As far as insects go, it’s not unattractive — it could even be considered beautiful, especially if you’re a bug fancier. One could imagine an amateur entomologist gleefully photographing the bullet-shaped adult with its metallic, iridescent green wings, or a middle school science student proudly pinning it to a board alongside butterflies and rhinoceros beetles. But make no mistake: emerald ash borer (Agrilus planipennis), is a “pretty poison,” more foe than friend.
Emerald ash borer, or EAB, is an Asian native first documented in the U.S. in 2002 near Detroit, Michigan. It had traveled here, tucked cozily away in wooden shipping pallets or other packing materials.
Once here, researchers believe that the transport of firewood became its primary mode of travel within the country. In Asia, its population is kept in check by several native wasp species. Much of EAB’s success in North America is because these natural enemies are missing.
EAB feeds on all species of ash trees (Fraxinus spp.), and that’s a big deal. In woodlands, ashes are prized hardwoods that yield end products such as cabinetry, molding and baseball bats.
In urban settings, ashes may comprise as much as 40 percent of the canopy in parks and neighborhoods. Many may remember those American elms that lined city streets before Dutch elm disease came along in the ’50s and ’60s? Many locales replaced their beloved elms with ashes after that.
For anyone familiar with wood-boring beetles, EAB’s life cycle is typical. The female lays her eggs between layers of outer bark and in cracks and crevices of the trunk and major branches during the summer. About two weeks later, depending on the weather, the larvae hatch and bore through the bark, feeding on the cambial tissue for several weeks.
The tunnels they make eventually gird the tree, cutting off its ability to take up moisture and nutrients, which leads to its death within two to three years. The developing larvae pass through four developmental stages before emerging as adults the following year, leaving D-shaped exit holes approximately 3 millimeters wide in the trunk. Adventitious basal shoots, vertical bark splits and woodpecker activity are further hints that EAB is at play.
Unlike some other borers that tend to go for trees weakened by drought or disease, EAB will hit healthy trees almost as quickly as sickened ones.
EAB is gaining ground, having already killed hundreds of millions of ash trees in the U.S. and Canada. Despite quarantines led by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service and well-coordinated public information campaigns regarding the transport of firewood, the Emerald Ash Borer Information Network reports that this invasive pest is now active in 35 states and five Canadian provinces since its initial discovery in Michigan.
For the green industry, as well as for research and educational entities, EAB is a heartbreaking addition to the growing list of invasive insects that are impacting forests and urban landscapes alike. Unfortunately, there is no magic bullet for EAB’s eradication. Some of the tiny wasps that feed on it have been released here, but it will take decades before they build up enough numbers to have an impact.
The key to success in combating this invasive pest is to avoid working in a vacuum. Green industry professionals should make it a point to coordinate their management and outreach efforts with others in the industry, as well as stay connected with land-grant universities and government entities involved in the fight. Furthermore, it’s imperative that companies help their customers navigate meaningful solutions.
“I was actually the one who discovered EAB in the metro area back in 2015,” says Brandt Jelken, an arborist at Perficut in Des Moines, Iowa. “But long before that, our company saw the emerging threat and purchased the necessary equipment to deal with it.”
Jelken stresses the necessity of using tools in the most efficient way possible, and that goes beyond just reading the product label. “We worked closely with our chemical supplier to ensure that, not only were we offering the best product on the market, we were applying it correctly,” he says.
Companies that haven’t previously offered plant health care as a service may see an opportunity to expand their repertoires once customers demand a response to EAB, but it should never be as simple as just grabbing the first product you see and applying it. Local and regional variables, such as microclimates, are always at play.
Four active ingredients are being used systemically against EAB at the moment: imidacloprid, dinotefuran, azadirachtin and emamectin benzoate. Depending on the formulation, application methods include soil drench, trunk injection or systemic bark spray. In addition, permethrin, bifenthrin, cyfluthrin and carbaryl may have value as a preventative cover spray for smaller specimen trees.
It would benefit the landscape or tree care professional to build a relationship with his or her suppliers to determine which products and application methods make the most sense in a given situation from an ecological and an economic perspective.
