Emerald Ash Borer (EAB)
The Emerald Ash Borer (Agrilus Planipennis), or EAB, is an invasive wood-boring insect that has been the cause of widespread Ash tree (Fraxinus spp.) decline and mortality in North America. Thought to be originally introduced through shipping containers from international ports, further distribution was due to transporting infested ash nursery stock, unprocessed logs, firewood, and other ash commodities. Federal and state quarantines in infested states now regulate transport of these produces, however unfortunately, the pest has continued to spread to previously unaffected areas of the Unites States, including Virginia.
How does EAB kill trees? EAB attacks only true ash trees, including the green and white ash that are prevalent in Virginia. They target trees of all ages and sizes, and can be a severe blow to even more established trees, greatly weaken them and making them more susceptible to other infestations and diseases. EAB also feeds on ash trees in their native range in Asia, however those trees, having co-evolved along side with the beetles, have developed natural defenses to them - our native ash trees have not.
EAB begins to destroy ash trees by laying eggs between the crevices of the bark. Once the eggs hatch, the larvae will bore into the tree by chewing through the bark, and feeding on the phloem and cambium layers of the tree, which interrupts the flow of nutrients and water. After overwintering in the tree, the metallic green-blue bodied EAB adults (approximately 1/2-inch in length) will emerge in the spring, leaving small, 1/8-inch, diameter D-shape exit holes. From there, they fly off to other nearby ash trees and begin the cycle again. This cycle greatly stresses the ash trees, causing thinning leaves, die-back in the tree’s canopy, bark loss, and eventually, death to the trees.
Local Programs and Projects
In an effort to combat the loss of our local ash trees, different management methods and tree treatments have been explored by various groups in Richmond.
The James River Park System (JRPS) Invasive Species Task Force, in partnership with the Richmond Tree Stewards, have been treating ash trees in the City of Richmond’s parks system. The City’s Urban Forestry Division has started exploring partnerships with local companies for the treatment of street trees, and the state’s Department of Forestry has offered cost sharing programs, to help offset the cost of treatment for residents with ash trees on their private properties.
Treating on a preventative basis, before symptoms are present, is most effective. Common symptoms to look out for can be thinning or yellowing of the canopy, bark "blonding" due to woodpeckers scratching in search of larvae, D-shaped exit holes along the branches and trunk, splits in the bark exposing callused tissue and S-shaped larval feeding galleries, etc.
Several types of insecticides have been shown to be effective in controlling EAB. These may be applied to soil, injected into the tree's trunk, or sprayed on the trunk by a VDACS-certified pesticide applicator. Currently, the most effective method is trunk injection of an emamectin benzoate product every 2-4 years. An annual soil drench of a high concentration dinotefuran or imidacloprid product is the second-most effective treatment method.
Note: this pesticide cannot be applied near water bodies or flowering plants and is ineffective at controlling high populations of EAB.
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