Last updated: September 13, 2022
Article
Monitoring for Emerald Ash Borer in Acadia National Park
Image courtesy of Abbe Museum Digital Archive
By Sophia Cameron, Invasive Plant Management Intern and Jesse Wheeler, Vegetation Program Manager
What is Emerald Ash Borer?
The emerald ash borer (Agrilus planipennis Fairemaire) is a shiny, green beetle originating from Asia. Though they are visually pleasing to look at, they have caused some of the greatest destruction to North American forests in history. The emerald ash borer (EAB) infestation is predicted to cause upwards of $10.7 billion worth of damages to native ash trees (Fraxinus sp.) of North America, and irreplaceable cultural loss to many indigenous communities. The brown ash in particular is referred to as Basket Tree by Wabanaki Tribes, due to its unique bark structure that allows for the creation of sturdy and beautiful woven works of art. Attached to this practice is also a very spiritual connection to the ash tree.
EAB was detected in Michigan, as well as across the U.S. border in Ontario, Canada, in 2002. Since then, it has moved to infect 35 more states in the U.S. and other locations in Canada, becoming one of the five most common invasive animals in National Parks. It is predicted to continue to spread throughout the U.S., though national management plans are in place to hopefully limit future infestations.
Photo courtesy of Leah Bauer, USDA
Effects to Ash Populations
EAB feed on the phloem (vasculature layer) of all species of ash tree in the areas that they have been detected. Once the phloem is damaged, the trees can no longer move water and other nutrients throughout their trunks, and they eventually die, usually within 3-5 years.
It is currently believed that all species of ash trees in North America can be affected by EAB including black (brown), green, white, and blue ash species. A majority of studies conducted in the U.S. have found almost complete mortality of infected ash trees, meaning that it cannot be effectively treated. Because of this, prevention of the spread of EAB has been the primary method of control.
Lifecycle of Emerald Ash Borer
Adult insects can live for approximately three to six weeks, and feed on the leaves of the ash trees. After mating, the adult females lay eggs in the crevices of the bark of the tree, which take about two weeks to hatch. The larvae then “bore” through the bark and into the phloem layer, which is where their name comes from. They continue to feed and grow through the fall and winter and emerge as adults around late spring.
Although the emerald ash borer resembles other beetles, such as the bronze birch borer, and the six-spotted tiger beetle, it is unique in that it only infests ash (Fraxinus) species. Six-spotted tiger beetles are ground beetles that are very bright metallic green but are larger than EAB and have a distinctively different, more rounded body shape.
- Size: ½” body length
- Color: Adults have metallic green wing covers and purple to coppery red abdomens.
Image courtesy of MEDACF, Maine Forest Service
What Can We Do?
Unfortunately, it can often be very difficult to detect early infestations when it may be treatable, since the eggs are usually laid in the upper parts of the trees, above eye level. Because of this, the most effective strategy of management has been to prevent the spread through quarantines and education. Ash products that may be infected are quarantined and tested nationally before being moved anywhere outside of their state of origin. People shouldn’t move firewood long distances, burn it where you buy it.
Property owners are also being urged to remove any ash trees that they believe to be infected, to prevent further spread within their state. Another proposed alternative is to use biological controls for EAB, or to use predators or parasites of the beetle to eliminate it. One example of this is the mass rearing and release of a species of parasitic wasp that lays their eggs on the larvae of EAB.
What to Look For
- Adult beetles emerge May–September
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Leafy offshoots from the lower trunk of ash trees (epicormic branching)
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Severe woodpecker activity; “blonding” effect with outer bark plucked off
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Dead top branches of ash trees
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S-shaped tunnels throughout inner bark
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D-shaped exit holes 1/8” wide on bark surface
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Emerald Ash Borer beetles spread only about ½ mile on its own in a year but could be moved hundreds of miles in one day within a piece of infested firewood.
NPS
Monitoring in Acadia
EAB was detected in Aroostook and York Counties of Maine in 2018. However, it has not yet been found in National Park units in the state, including Acadia National Park, Katahdin Woods and Waters National Monument, and Saint Croix Island National Historic Site. Acadia and adjacent landowners are monitoring for EAB using girdled trap trees, a tool used to detect this highly invasive forest insect pest. The bark is stripped off an ash tree in a long band around the tree, cutting off the flow of nutrients and water between the crown and roots. Girdling stresses the tree and causes it to emit chemicals that attract adult EAB in the area. The beetles then lay their eggs among the furrows of the bark. Once the eggs hatch, the larvae bury into the tree and begin to feed on the inner bark (cambium) layers, leaving sinuous trails of excavated wood. We can take the tree down and peel the bark away, looking for these larval galleries as evidence of its presence in the area.
Visitors and property owners within the state are urged to report suspected infestations or sightings (https://www.maine.gov/dacf/php/caps/EAB/EABreportFORM.shtml) to state entomologists and park officials if observed near Acadia. Campers at Acadia campgrounds are also prohibited to transport their own firewood, to prevent the accidental introduction of EAB to our ash population.
Additional Information
Emerald Ash Borer Information Network
http://www.emeraldashborer.info/
www.maine.gov/firewood
Acadia Invasive Insects and Diseases
References
Herms, Daniel A., and Deborah G. McCullough. 2014. “Emerald Ash Borer Invasion of North America: History, Biology, Ecology, Impacts, and Management.” Annual Review of Entomology 59 (1): 13–30. https://doi.org/10.1146/annurev-ento-011613-162051.
Kovacs, Kent F., Robert G. Haight, Deborah G. McCullough, Rodrigo J. Mercader, Nathan W. Siegert, and Andrew M. Liebhold. 2010. “Cost of Potential Emerald Ash Borer Damage in U.S. Communities, 2009–2019.” Ecological Economics 69 (3): 569–78. https://doi.org/10.1016/j.ecolecon.2009.09.004.
Poland, Therese M., and Deborah G. McCullough. 2006. “Emerald Ash Borer: Invasion of the Urban Forest and the Threat to North America’s Ash Resource.” Journal of Forestry 104 (3): 118–24. https://doi.org/10.1093/jof/104.3.118.