Membership in professional associations can prove invaluable when faced with something like EAB. Through them, you can network with other companies and find out what they’re doing and how successful their efforts have been, especially those that are located in regions where EAB has been active for much longer.
Relationships with clientele
Customers can be hesitant to grasp this truth, but saving every ash isn’t realistic. Especially within regions where EAB is a newer challenge, companies are scrambling to find the best approach. An initial step is to help clients prioritize. William de Vos, a consulting arborist and owner of TreeWorks Ltd. in Montpelier, Vermont, has chosen to be proactive, speaking to groups about the pest. During those presentations, he recommends a simple starting point: take inventory.
The inventory questions should include: How many ash trees does the customer have? How large are they? Logistically, will some be easier to treat than others? Are certain trees more valuable than others due to personal attachment, or do they function as urban amenities?
An inventory can get the ball rolling and encourage a client to begin looking at his or her ashes analytically. Plus, it’s an action step — something a property owner and a green industry professional can do now, well in advance of an infestation. According to the North Central Integrated Pest Management Center, it’s probably too soon to begin preventative treatments if the beetles’ known presence is greater than 10 to 15 miles away. But it’s not too soon to conduct an inventory and start making plans.
The next step de Vos advises is “to be patient and wait until spring — after the leaves appear but before the adults emerge. Then soon thereafter, have them evaluated professionally for structural, physiological and aesthetic health.”
All this input — from both the client and the professional — will serve as the basis for a treatment regime, if and when the pest creeps closer than that 15-mile buffer. The specific approach will depend on a list of variables, especially cost.
The treatment route that de Vos prefers to determine if trees are significant and healthy enough to warrant the cost is a trunk injection of Tree-age G4 (emamectin benzoate) applied via a canister infusion or Arbojet’s QUIK-jet AIR injector system.
“My approach has always been to recommend removal and replacement,” says Jelken. “I’ve consulted for city councils, homeowner associations and private homeowners, and the message has always been the same. Unless your ash tree has historical significance or sentimental value, you should give strong consideration to cutting it down.”
Jelken explains that since treatment is based on trunk diameter, preventative insecticidal treatments will continue to get more and more costly for the tree’s owner as will the eventual cost of removal.
“Long story short, EAB is going to cost us one way or another — either by trying to save the trees with treatments or by removing and replacing them,” says Jelken. “Ultimately, it is up to the stakeholders to decide which is a better use for their dollars. And as often as not, it’s not an easy decision.”
For those green industry professionals who don’t already work with university cooperative extension personnel within their service areas, such contacts can prove invaluable. Local extension offices serve as clearinghouses for information on EAB detections, quarantines and treatment options.
“Extension educators are enthusiastic about sharing their knowledge,” says Dr. Elizabeth Barnes, an exotic forest pest educator with Purdue University, West Lafayette, Indiana. “Often, due to their close contact with researchers, they have information not yet available to the general public. They also love talking to industry professionals because it gives them an idea of the issues and programs that their areas need the most.”
Management recommendations change to keep up with shifting situations. Barnes says, “In places like Indiana that have already been hard hit by emerald ash borer, management research has had to expand to include best management practices for dealing with dangerous and brittle dead ash trees.” She adds, by checking in regularly with extension agents, green industry pros can get this kind of information as soon as it’s released and straight from the source.
A familiarity with the science behind a treatment option can produce added confidence that in turn creates value for the customer. De Vos explains how a researcher recently told him about particular product he was using with an efficacy of up to four years.
“I still recommend going by the manufacturer’s label, which advises reapplying every two years,” he says, “but I suggest that they may be okay treating every three years if the cost of treatment is a burden for them. I place clients on a list to be notified every two years, regardless of their treatment choices.”
He does admit, “All this being said, I am relatively new at EAB treatment and have not yet seen the efficacy of my work, but I am optimistic.”
When it’s all said and done, optimism could be the green industry’s greatest weapon against the EAB threat.
Phillip Meeks is an educator in the areas of natural resources, agriculture and horticulture. He resides in the mountains of southwest Virginia and can be reached at firstname.lastname@example.org.
LEARN MORE: Discover if EAB has been detected in your state at www.emeraldashborer.info. The site also has updates and educational resources like EAB University, which provides webinar-based information and research on these costly and destructive pests.