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. Outbreaks continue to be found at sites hundreds of miles from the nearest known location – indicating that infested wood continues to be moved.
In Canada, outbreaks have been detected near Ottawa and Montreal--the latter outbreak is near the border with New York and Vermont (Stubbings, 2008). Since its discovery, emerald ash borer has killed more than 50 million ash trees in North America (GPTF II, 2008). 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.
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 (http://www.aphis.usda.gov/newsroom/content/2008/10/firewood.shtml; accesed 2/9/2010).
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.
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.
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.
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.
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)