Thursday, July 29, 2021

Emerald Ash Borer and Ash Trees – A New Approach

The emerald ash borer adult is a green buprestid or jewel beetle about 1/2 inch long.

The emerald ash borer (EAB) is a half-inch long, green buprestid or jewel beetle. It’s an invasive insect native to Asia, believed to have made its way to the United States on solid wood packing material carried in cargo ships or on airplanes.

Emerald Ash Borer was first discovered in the United States in 2002, near Detroit, Michigan. Around that time, it was also found across the Detroit River in Windsor, Ontario, Canada. In 2003, the United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) initiated a domestic quarantine program for areas infested with the extremely destructive wood-boring pest of ash trees, but the insect still managed to progressively advance and expand its range.

EAB is now present in 35 states, the District of Columbia, and 5 Canadian provinces and is responsible for the destruction of hundreds of millions of ash trees in forests, rural areas, and urban and suburban landscapes. It has become the most destructive and costly invasive forest insect in North America.

States in the eastern U.S. produce nearly 114 million board feet of ash saw-timber annually, with a value of more than $25 billion. The compensatory value of the 8 billion ash trees on U.S. federal, state, and private forest land potentially infested with EAB is estimated to be $282 billion.

Emerald ash borer adults chew D-shaped emergence holes to exit from ash trees. Photo credit: Debbie Miller USDA Forest Service;

Emerald Ash Borer in New York State 

Emerald Ash Borer was first discovered in New York State in the spring of 2009, after two USDA Agricultural Research Service employees recognized damage to ash trees in the Town of Randolph, in Cattaraugus County. The infestation was reported by Rick Hoebeke, a Senior Cornell Cooperative Extension (CCE) Associate who served as the Assistant Curator of the Cornell University Insect Collection from 1977-2011. The presence of EAB has now been confirmed in all New York counties except Essex, Hamilton, Lewis, and Washington. New York State Department of Environmental Conservation (DEC) continues to work with CCE to detect and confirm new infestations across the state.

Most EAB infestations are started by unknowingly moving infested firewood, nursery trees, or saw logs. So, in an effort to limit the potential introduction of the beetle into other areas of the state, DEC initiated regulations which placed infested counties under quarantine and initiated eradication activities in quarantined areas. The quarantines restricted the movement of ash trees, ash products, and all species of firewood.

Regulations Have Changed 

While DEC continues to collect new EAB location information, they are no longer actively managing EAB infestations. This course of action evidently stems from a December 2020 APHIS ruling removing all federal domestic EAB quarantine regulations. DEC’s mandate restricting the movement of firewood of any tree species to within 50 miles of its source or origin remains in effect however, and ‘Best Management Practices’ recommendations for moving ash logs have been established. If you must move ash wood that is not firewood, please learn more about and be sure to follow DEC guidelines. New York has more than 900 million ash trees, representing about seven or eight percent of the trees in the state. And all are at risk.

The oobius agrili parasitic wasp is extremely small and doesn't have a stinger It lays its eggs within emerald ash borer eggs, killing the host egg Photo Credit - Houping Liu MicLegions of Parasitoid Wasp are Being Raised and Released 

In preference to regulating containment, APHIS has been redirecting its focus toward what researchers have determined will be a more effective, more sustainable, and less intrusive long-term method for EAB management. Biological control (bio-control) is the practice of importing and releasing natural enemies from a pest’s native range to help manage the target-pest’s populations in areas of introduction. APHIS research into natural enemies of EAB has identified several species of small, female parasitoid wasps that don’t bite or sting, but which seeks out EAB, in order to lay their eggs inside the bodies of living EAB larvae. When the wasp eggs hatch, the developing wasp larvae feed on their living hosts; ultimately killing them. One extremely tiny species of wasp lays its eggs within the eggs of the beetle, killing the host egg.

