EAB in Denver – FAQ

By now, many Colorado residents are familiar with the name emerald ash borer (more commonly known as EAB). In fact, it’s now considered one of the most destructive forest pests ever seen in North America.

Ash trees make up approximately 15-20% of Colorado’s urban forest. It’s no longer a question of IF emerald ash borer will spread to the Denver Metro area, but WHEN.

Swingle Lawn, Tree & Landscape Care recently turned to its Senior Consulting Arborist, Steven Geist, to answer some frequently asked questions about treating and protecting against EAB in Denver.

EAB in Denver – FAQ

How effective are insecticide treatments against Emerald Ash Borer?
Under experimental conditions, most results indicate a 90 percent or higher success rate.  In practical applications, success rates for insecticide treatments are at least 80 percent effective.  Why the difference?   Trees treated early, and in good vigor, have the highest success rate.

The insecticides used to combat EAB are nearly all systemic.  That means the insecticide is placed in the soil or injected directly into the trunk of the tree.  The insecticide is taken up into the tree via the vascular system.  Emerald ash borer and other ash borers feed in that vascular system as well.  When the insects have compromised the vascular system, the insecticide is not able to disperse evenly throughout the tree.

In addition to treating for EAB, trees should also be pruned while following other good horticultural practices emphasizing tree health.

Will I have to treat my ash tree forever?
The answer is yes and no.

Emerald ash borer infestations follow a definite curve.  For the first 3 years, EAB goes undetected while it’s infesting trees.  During the next 2 to 3 years, borer populations build.  During this “cusp” period, preventive treatments are recommended.  For the next 10 years, the borer goes through an exponential growth phase.

Treatments for EAB are essential.  The result: most of the treated trees live, while nearly all the untreated trees die.  With few trees left for EAB to infest, the populations of EAB will decline rapidly.  Researchers in the mid-west are now looking at this post mortality phase.  It looks as if treatments may be scaled back after this period.

If I treat my tree what should I expect? 

If the tree is not treated it will die, that is a known fact.  Some have asked, “If I treat my tree, will it look the same as it does now?” Maybe…and maybe not.

While the success rate for insecticide treatment is very high, when emerald ash borer becomes prolific, they will challenge the tree – or begin feeding on the tree before the insecticide controls them.   Thus ash trees, even when treated, will accumulate more dead branches than normal and have a more sparse appearance to the tree canopy.   When the EAB mortality curve subsides, the ash should return to its normal vigor.

So what does that mean for you? Sooner than later, if you have an ash tree, you need to plan ahead especially if you are in the Denver metro area. Waiting to treat until AFTER EAB in Denver is discovered on your property or an adjacent property is NOT a good strategy.

In an effort to help treat and combat this destructive forest pest, Swingle is offering Complimentary ash tree evaluations on commercial and residential properties across the Front Range. Call today to help control the spread of EAB – 303-337-6200.