Emerald Ash Borer

emerald ash borer
Agrilus planipennis

In the summer of 2002, scientists realized that widespread damage to ash (Fraxinus) in southern Michigan was caused by an introduced insect, the emerald ash borer (Agrilus planipennis) (Federal Register, October 14, 2003, Volume 68, Number 198). The pest is thought to have been established in Michigan for at least 10 years by the time of its discovery (Siegert 2006). By the time the beetle was detected in Michigan and adjacent Ontario, it had already infested a large area. Since then it has spread further. By the beginning of 2010, the known infestation affected more than 100,000 square miles in 12 states (Lucik pers. comm. January 2010).  By mid-2012, outbreaks had been detected in 16 states- and in mid 2015, that same number was up to 25 states and 2 Canadian provinces.  Outbreaks continue to be found at sites hundreds of miles from the nearest known location – indicating that infested wood continues to be illegally moved.

Outbreaks and infestations of emerald ash borer are announced very frequently. To find the most current information on locations and status of each state, province, and county, it is best to go to Emeraldashborer.info or access their current map, typically updated once a month. Canadian provinces are also included on this location map, with confirmed infestations now ranging from Manitoba to New Brunswick.

USFS scientists and managers developed a conservation priority-setting framework for forest tree species at risk from pest & pathogens and other threats. The Project CAPTURE (Conservation Assessment and Prioritization of Forest Trees Under Risk of Extirpation) uses FIA data and expert opinion to group tree species under threat by non-native pests into vulnerability classes and specify appropriate management and conservation strategies. The scientists prioritized 419 tree species native to the North American continent. The analysis identified 15 taxonomic groups requiring the most immediate conservation intervention because of the tree species’ exposure to an extrinsic threat, their sensitivity to the threat, and their ability to adapt to it. Each of these 15 most vulnerable species, and several additional species, should be the focus of both a comprehensive gene conservation program and a genetic resistance screening and development effort.

Carolina ash (Fraxinus caroliniana) and pumpkin ash (F. profunda) are among six species that face severe pest threats, but have a high capacity to adapt (according to CAPTURE project). For these reasons, conservation and the facilitation of resistance through breeding are high priorities.  Several other ash species that have not yet been infested by EAB eventually might experience extensive mortality. Because they tend to be rare, CAPTURE ranked them higher for conservation and the facilitation of resistance then might otherwise be the case. These species are Texas ash (Fraxinus albicans), velvet ash (F. velutina), Chihuahua ash (F. papillosa), fragrant ash (F. cuspidata), Berlandier ash (F. berlandieriana), and Gregg ash (F. greggii)

Since its discovery, emerald ash borer has killed more than 50 million ash trees in North America (GPTF II, 2008). The most widespread ash species — white (Fraxinus americana), black (F. nigra), and green (F. pennsylvanica) – face extensive EAB-caused decline but have the potential advantage of being widespread and common with relatively high genetic variation and regeneration capacity. Despite the breathing room provided by their extensive distributions and relatively higher regeneration capacity and genetic variability, it is important to maintain large populations to reduce the chance of inbreeding. As the emerald ash borer spreads, the damage will mount: an estimated 7.5 billion ash trees are found on timberlands in the U.S. (USDA APHIS 2007); an additional 30-90 million trees are planted in urban areas (USDA APHIS 2007).  While the costs to urban areas have not been systematically estimated, Ann Arbor, Michigan paid nearly $4 million to cut down 10,000 trees (Hiejtfe 2007).  Chicago alone has more than 600,000 ash trees (Nowak, 2008).  The Chicago forestry staff estimate that removal and replacement of the 97,000 ash trees growing along the city’s streets will cost $150 million (McCarthy pers. comm. 2008).  At the leading edge of one outbreak, Milwaukee spent approximately $600,000 to inject pesticides into 13,000 large ash trees in 2009; the City Forester expects to treat more trees in 2010 (Sivyer pers. comm. January 2010). Spread of the emerald ash borer to additional areas over the next 10 years could result in $10 billion or more in costs to urban and suburban areas for tree removal and replacement or chemical treatments (Kovacs et al. 2009).  This estimate is probably low because, while it does include Baltimore and the towns of eastern Iowa, Minnesota, and Wisconsin, it does not include the Plains states. There are more than 4 million ash trees on urban land in Kansas, Nebraska, and North and South Dakota (Rasmussen pers. comm. December 2009).