To date, APHIS, along with numerous state, county, tribal, and academic partnering agencies, has released more than 8 million of the parasitoid wasps in 30 states and the District of Columbia. Offspring have been recovered in 22 states, indicating that the wasps are successfully establishing, reproducing, and killing EAB. APHIS rears the wasps at a facility in Michigan and ships them to their partners, who then release the parasitic bio-control agents into areas where EAB is infesting ash trees. Because this strategy focuses directly on the ash boring insect, it’s widely acknowledged as a very promising course of action for reducing EAB populations and protecting North American ash trees.

A female parasitoid wasp laying its eggs into a larval ash borer host. Photo Credit - David Cappaert;

In 2013, the U.S. Forest Service began providing wasps to the Canadian government. Natural Resources Canada is now productively rearing wasps at a laboratory in Sault Ste. Marie, Ontario, for use in their own EAB bio-control program.

USDA’s bio-control goal is to stabilize and eventually reduce EAB populations by initially releasing the parasitoid wasps into every county with a known EAB population large enough to sustain the wasps and then expanding the distribution and increasing the number of wasps released in EAB-infested states. Wasps have already been released in several New York counties; including Clinton, St. Lawrence, and Jefferson counties, in the North Country. Whether the introduced parasitoids can regulate EAB populations at low enough densities to facilitate long-term survival of ash regeneration remains to be seen.


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Richard Gast is a retired Extension Program Educator and has been contracted by Cornell Cooperative Extension Franklin County to continue his informative and thought provoking articles.

7 Responses

  1. nathan says:

    parasitic wasps from outside the USA being released, so in 10 years we will be hearing about how these wasps are destroying how many native species??? Good luck, as almost every time these attempts back fire!

  2. Vanessa B says:

    Unfortunately for much of the mid Atlantic it’s too late. My parents cut down all of their dead ash trees a few years ago. Hopefully this other insect will help, but EAB is a tough customer. 🙁

  3. Dan says:

    It doesn’t take a lengthy visit to Essex, NY to confirm EAB is in that County. I reported ash borer populations on the Hamilton/Franklin county
    border multiple times to a USDA Forest Service eab hotline back in 2013. Yet the first “occurence”(as labeled in an Almanack article recently) just began last year in the Adirondacks. The whole thing is sad. Who gets to decide to release additional varieties of foreign species into our environment? Is it okay for me to breed and release non native species if I want to experiment with outcomes?
    If anyone has any black ash trees they would like to see turned into baskets or windsor chairs, feel free to reach me by email. Also interested in any variety of ash tree that has grown with its trunk in a pronounced J shape.

    • Dan says:

      Also the image of the EAB looking out of a D shaped exit hole toward the top of the article is someone’s computer edited creation and probably should not be used in journalism pieces.

  4. Worth Gretter says:

    Richard, your article is very informative but there is a problem with the numbers in one place:

    “States in the eastern U.S. produce nearly 114 million board feet of ash saw-timber annually, with a value of more than $25 billion.”
    That works out to $219 per board foot, but ash lumber is selling for less than $10 per board foot.

    The next sentence is probably good:
    “The compensatory value of the 8 billion ash trees on U.S. federal, state, and private forest land potentially infested with EAB is estimated to be $282 billion.”
    That would be $35 per tree, which might be the value of the tree before any effort is made to harvest and process it.

  5. upstater says:

    Thank you for a most informative article, Richard. Unfortunately the biological controls are too late in Central New York. We have acres of dead ash on our 23 acre property. It is costing us over $10,000 to have a land clearing outfit take down hundreds ash trees. The large diameter trees are cut with a chainsaw and they use a forestry mulcher on a skidsteer to grind the tops and small diameter trees. Without the clearing, we’d lose access to most of our property on our trails. Not the kind of economic stimulus we need!

    Cheap autoparts from China… Privatized profits and socialized losses.

    Elms, Beech, Ash, what next?

    • Boreas says:

      Am. Chestnut loss to invasive blight was arguably our biggest loss to date. Not only was it great wood, the nuts provided both food and reliable income for those willing to simply pick them up – not to mention the impact on wildlife.

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