Emerald Ash Borer

Agrilus planipennis

Key Features

  • Thinned canopy
  • Woodpecker holes, bark splits
  • Zig-zag patterns etched under bark
Canopy thinning and shoot sprouting from EAB
Bark chips and trunk with bark removed by woodpeckers. Photo by T. Luck
Bark Splitting from EAB


Early symptoms of ash or fringe tree are present on the upper third of the tree. This includes a thinned canopy, presence of woodpecker holes, or splits in the bark that reveal curvy zig-zag galleries beneath. As tree health declines, fewer branches will be healthy enough to sprout leaves. Many trees will begin to sprout shoots from the sides of branches and trunks in a desperate attempt to grow. Woodpeckers searching for larvae beneath the bark can chip off strips of bark that can accumulate at the base of an infested tree. Adult beetles are bright metallic green and difficult to see when they are in the tree canopy feeding on leaves. Adults have rounded bellies and flat backs and are small enough to fit on a penny. Their peculiar shape accounts for the distinctive "D"-shaped exit holes from which they emerge from trees. The bark of heavily infested trees can come off in sheets, revealing the distinctive galleries left by the white larvae that feed beneath the surface. Larvae are recognized by their bell shaped segments and their flattened shape.

Bark holes from woodpeckers feeding on EAB
Sprouting shoots near base of tree from EAB
Zig-zag patterns etched by larvae of emerald ash borer


Adults emerge from tree trunk to feed on leaves in late spring when black locust blooms. Females lay eggs on bark after feeding for a few weeks. Larvae damage trees by consuming vascular tissue beneath the bark. This destroys the ability of the tree to take water and nutrients from tree roots to the leaves, killing a tree in 1-3 years. In late summer, mature larvae dig about 1/2 inch below the bark surface to turn into pupae, the transition phase between larvae and adult beetles. Larvae and pupae overwinter beneath the bark until the weather warms in spring when adults emerge. There is only one generation per year.

D-shaped emergence hole
Emerald ash borer adult
Emerald ash borer larvae

Management Recommendations

It is usually less expensive to save a healthy ash tree than to remove it from an urban landscape. Canopy thinning is the best way to assess tree health. Be sure to refer to photos in the damage section to get a feel for different levels of thinning. If 50% of the canopy is gone, the tree is not healthy enough to treat. Consult a plant health professional before treating and injured tree to be sure that the remaining live portion of the tree is worth saving. Systemic insecticides in the spring can protect trees that receive adequate irrigation. Pollinators are not harmed by applications of insecticides directed against EAB. Emamectin benzoate can be injected by a professional to protect trees that have lost up to 50% of their canopy and lasts for up to 3 years. Azadiractin (TreeAzin) can be used successfully by professionals if injected annually before canopy has been lost. Other products can applied by homeowners each spring that will protect trees with a trunk diameter 4.5 ft above the ground of 12 inches or less provided there is no more than 30% canopy thinning. Products containing imidacloprid with or without clothianidin are readily available in home garden centers. Products containing dinotefuran and less widely available. Fertilization does not improve the capacity of a product to protect a tree. Visit the useful links section for more detailed information about managing emerald ash borer in Indiana, videos of how to apply product, what to expect when a professional injects your tree, how to report your find to local authorities and how to plant a tree.

Effective Pesticides

Active Ingredients include: Azadirachtin, Clothianidin, Dinotefuran, Emamectin Benzoate, Imidacloprid

landscape report
Purdue Landscape Report
Plant & Pest Diagnostic Laboratory