Emerald ash borer infestation

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Emerald ash borer
Agrilus planipennis 001.jpg
Scientific classification e
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Buprestidae
Tribe: Agrilini
Genus: Agrilus
Species: A. planipennis
Binomial name
Agrilus planipennis
Fairmaire, 1888
  • Agrilus feretrius Obenberger
  • Agrilus marcopoli Obenberger

Outside its native region (Asia and Eastern Russia [2]), the emerald ash borer Agrilus planipennis is an invasive species, highly destructive to ash trees in its introduced range.[3] The potential damage of this insect rivals that of Chestnut blight and Dutch elm disease. Since its accidental introduction into the United States and Canada in the 1990s and its subsequent detection in 2002,[4] it has spread to 14 states and adjacent parts of Canada.[5] It has killed at least 50 to 100 million ash trees so far and threatens to kill most of the 8.7 billion ash trees throughout North America.[6] The emerald ash borer is now one of the most destructive non-native insects in the United States; it and other wood-boring pests cause an estimated $3.5 billion in annual damages in the U.S.[7]

The insect threatens the entire North American Fraxinus genus, unlike past invasive tree pests in North America, which have only threatened a single species within a genus. The green ash and the black ash trees are preferred. White ash is also killed rapidly, but usually only after green and black ash trees are eliminated. Blue ash displays some resistance to the emerald ash borer by forming callous tissue around EAB galleries; however, usually they are eventually killed also.[8]

Invasiveness and spread[edit]

Without factors that would normally suppress EAB populations in its native range (e.g., resistant trees, predators, and parasitoid wasps), EAB populations can quickly rise to damaging levels.[9] All North American ash species show susceptibility to EAB as North American species planted in China also show high mortality due to EAB infestation, but some Chinese species show resistance.[10][11] Green ash and the black ash trees are preferred by EAB. White ash is also killed rapidly, but usually only after green and black ash trees are eliminated. Blue ash displays some resistance to the emerald ash borer by forming callous tissue around EAB galleries; however, usually they are also eventually killed.[8] Upon the arrival of EAB in North America, many of the specialized predators and parasitoids that suppressed its populations in Asia were not present in North America. Predators and parasitoids native to North America do not sufficiently suppress EAB, so populations continue to grow and kill nearly 100% of ash trees in an area approximately 10 years after introduction.[9][12] EAB populations can spread 20 km a year. [9] However, it primarily spreads long-distance by transport of firewood and other wood products that contain ash bark, which allows EAB to spread to new areas to create satellite populations outside of the main infestation and quickly increase its range.[9]

A green ash killed by emerald ash borers

Other factors can limit spread. Climate research suggests that EAB growth may be stemmed in areas too cold for the beetle to survive.[13][14] North American predators and parasitoids can cause high EAB mortality occasionally, but generally offer limited control. Mortality due to woodpeckers is variable, and parasitism by parasitoids such as Atanycolus cappaerti can be high, but overall parasitism is generally low.[9]

Spread over time[edit]

The natural range of the emerald ash borer is eastern Russia, northern China, Japan, and Korea. Its first confirmed North American detection was in June 2002 in Canton, Michigan. It is suspected, that it was introduced by overseas shipping materials. [15] It has since been found in several other parts of the North America. Ohio, Minnesota, and Ontario have experienced emerald ash borer migration from Michigan, and has continued to spread across the continent. [16] Authorities across the US are continuing to determine the exact extent of EAB by placing purple traps nationwide.

A purple trap used for determining the extent of the invasion.

Environmental and economic impacts[edit]

EAB threatens the entire North American Fraxinus genus. It has killed at tens of millions of ash trees so far and threatens to kill most of the 8.7 billion ash trees throughout North America.[17] Emerald ash borer kills young trees several years before reaching their seeding age of 10 years. Field studies of the first Michigan forests first infested with EAB showed that the borer had killed off >99% of all living Fraxinus. Forest floor samples of these same plots resulted in ground soils void of seeds which could be capable of germinating continued generations.[18] The loss of ash from an ecosystem can result in increased numbers of invasive plants, changes in soil nutrients, and effects on species that feed on ash.[9]

Damage and efforts to control the spread of EAB have affected businesses that sell ash trees or wood products, property owners, and local or state governments.[9] Quaratines can limit the transport of ash trees and products. Economic impacts are especially high for urban and residential areas due to treatment or removal costs and decreased land value from dying trees. Costs for managing these trees can fall upon homeowners or local municipalities. For municipalities, removing large numbers of dead or infested trees at once is costly, so slowing down the rate at which trees die through removing known infested trees and treating trees with insecticides can allow local governments more time to plan, remove, and replace trees that would eventually die. This strategy saves money as it would cost $10.7 billion in urban areas of 25 states between 2009-2019, while removing and replacing all ash trees in these same areas at once would cost $25 billion. [19] Some urban areas such as Minneapolis, Minnesota, have large amounts of ash with slightly more than 20% of their urban forest as ash.[20]

Monitoring and Management[edit]

