DEEP: Emerald Ash Borer (EAB)

Emerald Ash Borer (EAB)

Help Slow the Spread of the Emerald Ash Borer
Emerald Ash Borer has been found in Connecticut.
Currently there is a quarantine on the movement of
ash materials and firewood out of the State of Connecticut.
Page Content
Self Issued Certificate for Transportation of Firewood :   On-line Form  | Word FormPDF
{adult emerald ash borer}
Unless otherwise indicated, photos are courtesy of Forestry Images
The emerald ash borer (EAB) is now known to be in Connecticut.  EAB was first found in the state during the week of July 16, 2012.  Previously, this invasive and damaging insect was not known to be in Connecticut, although it had been found in nearby parts of New York State.    
DEEP, the CT Agricultural Experiment Station (CAES), USDA APHIS PPQ and the US Forest Service, working together with local partners, are taking prompt action both to define the extent of this infestation and to limit its spread beyond where the insect is already known to be.  This will be a long-term effort on the part of all involved.
 Property owners concerned about a specific ash tree should consider what steps they might take to protect their tree.  Generally, one should not treat an ash tree until one knows that EAB has been found within 10-15 miles of that tree.  Very good information on caring for ash trees can be found at
Forestland owners should also give careful thought to the management of their woodlands in the face of EAB.  The most important recommendation is to not act hastily.  There are excellent resources available, including within the forestry program at DEEP.  A range of options should be considered before committing to the removal of ash trees or other trees due to this new insect pest. 
DEEP and CAES will continue to provide direction and updates regarding the emerald ash borer as more becomes known about the extent and intensity of the infestation.
People in Connecticut are increasingly aware of the very real threat that invasive, exotic insects pose to the trees and forests of the state.  Over the past century, the state's native woodlands and its urban forests have been hard hit by the gypsy moth, the Japanese beetle and the hemlock woolly adelgid, among other pests.  More recently, the state has been bracing for the possibility that the Asian longhorned beetle will be found within its borders.  In the meantime, another invasive insect has arrived - the emerald ash borer.
  {eab with wings spread} {metallic looking eab}
The emerald ash borer is a small, green beetle that belongs to a large family of beetles known as the buprestids, or metallic wood boring beetles.  The description is apt, as many of the adult buprestids are indeed glossy, appearing as if their wing covers are made of polished metal.  The emerald ash borer, with its green, iridescent wing covers, fits right in.  Adult EABs are between 0.3 to 0.55 inches in length - small by most standards but large compared to other buprestids - and relatively slender.
{emerald ash borer lifecycle}
During its life cycle, EAB undergoes a complete metamorphosis.  It starts as an egg, becomes a larva (alternatively called a grub), and then changes to become a pupa and then an adult.  The life cycle of an EAB takes either 1 or 2 years to complete.  Adults begin emerging from within ash trees around the middle of June, with emergence continuing for about 5 weeks.  The female starts laying her eggs on the bark of ash trees about 2 weeks after emergence.  After 7 to 10 days, the eggs hatch and the larvae move into the bark, to begin feeding on the phloem (inner bark) and cambium of the tree.  Throughout each of its successive instars (larval growth stages), the larva continues to feed within this same part of the tree.  The larval stage may last for nearly two years.  Before becoming an adult, the insect overwinters as a pre-pupal larva.  It then pupates in the spring and emerges as an adult during the summer.
  {EAB larva}
EAB feeds strictly on ash trees.  The larvae feed on the phloem and cambium, while the adults feed on leaves.  In Connecticut, there are three species of ash trees - the white ash (Fraxinus americana), the green or red ash (F. pennsylvanica) and the black ash (F. nigra ).   Despite its common name, mountain ash (Sorbus spp.) is not a true ash and does not attract the EAB.  (Learn how to identify an ash tree.)

  {bronze birch borer}
Bronze Birch Borer, with exit hole
  {two lined chestnut borer}
Two Lined Chestnut Borer
Two other buprestids are well-known to those in Connecticut who are concerned about trees.  The bronze birch borer is a pest of ornamental birch trees.  The two-lined chestnut borer often attacks stressed oak trees, including oaks in the forest.
