Emerald Ash Borer (EAB)

First of all, this is not intended to be an all-encompassing sheet on EAB. The best research-based, University information is available and kept current at www.emeraldashborer.info.

EAB is a small, leaf-eating beetle, that feeds and causes damage to ash trees, but this isn’t where they do their damage.
The damage comes from the larvae. The larvae feeds, just below the bark in the vascular area of the tree. This feeding disrupts the transfer of water and nutrients to the leaves, first causing thinning and eventually death. Emergence holes are a distinctive “D-shape”.

The first symptom you will see is a thinning at the top of the tree, then the damage will appear further down,  then you may start to see those emergence holes, down lower. Unlike other borers that only affect larger trees under some type of stress, these borers go after all ash trees, young and old trees alike and whether healthy or not.

Some things to consider: The information says not to treat until EAB are found within 15 miles of where they have been found. I say, look at the progression, it has NOT been leaps of 15 miles, but pockets of movement. Ask the tree owner “How important is that tree to you?” If it is important and they understand they will have to treat, EVERY YEAR, then I would start treatment this year. By the time they find them in your area, it may be too late.

The people of Boulder CO thought they were safe for a long time, then they were found there. The far bottom image is an Ash Mortality Rate chart, it starts out slow but eventually, 100% of untreated trees die, treat or remove.


Treatment for homeowners is basically limited to, ferti-lome Tree & Shrub Systemic Insect Drench. This easy to use product requires a bucket with one gallon of water. Then measure around the trunk of the tree, waist to chest high . Take your measurement,  and put one ounce of Drench per inch, into the bucket of water. (in this case 29 ounces). Pull mulch away from the trunk and pour the mixture at the very base of the tree. Do not apply 3 feet away, it will NOT be effective! Let it soak in, push the mulch back and water in.

The website says NOT to apply after June, and for control of EAB that is correct, but it is still effective on other insects. To get them started, make an application now, then get on the rotation of applying every Spring. Summer applications have variable effectiveness due to limited transpiration in the tree, but if the tree is important, I would start making applications immediately.