In areas where EAB has not yet been detected, surveys are used to monitor for new infestations. Visual surveys are used to find ash trees displaying symptoms of EAB damage and colored traps attractive to EAB are hung in trees as part of a monitoring program. Sometimes trees are also girdled to act as a trap tree by attracting egg-laying female EAB in the spring and debarking the trees in the fall to search for larvae.[9] If detected, the area is typically placed under a quarantine to prevent infested wood material from causing new infestations.[21] Further control measures are then taken within the area to slow population growth by reducing EAB numbers, preventing them from reaching reproductive maturity and dispersing, and reducing the abundance of ash trees.[9]

Government agencies in both the USA and Canada have utilized a native species of wasp, Cerceris fumipennis, as a means of detecting areas to which EAB has spread.[22] The females of these wasps hunt beetles in the same family as EAB and, therefore, will hunt EAB if it is present. The wasps stun the beetles and carry them back to their burrows in the ground where they are stored until the wasps’ eggs hatch and the wasp larvae feed on the beetles. Volunteers catch the wasps as they return to their burrows carrying the beetles to determine whether any of the catch consists of EAB. If it does, the agencies running the program know that proper quarantine measure must be instituted. This methodology is known as biological surveillance, as opposed to biological control, because it does not appear that the wasps have a significant negative impact on EAB populations.[23]

Once EAB is established in an area, multiple control measures can be used as part of an integrated pest management program.[24]

Tree removal and replacement[edit]

In urban areas, trees are often removed once an infestation is found to reduce EAB population densities and the likelihood of further spread. Urban ash are typically replaced with non-ash species such as maple, oak, or linden to limit food sources for EAB.[25] In rural areas, trees can be harvested for lumber or firewood to reduce ash stand density, but quarantines may apply, especially in areas where the material could be infested.[26]


Insecticides are typically only recommended in urban areas or high value trees near an infestation. Insecticides with active ingredients such as imidacloprid, emamectin benzoate, and dinotefuran are currently recommended since they are systemic (i.e., incorporated into the tree) and remain effective for one to three years depending on the product.[9][27][28] Ash trees are primarily treated by direct injection into the tree or soil drench. Some insecticides cannot be applied by homeowners and must be applied by licensed applicators canInitially, tree injections will not compromise tree health, but over many years drilling and chemical wounds will compromise the tree's health.[29] Damage from EAB can continue to increase over time even with insecticide applications.[9] Insecticide treatments are not feasible for large forested areas outside of urban areas.[9]

Biological Control[edit]

The native range of EAB in Asia was surveyed for parasitoid species that parasitize EAB and do not attack other insect species in the hope they would surpress EAB populations when released in North America. [30]Three species imported from China are currently approved by the USDA for release: Spathius agrili, Tetrastichus planipennisi, and Oobius agrili.[31] All three species have been documented parasitizing EAB larvae one year after release indicating they survived the winter.[32][33]

The USDA is also assessing the application of Beauveria bassiana, an insect fungal pathogen, for controlling EAB in conjunction with parasitoid wasps.[34]

See also[edit]


