Emerald Ash Borer Information
The Emerald Ash Borer is a pest native to Asia that came to the United States through wooden packing material. It was first discovered in Michigan in 2002 and found in New Jersey in 2014. It has no natural predators in the United States and has killed over 40 million ash trees throughout the US as of 2015. It is estimated that over $20 billion in total losses will occur throughout the country. The insect is less than a half inch in length and can be identified by its bright green outer shell and reddish copper upper abdomen.
Adults are active from May to August where they eat on the leaves of ash trees and mate. Females lay eggs in bark crevices during this time which hatch within 7-10 days. Larvae emerge and chew through the bark where they feed on the cambium of the tree. The cambium is the living tissue of the tree, consisting of the xylem and phloem, which transports water and nutrients throughout the tree. The larvae eat this sapwood area and create serpentine looking galleries until autumn. Larvae then overwinter and emerge in May as adults through newly made exit holes.
Signs and Symptoms
Emerald Ash Borer adults have a unique D-shaped exit hole that gives the best indication that the pest is attacking a tree. However, the minute size of these holes combined with the fact that the beetles prefer the heat from the sun and generally attack the upper portion of a tree makes them extremely difficult to detect. Dieback in the upper canopy is another, more easily detectable sign of infestation. A tree can exhibit 30-50% loss of canopy within the first 1-2 years of infection, and total death within 3-4 years, thus early detection and treatment is key to saving a tree. Increased woodpecker activity is also a sign of larvae in a tree, as well as evidence of serpentine larval galleries under loose bark.
The Value of Trees
Size, health, and location are all important in evaluating the value of a tree. Trees also contribute to health benefits, increased property values, and the quality of life within a neighborhood. Studies have shown that a reduction in the urban forest also leads to an increase in respiratory and cardiovascular deaths within a given area. These factors all contribute to the overall value of saving a tree compared to the expense of proper pruning, treatment applications, or the cost of removal and replacement.
Within a given municipality where the presence of ash trees is abundant, community action and support is a necessity. Education about the threat of EAB and value of trees on both public and private land needs to be done. Marking ash trees at risk of death with visible tags is a good way to illustrate the extent of the damage that can occur. Creating and maintaining an inventory of public and street trees, including location, size, and species, is a great way to begin a management plan. An ideal plan calls for the preservation and treatment of valuable and specimen trees, while instituting the removal of potentially hazardous trees, both preemptively and after death. The value of a tree should be calculated, including the benefits a tree provides for air pollution reduction, storm water run off, and temperature regulation and compared to the loss value of a given tree. The National Tree Benefits Calculator helps estimate and compare the costs of different management responses, including treatment, removal, and replacement for varying size ranges.
Initial control regulations called for the complete removal of all ash trees within a given area. This caused an increased spread of EAB as the reduction in the number of host trees led to an increased rate of travel of the pest. Chemical control and conservation can be a viable and economical management strategy especially when the significant environmental and economic benefits of established trees are considered. Proper treatment can maintain a functional and aesthetically pleasing tree canopy and should be done once the Emerald Ash Borer is detected within 10-15 miles of a given property. Insecticides can effectively and consistently protect even large trees under intense pest pressure, but need to be applied when trees are still relatively healthy or before an infestation begins. Unfortunately, by the time dieback is usually noticed, considerable damage to the trees vascular system has already occurred. Insecticides may stop additional damage, but cannot reverse any existing damage. In declining trees, they may continue to deteriorate the first year and improve the second year if the treatment proves to be successful. If 50% or more of the canopy has thinned or died, treatment is not recommended. Insecticides act systemically and trees need to be healthy enough to transport the chemical through its vascular system. Since larval feeding galleries injure the xylem and phloem tissue that are used to transport water and nutrients, the transportation ability of a tree is impaired. Drought stress further inhibits the uptake and transportation of systemics and supplemental irrigation may be needed during periods of drought.
Insecticide Options and Recommendations
Insecticides can be applied in four ways. Due to the cost benefit and effectiveness, a trunk injection of ememectin benzoate (Tree-age) is the most recommended treatment method.
- Trunk Injection – Can be done to trees of all sizes whenever the trees have leaves and are transpiring. It is the fastest way for a tree to absorb a chemical and is done through tiny injection sites at the base of a tree. Tree-age is the most economical and effective systemic used and is done through a bi-annual treatment. TreeAzin (Azadirachtin) is another chemical type, but is shown to be slightly less effective and may need to be applied annually in high density EAB areas. This insecticide acts differently than all others as it is not lethal to the insect, but does remove them from treated trees. Imicide (Imidacloprid) may also be applied as an annual treatment to small trees.
- Soil Injection – Recommended for smaller trees (under 15”-20”) as an annual treatment. This method is applied through a chemical drench injected into the soil around a tree and must be done under adequate soil conditions. Imidacloprid is the most common chemical used, usually under the name brand Merit or Zylam, but Dinotefuran (Safari, Transect, or Xytect) may also be used. It must be applied in the early spring, or by an increased dosage in the fall.
- Trunk Spray – A low pressure spray applied to the lower 5-6’ of the tree trunk that penetrates through the bark and into the vascular system of a tree. It has the second fastest absorption rate, must be done annually, and carries the same effectiveness as a soil injection. Dinotefuran is the only chemical type to do this and is sold under the trade name Safari, Transect, or Xytect.
- Cover Sprays – A variety of cover sprays may be sprayed directly onto the trunk, limbs, and leaves of a tree to kill any active adults present at the time of application. 1-2 applications per year are needed, but it does not protect the tree from any new pest attacks. This method also has a high probability of chemical drift, and is the least recommended preventative. It is not a systemic and is rarely used to treat for EAB.
Why Hire An Arborist?
Adequate prevention and maintenance begins with hiring a qualified arborist. Make sure the person and company you trust has the proper knowledge and training. Companies should be members of the Tree Care Industry Association (TCIA), and individual representatives should be ISA Certified Arborists and New Jersey Certified Tree Experts (CTE). There are other accreditations that a company can claim to have, so be sure to check credentials. A company should also have the proper insurances to protect you and their workers, and have a Certified Pesticide Applicators License.
Additional information can be found at www.EmeraldAshBorer.info.
EAB research is constantly changing and updating, and the information provided is current as of 2015.