EAB is an insect that is not native to North America.  It was first found in 2002 in the vicinity of Detroit, MI and Windsor, ON.  It had arrived sometime within the several years previous, presumably on woody packaging materials.   It is now known to be found in 22 states.  It is considered to be established in several of the upper Midwest states where it was first found.  Movement of ash, in particular ash nursery stock and ash wood in the form of firewood, logs and wood packaging materials, has been cited as a likely means by which EAB has been assisted in its spread.  More recently, strict regulations have been initiated to prevent the movement of these materials from infested areas. 
{damage from the EAB}  
Photo by Dr. Victoria Smith, CT Agricultural Experiment Station
Because the larval EAB feeds on the phloem and cambium of the tree, and because its numbers in an area tend to build up rapidly, infestation by EAB usually leads to the death of trees that are infested, often within 2-3 years.  Phloem tissue is part of the inner bark of the tree.  It is that part of the tree that carries the sugars produced by the leaves throughout the rest of the tree, including down to the roots.  As the EAB feeds on the phloem, other parts of the tree become cut off from their food source.  This effectively girdles the tree and it dies.  The cambial tissue, found between the bark and wood of a tree, is that part of the tree that generates new xylem (wood) and phloem tissue.  Because of that, EAB also curtails the ability of the tree to respond to the injury it is inflicting.
Most boring insects preferentially attack stressed or injured trees, as healthy trees are able to resist these insects through such means as the production of inhibiting chemicals.  Native North American ash species have not evolved in the presence of EAB and so are not equipped to deal with this problem.   Thus, even healthy native ash trees do not have the ability to effectively resist the onslaught of this invasive, exotic beetle.  
{ash distribution in CT}
Dark green areas are forested with up to a 19% ash component,
light green areas have an ash component of less than 5%. 
By number of stems, ash trees make up just slightly less than 3% of the trees in the Connecticut forest.  Most ash trees in Connecticut are white ash.  Ash in Connecticut have already been seriously declining for several decades due, at least in part, to a disease called ash yellows.  One concern is that EAB might severely reduce the population level of ash in the state to a point where it may not be able to recover.
{badly damaged ash tree in NY State}
Photo by Kevin Grady, CT DEEP Division of Forestry
The loss of ash trees from the forest, like the loss of any specific kind of tree, would lead to rippling effects on other organisms living in the woods.  Butterflies and moths from nearly 30 different families live on ash trees.  Seeds of ash are eaten by wood duck, bob white, purple finch, pine grosbeak and fox squirrels.  According to the US Forest Service, the elm/ash/red maple forest type is the third most common forest type in the state.  While not all stands of this forest type contain ash, it is considered to be a common component.  Foresters report that, where ash has been lost in stands in which it had been common, undesirable invasive plants are often quick to fill the gap.
The wood of the white ash is prized due to its combination of strength and flexibility.  Uses such as shovel handles and baseball bats take advantage of these properties, while other uses, such as in electric guitar bodies, take advantage of its workability.  Stumpage price reports demonstrate the consistent role that this wood plays in Connecticut's timber markets, even if the value of ash logs in Connecticut does not tend to be high.
Ash is also a minor component of the urban forest.  In the northeast, green ash is not the staple street tree that it is in other parts of the country, but it is regularly used to add diversity to the urban forests throughout the state.
The first symptom that an ash tree is infested with EAB is often thinning and dieback in the tree's upper canopy.  This is as a result of EAB infesting the top of a tree first.  However, there can be many causes for thinning and dieback in the crown of an ash tree, so that symptom alone should not be seen as diagnostic.
  {d-shaped exit hole}
{emerging adult eab}
A definite sign of the EAB is the presence of a D shaped exit hole in the bark of an ash tree.  This is the hole left by the emerging adult following pupation, as it chews its way out of the tree.   While there are several other borers that attack ash, none of them produce that same-shaped exit hole.  Other buprestids, such as the bronze birch borer and the two-lined chestnut borer, do produce D shaped exit holes, but these insects are not found on ash trees.  The combination of a D shaped exit hole and an ash tree is unique to EAB, and a sure indication that the insect is present.
  {epicormic sprouts from EAB damage}
Photo by Dr. Victoria Smith, CT Agricultural Experiment Station
However, such exit holes can be very difficult to see.  Searchers looking to find EAB should also look for other indications of its presence.  When ash trees are seriously infested, oftentimes the entire upper crown of the tree will be dead.  At the same time, in an effort to survive, these trees may be sending up numerous shoots from the lower part of the trunk or the root flare.  In heavily infested trees, one may cut out a flap of bark to reveal the characteristic s-shaped tunnels of the burrowing larvae.  With so many larvae active in the tree, woodpeckers will also likely be boring holes in the bark or stripping bark off in patches as they search for EAB grubs to feed on.  The signs of woodpecker activity on ash trees may be the most tell-tale when it comes to finding EAB.