  1. ^ "Data sheets on quarantine pests: Agrilus planipennis". OEPP/EPPO Bulletin (European and Mediterranean Plant Protection Organization) 35 (3): 436–438. 2005. doi:10.1111/j.1365-2338.2005.00844.x. Retrieved August 28, 2013. 
  2. ^ "Agrilus planipennis (insect)". Global Invasive Species Database. ISSG-IUCN. August 14, 2006. Retrieved August 28, 2013. 
  3. ^ "Emerald Ash Borer". Don't Move Firewood. Retrieved August 28, 2013. 
  4. ^ "Forest Health Protection - Emerald Ash Borer". Northeastern Area. US Forest Service. Retrieved August 28, 2013. 
  5. ^ "Initial county EAB detections in North America". Cooperative Emerald Ash Borer Project. United States Department of Agriculture. August 5, 2013. Retrieved August 30, 2013. 
  6. ^ "emerald ash borer". USDA Forest Service, Michigan State University. Retrieved August 28, 2013. 
  7. ^ "Economic Impacts of Non-Native Forest Insects in the Continental United States". Journalist's Resource: Ecology, Real Estate. Harvard Kennedy School. Retrieved August 28, 2013. 
  8. ^ a b Anulewicz, Andrea C.; McCullough, Deborah G.; Cappaert, David L. (September 2007). "Emerald Ash Borer (Agrilus planipennis) Density and Canopy Dieback in Three North American Ash Species". Aboriculture & Urban Forestry (International Society of Aboriculture) 33 (5): 338–349. Retrieved August 29, 2013. 
  9. ^ a b c d e f g h i j k l Herms, Daniel A.; Deborah G. McCullough (October 9, 2013). "Emerald Ash Borer Invasion of North America: History, Biology, Ecology, Impacts, and Management". Annu. Rev. Entomol. 59: 13-30. Retrieved 21 May 2014. 
  10. ^ Lui, Houping; et al. (2003). "Exploratory survey for the emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), and its natural enemies in China.". Great Lakes Entomologist 36: 191-204. Retrieved 28 May 2014. 
  11. ^ Rebek, Eric J.; et al. (2013). "Interspecific Variation in Resistance to Emerald Ash Borer (Coleoptera: Buprestidae) Among North American and Asian Ash (Fraxinus spp.)". Environmental Entomology 37: 242-246. Retrieved 21 May 2014. 
  12. ^ Klooster, Wendy S.; et al. (August 20, 2013). "Ash (Fraxinus spp.) mortality, regeneration, and seed bank dynamics in mixed hardwood forests following invasion by emerald ash borer (Agrilus planipennis)". Biol. Invas. 16: 859-873. Retrieved 30 June 2014. 
  13. ^ DeSantis, Ryan D.; et al (April 21, 2013). "Effects of climate on emerald ash borer mortality and the potential for ash survival in North America". Agricultural and Forest Meteorology 178: 120. Retrieved 27 September 2013. 
  14. ^ "The Upside Of The Bitter Cold: It Kills Bugs That Kill Trees". National Public Radio. Retrieved May 21, 2014. 
  15. ^ Cappaert, D.; et al. (Fall 2005). "Emerald ash borer in North America: a research and regulatory challenge.". Am. Entomol. 51: 152–163. Retrieved July 8, 2014. 
  16. ^ "Emerald ash borer". USDA Forest Service. August 14, 2006. Retrieved April 15, 2014. 
  17. ^ "emerald ash borer". USDA Forest Service, Michigan State University. Retrieved August 28, 2013. 
  18. ^ Klooster, Wendy S.; et al. (April 2014). "Ash (Fraxinus spp.) mortality, regeneration, and seed bank dynamics in mixed hardwood forests following invasion by emerald ash borer (Agrilus planipennis)". Biological Invasions 16 (4): 859–873. Retrieved May 21, 2014. 
  19. ^ Kovacs, K. F.; et al. (September 2009). "Cost of potential emerald ash borer damage in U.S. communities, 2009-2019.". Ecological Economics 69 (3): 569–578. Retrieved May 21, 2014. 
  20. ^ "Emerald Ash Borer". Urban Forest. Minneapolis Park and Recreation Board. Retrieved August 29, 2013. 
  21. ^ "Emerald ash borer map". USDA Forest Service. August 14, 2006. Retrieved April 15, 2014. 
  22. ^ "Working with Cerceris fumipennis". August 23, 2012. Retrieved July 29, 2014. 
  23. ^ Careless, Philip; et al. (February 2014). "The use of Cerceris fumipennis (Hymenoptera: Crabronidae) for surveying and monitoring emerald ash borer (Coleoptera: Buprestidae) infestations in eastern North America". Canadian Entomologist 146: 90-105. 
  24. ^ "SLAM: SLow Ash Mortality". 
  25. ^ "Ash replacement information". USDA Forest Service. Retrieved July 15, 2014. 
  26. ^ "SLAM: SLow Ash Mortality". 
  27. ^ Herms, Daniel A.; McCullough, Deborah G.; Smitley, David R.; Sadof, Clifford S.; Williamson, R. Chris; Nixon, Phillip L. (June 2009), "Insecticide Options for Protecting Ash Trees from Emerald Ash Borer", North Central IPM Center Bulletin (North Central IPM Center): 12, retrieved August 30, 2013 
  28. ^ Hahn, Jeffrey; Herms, Daniel A.; McCullough, Deborah G. (February 2011), Frequently Asked Questions Regarding Potential Side Effects of Systemic Insecticides Used to Control Emerald Ash Borer, www.emeraldashborer.info, retrieved August 30, 2013 
  29. ^ Doccola, Joseph J.; Smitley, David R.; Davis, Terrance W.; Aiken, John J.; Wild, Peter M. (January 2011). "Tree Wound Responses Following Systemic Insecticide Trunk Injection Treatments in Green Ash (Fraxinus pennsylvanica Marsh.) as Determined by Destructive Autopsy". Aboriculture & Urban Forestry (International Society of Arboriculture) 37 (1): 6–12. Retrieved August 30, 2013. 
  30. ^ Bauer, L.S.; Liu, H-P; Miller, D.; Gould, J. (2008). "Developing a classical biological control program for Agrilus planipennis (Coleoptera: Buprestidae), an invasive ash pest in North America". Newsletter of the Michigan Entomological Society 53 (3&4): 38–39. Retrieved 29 April 2011. 
  31. ^ . United States Department of Agriculture Forest Service http://www.nrs.fs.fed.us/disturbance/invasive_species/eab/control_management/biological_control/.  Missing or empty |title= (help)
  32. ^ Hanson, Anthony A.; et al. (August 2013). "Cold tolerance of Chinese emerald ash borer parasitoids: Spathius agrili Yang (Hymenoptera: Braconidae), Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), and Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae)". Biological Control 67: 516–529. 
  33. ^ Gould, Juli; Bauer, Leah, "Biological Control of Emerald Ash Borer (Agrilus planipennis)", Animal and Plant Health Inspection Service (APHIS) website (United States Department of Agriculture), retrieved 28 April 2011 
  34. ^ "Biocontrol: Fungus and Wasps Released to Control Emerald Ash Borer". Science News. Science Daily. May 2, 2011. Retrieved August 30, 2013. 

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