Emerald Ash Borers: A Guide For Your Landscape Trees

Ash trees in North America are in danger of dying out completely due to the invasive emerald ash borer. The following guide can help you recognize and prevent infestations so your trees remain healthy.


Although adult ash borers will feed on the leaves of ash trees, this damage isn't what devastates the plants. Instead, ash trees die due to the damages caused by ash borer larvae. Ash borers lay their eggs just beneath the bark of an ash tree. The larvae then hatch and burrow into the wood to feed and mature, later burrowing out of the trunk to begin the cycle again. A severe infestation will decimate the the tree and cause irreparable harm, which then causes the ash to decline and die.


The beetles themselves are easy to spot. They are a brightly colored metallic green, with adult beetles measuring about a half inch in length. The adults are often found in the foliage feeding or crawling on the trunk of the tree looking for egg-laying sites. Larvae are rarely seen since they burrow in the tree. Sometimes you may spot one if bark flakes from the tree. The larva are worm-like and cream colored with a brown head and ten body segments.


Symptoms of these pests are more obvious the larger the infestation becomes. Some of the earliest symptoms appear in the canopy. You may notice that the canopy appears thinner with fewer leaves. Often, the leave loss begins at the top of the canopy and gradually worsens until the gaps caused by dropping leaves become obvious. As an infestation worsens, bark damage becomes more obvious. You will notice splitting bark on the trunk, along 1/8 inch long holes that are shaped like the letter "D." If the bark flakes off, there will be zig-zagging tunnels on the surface of the trunk just beneath the bark.


The best treatment is prevention. If you have ash trees on your property and there has been emerald ash borer infestations in your area, then schedule a preemptive treatment. The most effective of these treatments are those applied to the soil, called a soil drench, or those injected into the trunk. There are also bark and canopy sprays, but these don't always work as well as soil drenches and trunk injections. If a tree is already infested with borers, these treatments may be effective in the early stages of the infestation, but often removal of the tree is the only option for more severe infestations.

Contact a tree service to learn more about emerald ash borer treatments in your area.