Protect Your Trees: Emerald Ash Borer

The emerald ash borer (agrilus planipennis fairmaire) is an invasive insect native to Asia. The Emerald Ash Borers (EAB) attacks all species of ash trees, and EAB has already been linked to the deaths of tens of millions of ash trees in the Eastern and Midwestern US.

EAB begins with adult beetles laying eggs on the bark of ash trees. When the eggs hatch, the larvae bore into the bark and feed on the tissues of the tree. This disrupts the movement of nutrients and water within the tree, girdling it and causing tree death. Adult beetles are metallic green in color, and leave a D-shape exit hole in the bark when they emerge in the spring. EAB larva are creamy white in color and have flattened, bell-shaped body segments.

Do Your Trees Have EAB?

Some characteristics that are present with EAB include, canopy dieback that begins on the top third of the tree and progress until the tree is bare; epicormic shoots (sprouts growing from the trunk and roots of the tree); bark splitting with vertical fissures on the bark; and larval feeding galleries that are usually in a serpentine shape.

Another possible sign that EAB may be attacking your trees is the presence of woodpeckers. Woodpeckers feed on the EAB larva, and peck the outer bark while foraging for food.

Preventing and Treating EAB

If possible, it’s best to use preventative measures to keep your trees safe from infestation. By the time most people notice canopy thinning or dieback, EAB has already caused considerable damage to the vascular system of the tree. Peak egg hatch and larval establishment occur between early June and mid-August, depending on location and weather. As a general rule, young larvae are more susceptible to insecticides than older larvae.

Insecticides that can effectively control EAB fall into four categories: (1) systemic insecticides that are applied as soil injections or drenches; (2) systemic insecticides applied as trunk injections; (3) systemic insecticides applied as lower trunk sprays; and (4) protective cover sprays that are applied to the trunk, main branches, and foliage. Evergreen Arborists can advise on which treatments would be best to prevent or treat EAB.

It’s important to note that while an effective insecticide may stop additional damage, it cannot reverse damage that has already occurred from EAB. It takes time for trees to recover. Since most insecticides treatments for EAB control act systemically, the insecticide must be transported within the tree. This means that the tree must be healthy enough to carry the insecticide through the trunk and into the branches and canopy.

Multi-year studies have shown that if more than 50% of the canopy has been killed by EAB or if the canopy appears to be thin, it is probably too late to save the tree. The ability of trees to recover from low to moderate EAB injury can vary, depending on the extent of the damage and which control options are used.

Is the Emerald Ash Borer in Your Area?

Quarantine maps for the EAB can be found on the www.emeraldashborer.info website. Although, once an infestation has been noted in the area, surveys by regulatory officials end. Similarly, once an entire state is declared to be infested, regulatory surveys may cease. Therefore, quarantine maps may or may not adequately reflect the current distribution of EAB in such areas.

Evergreen Arborists are available to discuss prevention and treatment of EAB. With warmer weather just around the corner, now is the best time to give us a call.