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Emerald Ash Borer FAQ

Amended from the multinational Emerald Ash Borer website -

The natural range of emerald ash borer (Agrilus planipennis) is eastern Russia, northern China, Japan, and Korea.

EAB was first detected in southeast Michigan in 2002. While it is not exactly certain on its mode of arrival, it most likely came in ash wood used for stabilizing cargo in ships or for packing or crating heavy consumer products. It was first detected in Tennessee in July 2010 at a truck stop in west Knox County off of I-40 near the Loudon County line.

In North America, it has only been found in ash trees. All sizes and even very healthy ash trees can be killed. All of Tennessee's native ash trees (green, white, blue and pumpkin ash), as well as many horticultural cultivars (cultivated varieties of ash or hybrids between species of ash), are susceptible to EAB infestation.

Since its discovery in southeastern Michigan in 2002, the Emerald Ash Borer (EAB) beetle has been found in Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, Virginia, West Virginia and Wisconsin. As of July 2010, it is now found in Knox County, Tennessee.

The canopy of infested trees begins to thin above infested portions of the trunk and major branches because the borer destroys the water and nutrient conducting tissues under the bark. Heavily infested trees exhibit canopy die-back usually starting at the top of the tree. One-third to one-half of the branches may die in one year. Most of the canopy will be dead within 2 years of when symptoms are first observed. Sometimes ash trees push out sprouts from the trunk after the upper portions of the tree dies. Although difficult to see, the adult beetles leave a "D"-shaped exit hole in the bark, roughly 1/8 inch in diameter, when they emerge in June.

The adult beetle is dark metallic green in color, 1/2 inch-long and 1/8 inch wide. There are several pictures of EAB in the Photo Album and EAB Life Cycle pages.

Recent research shows that the beetle can have a one- or two-year life cycle. Adults begin emerging in mid to late May with peak emergence in late June. Females usually begin laying eggs about 2 weeks after emergence. Eggs hatch in 1-2 weeks, and the tiny larvae bore through the bark and into the cambium - the area between the bark and wood where nutrient levels are high. The larvae feed under the bark for several weeks, usually from late July or early August through October. The larvae typically pass through four stages, eventually reaching a size of roughly 1 to 1.25 inches long. Most EAB larvae overwinter in a small chamber in the outer bark or in the outer inch of wood. Pupation occurs in spring and the new generation of adults will emerge in May or early June, to begin the cycle again. View the EAB life cycle.

Adult EAB can fly at least 1/2 mile from the tree, but generally do not fly far from where they emerge. Many infestations, however, were started when people moved infested ash nursery trees, logs, or firewood into uninfested areas. Shipments of ash nursery trees and ash logs with bark are now regulated, and transporting firewood outside of the quarantined areas is illegal, but transport of infested firewood remains a problem. PLEASE - do not move any ash firewood or logs outside of the quarantined area.

No one knows for sure, but experts feel that it may have been in the Detroit area for at least 15 years. The initial infestation probably started from a small number of beetles. Over the next few years, the population began to build and spread. By 2002, many trees in southeastern Michigan were dead or dying. In North America, native ash trees have little or no resistance to EAB and natural enemies have so far had little effect when EAB populations are high.

Healthy ash trees are also susceptible, although beetles may prefer to lay eggs or feed on stressed trees. When EAB populations are high, small trees may die within 1-2 years of becoming infested and large trees can be killed in 3-4 years.

There is a national effort to limit the spread and impact of EAB. A national plan, coordinated by the U.S. Department of Agriculture, Animal Plant Health Inspection Service (APHIS), guides what federal, state and local officials must do to manage this insect. Infested areas are quarantined, which means that selected materials such as firewood from deciduous trees, ash nursery stock, and ash logs may not be moved out of infested areas. Where outlying infestations are detected, large numbers of infested ash trees are sometimes cut and destroyed to reduce EAB populations. Research is underway in many universities and government agencies to find better ways to detect and manage this pest.

  • EAB is becoming an international problem, with infestations in Canada and the United States. The scope of this problem could reach the billions of dollars nationwide if not dealt with. State and federal agencies have made this problem a priority. Homeowners can also help by carefully monitoring their ash trees for signs and symptoms of EAB throughout the year.
  • In Tennessee, an estimated 261 million ash trees on timberland could potentially become infested with EAB. This represents a potential value loss of over $9 billion (USDA Forest Service).
  • Timber uses: major export commodity used in furniture, cabinets, flooring, caskets, tool handles, sports equipment (e.g. baseball bats, hockey sticks, canoe paddles), mineland reclamation.
  • 127 mills throughout the state report using and processing ash logs (TDF).
  • Another 10 million ash trees in urban areas are potentially at risk with a value loss of another $2 billion. (TN Forest Resource Assessment and Strategy (in review)).
  • Uses: street/shade/beautification tree widely planted in urban areas due to its fast growth, beautiful fall color, ease of maintenance, and hardiness to urban environment.
  • Wildlife uses: seeds of ash are eaten by several species of birds. The bark is occasionally food for rabbits, beaver and porcupine. Cavity excavating and nesting birds often use ash.

Keeping trees vigorous and healthy by proper pruning, mulching, watering and avoiding wounding helps them resist insect attacks. No insecticides are 100% effective against emerald ash borer attacks. Not bringing firewood from other states is one of the best ways to avoid bringing home unwanted tree pests.

At this time, you need not change your scheduled timber management activities.

Yes, scientists have observed parasitic wasps attacking egg or larval stages of the emerald ash borer in its native land. Efforts are underway to determine if these wasps could be safe and effective controls of EAB in America. Unfortunately, this process is time-consuming and these wasps may not be available for effective use in current EAB containment efforts. Other studies are testing various fungi and bacteria that infect beetles for possible use as "natural insecticides."

In general, having a diversity of tree species in your yard, on your street or in your community is your best defense against all tree health problems. Plant no more than 10 percent of any one tree species in your yard. Because of the severe nature of the EAB threat, the wisest choice at this time is not to plant any ash trees.

Currently, EAB is regulated for in Knox and Loudon Counties. The following are regulated articles and are restricted from movement: EAB itself, firewood of all hardwood (non-coniferous) species; nursery stock, green lumber, and other material living, dead, cut, or fallen, including logs, stumps, roots, branches, mulch and composted and un-composted chips of the genus Fraxinus. Any other article, product, or means of conveyance not listed above may be designated as a regulated article if the commissioner determines that it presents a risk of spreading Emerald Ash Borer and notifies the person in possession of the article, product, or means of conveyance that it is subject to these regulations.

Educate yourself on how to recognize signs and symptoms of EAB and share this information with your neighbors.

Contact Tennessee Department of Agriculture through the interactive form. Be sure to complete the form in its entirety to ensure prompt response.