  {trap tree being felled}   {purple }
 A girdled 'trap tree' being felled 
photo by Chris Donnelly
Purple 'Barney trap' in ash tree 
photo courtesy USDA
  {cerceris wasp}
Cerceris fumipennis with prey (not an EAB) 
photo courtesy of
Aside from direct observations, there are three main techniques being used to find EAB.  These are:
  • trap trees
  • purple traps
  • biosurveillance
Trap trees are existing ash trees that are girdled - that have a strip of bark cut out in a band around the trunk of the tree - so that the tree becomes highly stressed.  The stressed trees send out chemical signals that draw in boring insects generally to feed on and breed in the weakened tree.  After several months, these traps trees are cut down and thoroughly inspected for the presence of EAB.
The purple traps, often called 'Barney traps' because of their size and color, attract EAB due to their color.  They also contain a chemical attractant.  These traps are sticky.  Any insects that land on the trap, including an EAB, will become stuck.  These traps are regularly monitored for any EAB that they might have caught.
"Biosurveillance" is the third way of searching for EAB.  This method takes advantage of the fact that a native, solitary, non-stinging wasp, Cerceris fumipennis, hunts for buprestids of all types and brings them back to their nesting hole to provide food for their young.  "Wasp watchers" catch the wasp as it returns to its nest and take its prey from it, to determine if the wasps are bringing any EAB back from its foraging.
It should be noted that none of these methods will draw EAB into an area where it is not already present.  The use of traps will not cause an area to become infested.
In 2012, Connecticut became the 16th state known to have EAB within its borders.  Because EAB is already considered as established in certain parts of North America, eradication of the insect is no longer the goal.  Instead, focus is on slowing or preventing the spread of the insect into new areas while managing and reducing its numbers in places where it is already found. 
Efforts to slow EAB's spread can have very real, positive benefits.  This approach buys time until a more effective response to the insect can be found.  Investigations continue into forestry techniques, biological control and methods of chemical control.  At the same time, there is the potential that natural controls may emerge.  Examples of potential natural controls include a genetic response on the part of ash trees or the emergence of already occurring diseases or predators that can provide a check on EAB.
This stands in sharp contrast to the approach being used for the Asian longhorned beetle (ALB).  In that case, eradication of the insect in North America is the goal.  Due to the behavior of ALB, the potential for eradication is very good, and so the effort is aggressive.  The interest in controlling EAB is just as strong, but, with eradication no longer considered as being realistic, Connecticut's response emphasizes slowing the spread, through: 
  • A quarantine to keep any infested ash materials from leaving Connecticut.  Specifically, ash logs, hardwood firewood, yard waste and ash nursery stock are all focus of concerns.  Details of the quarantine will be announced by CAES.
  • A ban on the importation of firewood into Connecticut through New York or Massachusetts - unless it is properly certified that it has not come from an area already infested.
  • A partnership with USDA APHIS and the US Forest Service to determine how long the EAB infestation has been present in Connecticut.  This information will help determine the best strategies to be used to limit its spread.

For people in the State of Connecticut, the three most important ways in which an individual can help in this effort is:
  1. Be aware of the possibility of the presence of this insect in Connecticut, including becoming familiar with the signs of its presence on ash trees;
  2. Report any suspected finds to the CT Agricultural Experiment Station, and;
  3. Be especially careful when moving any firewood or young trees. 
Using firewood that is obtained locally, near to where it will be used, and not moving firewood great distances, are very important in the effort to prevent further spread of the EAB.
To report a possible EAB find, call the Experiment Station at 203-974-8474 or the following email address: Please do not move either the insect or wood from the site where you think the insect might be.  It is much better to take a digital photo and email it to the email address above.  Also, give a precise description of the location of the tree so that an investigator from the Station will be able to visit the site.
All emails and calls regarding potential finds will be appreciated.  Investigators would much prefer to record a negative find than to have missed out on an early discovery of the beetle in the state.
EAB Cost Calculator Presentation (presented at the 2014 CT Conference on Natural Resources)
(learn about the purple traps)
Content last updated on December 5, 2014