How to Tell if a Tree is Infected by the Emerald Ash Borer?

The emerald ash borer was first discovered in 2002, although the insect had taken up residence in the trees several years prior. Since that time, it has spread throughout eastern Canada and the United States, killing more than 50 million trees and endangering billions more. An emerald ash borer Ontario infestation is something any ash tree owner should be alert to.

Insect Life Cycle

Female ash borers lay their eggs underneath the bark of ash trees. When the larvae hatch, they feed on the wood of the trunk, cutting off the flow of nutrients to the tree in the process. If the infestation goes unchecked, the tree will eventually die. However, it may be possible to save an infected tree with injections of insecticide. This is most effective if the infestation is identified early.

Signs of an infestation can be difficult to recognize. They often occur high up in the tree at first, they can mimic the symptoms of other tree health issues, and they may not show up until after the infestation has advanced significantly. The following are among the most troubling signs of emerald ash borer infestation. If you notice any of these signs in the trees on your property, you should contact a professional tree service right away.

Tree Signs

Epicormic shoots are new green growths that extend from the roots or the trunk of an infested tree or sometimes from large branches. The shoots are known by several colloquial names, such as witches’ brooms, water sprouts, or suckers. They are signs that the tree is under stress. Trees infested with emerald ash borer gradually produce fewer leaves, and the leaves they do produce tend to be smaller and more yellow. They quickly wilt and fall off the tree, leaving bare branches behind.

If you look at the trunk of your tree and see the bark splitting or cracking, this may be a sign of EAB infestation. The splits may be as short as five centimeters in length or as long as 15. The bark around the split may become discolored, turning brown or pinkish, particularly if the tree is young.

Branch fractures tend to occur more often in trees infested with EAB. Branches tend to break near the point that they extend from the trunk. Nevertheless, this can be difficult to observe from the ground because the fractures first occur in the branches of the upper canopy.

Insect Signs

Branch fractures and bark splits may reveal larval galleries. These are the tunnels that the EAB larvae leave behind them as they eat through the wood. They form a characteristic serpentine or “zig-zag” pattern. Larvae of other insects also leave behind galleries, but usually in more random patterns.

Once the EAB larvae grow to maturity, they make holes in the bark by which to exit the tree. These are only a few millimeters wide and have a distinctive D-shape. Holes left by other insects may appear D-shaped at first, but removing the bark reveals them to be round or oval in shape. EAB exit holes maintain the D-shape even when the bark is removed.

The new adults are hungry when they first exit the tree and start feeding on the leaves. You may notice the notches they cut along the sides of the leaves. You may also notice stripping of the bark or holes surrounded by light-colored patches. These are caused by animals trying to eat the larvae, such as squirrels or woodpeckers.

Dealing With Emerald Ash Borer Ontario

Treatment with insecticide must take place every two years for at least 10 years. This is usually a more cost-effective option than removing the tree. Only a professional should treat an ash tree with insecticide. Find out more about Emerald Ash Borer prevention from Martin’s Tree Service and contact us for an estimate.