Millions more ash grow in Canada.

EAB has been shown to attack another, related, genus of trees: fringetrees (Cionanthus spp.).  EAB attacks on this tree were first noticed by Dr. Don Cipollini of Wright State University in Ohio in 2014 (Hannah 2014).  Initially, it was uncertain whether EAB could establish in the new genus.  However, by summer 2015, Dr. Cipollini had demonstrated that EAB has attacked fringetrees across a wide area – including much of Ohio and parts of Illinois.  EAB attacks on fringetrees appear to occur when EAB populations are high (Entomology Today).

White fringetree (C. virinicus) is native to North America; it grows wild from New Jersey south to Florida and west to Texas. It has become popular as an ornamental plant in a wider area of the country.  In laboratory tests,  a few EAB larvae also survived in the more distantly related tree, devilwood (Osmanthus americanus).  EAB did not survive in the Chinese fringetree (Chionanthus retusus).  This tree is native to the same parts of China as is EAB, so it might have evolved chemicals that protect it from the insect (Entomology Today).

While the newly discovered ability of EAB to infest fringetrees might not extend the geographic area vulnerable to EAB invasion, it will increase the numbers of trees killed and associated economic and ecological damage.  For example, in Missouri and Arkansas, white fringetree is one of few trees or shrubs that grow on bald knobs and limestone/dolomite glades in southernmost (LeDoux 2014).

The emerald ash borer is indigenous to Asia and known to occur in China, Korea, Japan, Mongolia, the Russian Far East, and Taiwan. It was probably introduced to North America in wood packaging; USDA APHIS has intercepted the insect 36 times, at ports in eleven eastern states. Those shipments originated from at least eleven countries (Federal Register: October 14, 2003 (Volume 68, Number 198)).

Larvae feed in the phloem and outer sapwood, producing galleries that damage and eventually kill the host. Adults feed on host foliage. In North America the borer has been found only on ash species, but the pest feeds on elm (Ulmus) and Juglandaceae species (walnuts and hickories) in its native range in east Asia (McCullough & Roberts, 2002a and 2002b).

Eradication is no longer feasible for the emerald ash borer. Current programs focus on curtailing human movement of the insect to new areas (which requires detection of outbreaks so as to focus slow-the-spread efforts on protecting actually uninfested areas) and research into long-term control measures including biological control. Eradication of outlying or isolated outbreaks is rarely attempted. The insect’s spread has been aided by movement of nursery stock and especially firewood.  Firewood has been implicated in dozens of infestations found in or near campgrounds, including the first infestations in Missouri, Indiana and West Virginia. Shipments of infested nursery stock were the source of the Maryland infestation and several others in the upper Midwest; in the Maryland case the nursery owner was fined (www.aphis.usda.gov/ppq/ep/eab/background.html). In October 2003, APHIS established a federal quarantine on the movement of firewood derived from any hardwood tree, as well as ash nursery stock, green lumber, and other material, including logs, stumps, roots, branches, and composted and uncomposted chips (Federal Register, October 14, 2003 (Volume 68, Number 198)). This quarantine now applies to more than 223,500 square miles of the 12 affected states (Lucik pers. comm. February 2010). Other regulations restrict importation of ash wood and nursery stock from Ontario. At the urging of the National Plant Board, in October 2008 APHIS issued a regulation requiring heat treatment of all hardwood firewood entering from Canada.
Ash trees are important members of deciduous forests, riparian and wetland vegetation across North America and are co-dominants (for example with maples (Acer) and beeches (Fagus)) in some ecological communities. There are seventeen ash species in North America north of Mexico (Kartesz, 1994) and it is possible the emerald ash borer will attack them all, although susceptibility apparently varies (Haack et al., 2004; McCullough, 2004).  Ashes are particularly important components of rich, mesic woodlands, cove forests, swamps, floodplain and bottomland forests (Wagner 2007), all habitats harboring exceptional biodiversity.  Wagner (2007) lists 21 species of North American butterflies and moths believed to specialists or largely dependent on ash that he fear might be extirpated if the emerald ash borer kills all ash on the North American Continent.  He expresses concern for additional species that feed in part on other genera.

