Emerald Ash Borer: The Emerald Ash Borer (EAB) is an introduced beetle, originally from southeast Asia. Since its discovery in North America in 2002, and it has spread throughout much of the northeast and mid-Atlantic U.S., where it has caused widespread destruction. All species of ash trees (Fraxinus spp.) are susceptible, and nearly all infected die, typically within about 4 years. Recently, the EAB has spread into forests of Virginia, and was discovered in Radford / Montgomery County, VA, in 2016.
Emerald Ash Borer spends most of its life on ash trees. EAB adults feed on canopy leaves and lay eggs under the bark of ash trees. However, most tree damage results from the emerging beetle larvae. These grubs tunnel through the inner bark and feed on the phloem (tree sap), girdling and killing the ash trees (see photo to right). Larvae eventually mature into winged adults, These emerald green adult beetles burrow their way out of the tree through characteristic "D-shaped exit holes". (See photos below). Woodpecker activity is often visible on infected trees, as the birds remove the bark to feed heavily on EAB larvae. See the Southern Forest Health website for an overview and references on the Emerald Ash Borer. At Wildwood Park, the Emerald Ash Borer was first discovered by Radford University-Forest & Wetland Ecology (BIOL 476) students as they conduct field research for this project. EAB damage was found on numerous white ash trees (Fraxinus americana) in Dry-Mesic Oak Forests on the west-facing slope of Wildwood Park. Find out more about introduction, impacts, and potential control methods for the Emerald Ash Borer in eastern North America in this video. |
Damage to white ash from the Emerald Ash Borer, a recently introduced insect pest in Virginia forests. Photo from Wildwood Park, taken by Radford University Forest and Wetland Ecology class.
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Adults of the Emerald Ash Borer are small, emerald green beetles, on average about a half inch long and a sixteenth of an inch wide (photo below). The adult EAB beetle burrows out of the bark, leaving characteristic "exit holes" shaped like a D in the bark. (photo to right). The number of exit holes on the tree bark is an indicator of a tree's level of infestation. As the infestation progresses, the tree is under increasing stress and often will loose its leaves prematurely. As larva, the EAB is a white worm that is flattened with a pair of brown pincher-like appendages. The larva is what does the damage and kills the ash trees, not the mature adult beetles.The larva leave trails in the bark where they burrowed through it, the appearance of these burrows is another indicator the tree is infested. Since the discovery of the EAB, it has killed over 50 million ash trees in North America (Knight et al., 2013). |
Tree defoliation has been a big problem with the Emerald Ash Borer. At Wildwood Park, we noticed many of the trees were losing their canopy and most of their bark. The EAB (beetle) burrow into the bark of the tree and lay their eggs. They can have up to hundreds of larvae and as these larvae burrow through the tree they affect how the tree absorbs nutrients. The loss of the bark tends to start at the top of the tree and works its way down. Many woodpeckers hunt the larvae and also contribute to destroying the bark. Once trees are infected by the larvae, the tree’s life is shortened dramatically. Many of the trees die within 4 to 6 years (Knight et al., 2013)
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The hemlock wooly adelgid has devastated hemlock populations in Central and Southern Appalachian forests. The pest is killed by cold temperatures and is thus less destructive in the northern Appalachians. However, temperatures here in the Central and Southern Appalachian region do not stay cold enough to limit the pest, contributing to its rapid spread in the region.
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