Emerald Ash Borer (EAB) is an Asian beetle, first detected in Michigan in 2002. It has since killed tens of millions of ash trees in southeastern Michigan alone, with tens of millions more lost in Illinois, Indiana, Kentucky, Minnesota, Missouri, New York, Ohio, Ontario, Pennsylvania, Quebec, Virginia, West Virginia, and Wisconsin.
In addition to spreading by natural means, EAB can be transported to new areas in infested firewood, timber, and nursery stock. States and provinces have enacted intense quarantines against moving wood, but it has still cost municipalities, property owners, nursery operators and forest products industries tens of millions of dollars. The challenge before us is to reduce the loss of remaining elms and to choose suitable replacement trees for the ones we cannot save.
In North America, EAB is known to infest all species of ash (Fraxinus spp.). Ash can be recognized by the presence of compound leaves which are arranged opposite of one another on the branches.
Eggs are laid between layers of bark and in bark crevices. Larvae hatch in about one week and bore into the tree where they feed on the inner bark and phloem, creating “S”-shaped galleries. Larvae go through four feeding stages, and then excavate a pupal chamber in the fall, where they will overwinter as prepupae. Pupation occurs in late spring, and adults begin to emerge through “D”-shaped exit holes in May and early June. Adults will remain active until the end of summer.
A commonly encountered beetle, the six spotted green tiger beetle, Cicindela sexguttata, is often mistaken for EAB due to its similar appearance. It is a predator of small insects and is frequently found on hiking trails. There are other insects often mistaken for EAB as well.
Symptoms and Signs
New infestations are difficult to detect, as damage to the tree may not be apparent for up to three years. Symptoms of an infestation can include branch dieback in the upper crown, excessive epicormic branching on the tree trunk, and vertical bark splits. Woodpecker damage is sometimes apparent.
Courtesy of: USDA Forest Service Northeastern Area State and Private Forestry; NA-PR-05-04; (Revised August 2009)