Ash trees that dominate riparian forests on the Pacific slope and the southwestern deserts could also suffer high mortality rates. Wagner (2007) notes that little is known about the lepidopteran associates of these Western ash.
For more information on this pest, please consult


Entomology Today http://entomologytoday.org/2015/07/22/emerald-ash-borer-infestation-of-white-fringetree-found-to-be-widespread/  accessed 8/12/15

The Federal Register. October 14, 2003 (Volume 68, Number 198).  Emerald Ash Borer; Quarantine and Regulations (available by using search engines/retrieval services at http://www.gpoaccess.gov/fr/index.html).

GPTFII 2008. Emerald Ash Borer Fact Sheet. Great Plains Tree and Forest Invasives Initiative. June 2008.

Haack, R. A., T. R. Petrice, D. L. Miller, L. S., Bauer and N. M. Schiff. 2004. Host range of Emerald Ash Borer. p. 38 In V. Mastro and R. Reardon (compilers) Emerald Ash Borer research and technology development meeting, Port Huron Michigan, Sept 30-Oct 1, 2003. USDA Forest Service publication FHTET-2004-02.

Hannah, J. Wright State researcher finds emerald ash borer may have spread to different tree. October 9, 2014

Hieftje, J. 2007. Continental Dialogue on Non-Native Forest Insects and Diseases Annual Meeting, Atlanta, GA January 2007.

Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. Second editon. Timber Press. Portland, OR.

Kovacs, K.F., R.G. Haight, D.G. McCullough, R.J. Mercader, N.W. Siegert, A.M. Liebhold. 2009. Cost of potential emerald ash borer damage in U.S. communities, 2009–2019. Ecological Economics. 2009.

LeDoux, D. Missouri Department of Agriculture. Personal communication 2014.

Lucik, Sharon. 2010. Public Affairs Specialist, United States Department of Agriculture Animal & Plant Health Inspection Service, pers. comm. February 11, 2010.

McCullough, D. G., A. Agius, D. Cappaert, T. Poland, D. Miller and L. Bauer. 2004. Host range and host preference of Emerald Ash Borer. pp. 39-40 In V. Mastro and R. Reardon (compilers) Emerald Ash Borer research and technology development meeting, Port Huron Michigan, Sept 30-Oct 1, 2003. USDA Forest Service publication FHTET-2004-02.

McCullough, D. G., and D. L. Roberts. 2002a. Manuscript Draft for USDA Pest Alert on the emerald ash borer. Deborah McCullough at Department of Entomology, Michigan State University.

McCullough, D. G., and D. L. Roberts. 2002b. Emerald ash borer. Pest Alert. USDA Forest Service, Northeastern Area, State and Private Forestry, 2 pp. http://www.na.fs.fed.us/spfo/pubs/pest_al/eab/eab.pdf.

Nowak, D.J. 2008. Money Matters: $ Facts about ash trees and EAB. Illinois Dept. of Natural Resources. http://dnr.state.il.us/conservation/forestry/Urban/Includes/MoneyMattersUpdate.htm, accessed August 2008.

Potter, K.M., Escanferla, M.E., Jetton, R.M., Man, G., Crane, B.S., Prioritizing the conservation needs of US tree spp: Evaluating vulnerability to forest insect and disease threats, Global Ecology and Conservation (2019), doi: https://doi.org/10.1016/

Siegert, N.W.  2006.  17th USDA Interagency Research Forum on Gypsy Moth and Other Invasive Species. Annapolis, MD. January 10-13, 2006.

Stubbings, G. 2008. Dir. of Plant Health for the Canadian Food Inspection Agency. Personal communication, August 2008.

USDA Animal and Plant Health Inspection Service. Emerald Ash Borer Cooperative Eradication Program in the Lower Michigan Peninsula, Environmental Assessment December 2003.

USDA Animal and Plant Health Inspection Service. 2007. Proposed Release of Three Parasitoids for the Biological Control of Emerald Ash Borer (Agrilus planipennis) in the Continental United States. Environmental Assessment. April 2, 2007.

Wagner, D.L.  2007. Emerald Ash Borer Threatens Ash-feeding Lepidoptera  News of the Lepidopterists’ Society Volume 49, Number 1 (Spring 2007)