The emerald ash borer (Agrilus planipennis) is an invasive, wood-boring beetle. The adult beetles nibble on ash foliage but cause little damage. The larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients.

The emerald ash borer (EAB) probably arrived in the United States on solid wood packing material originating in its native Asia. Since its discovery in 2002 in Michigan, the EAB has killed hundreds of millions of ash trees from Colorado and the Midwest to New England and south to Georgia. It has caused regulatory agencies and the USDA to enforce quarantines to prevent potentially infested ash trees or wood from spreading EAB, and it has cost municipalities, property owners, nursery operators and forest products industries hundreds of millions of dollars.

Ash makes up about 4% to 15% of Connecticut’s forests and represents about 2% to 3% of the urban trees in many communities. A tree that has been attacked by EAB can die within two to four years.   

How to identify an ash tree


The four identifying features of ash trees include:

  • An opposite branching pattern (two branches come off the main stem, one on each side and directly opposite each other);

  • Compound leaves composed of seven to 11 leaflets depending on the species of ash;

  • Smooth twigs that are rigid and grayish in color;

  • Deeply furrowed bark on mature trees.


The white ash is a large tree, commonly 70 to 80 feet in height. Its wood is heavy, hard, strong and elastic and used for furniture, agricultural implements, tool handles, baseball bats, railway ties and fuel.

Visible signs of EAB infestation include:


  • Visible decline or dieback of the upper canopy in spring and summer.

  • Heavy woodpecker damage on ash trees may be a sign of infestation.   Woodpeckers flake off the outermost bark exposing the defined S-shaped galleries made by the larvae as it feeds on the cambien just under the bark.

  • D-shaped exit holes appear in the tree trunk — the EAB is in the larvae stage for most of the year until in the spring when it chews its way out and emerges as an adult in May.

  • Epicormic sprouts — the damaged ash tree sends out new spouts at the base of the tree to protect itself by making new leaves.  

  • Chewed leaves, the adult EAB


What you can do


For removing large trees call your local licensed arborist. If you are removing trees yourself consider using the wood for the fireplace or wood stove. Ash wood is an excellent fuel source. Do not transport ash wood out of town. Connecticut has a moratorium on moving firewood to help slow the spread of this serious pest. If your newly dead trees are not near a structure consider leaving the lower 10 to 20 feet as a “standing snag,” this provides a great habitat enhancement providing nesting, shelter and food for a wide range of our wild neighbors.

Replant different species of hardwood trees. Call Mike Conklin, Wilton’s director of Environmental Affairs at 203-563-0182 for recommendations on what to plant as a replacement.

Claire Rutledge, Ph.D., associate agricultural scientist at the Connecticut Agricultural Experiment Station is scheduled to talk Sept. 19, 7 p.m., in the Wilton Library’s Brubeck Room about the history and biology of the emerald ash borer in North America in general, and Connecticut in particular. Among the topics that will be discussed are the beetles’ host range, detection techniques and term management strategies.