriculture by phone at 888-248-5535 or by email at CAPS.program@state.co.us.

• Monitor EAB’s spread on the EAB page.  If you own ash trees and there’s an infestation within five miles of your neighborhood, you’ll need to decide whether your ashes are worth the money, time and effort involved in EAB control.
• Explore treatment options.  Colorado State University entomology professor Whitney Cranshaw has developed a helpful publication on control options, including specific insecticides and application procedures, which you’ll also find on the EAB page.
• Promote tree diversity.  If you plant a variety of tree species on your property, you’ll be less vulnerable to threats to specific tree types, such as ash or Dutch elm.  For a list of suitable trees for the Front Range, click this Colorado Nursery Growers Association link.  Also, be aware that Denver Botanic Gardens and the University of Denver are co-sponsoring a tree diversity conference at the University of Denver on March 7.  For information, visit the University of Denver website.