Emerald ash borer infestation

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Emerald ash borer
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]

Eleven-year cycle: from introduction to large-scale ash death[edit]

The Emerald Ash Borer infestation pattern is similar to a locust plague in that populations grow exponentially after it is introduced into an area. In approximately 11 years, it can wipe out all the ash trees within a sizable perimeter.[example needed] A typical Emerald Ash Borer female will lay approximately 100 eggs during her 2-month life; 56% of these eggs on average will be female.[8] In a typical scenario, each year the EAB population multiplies by a factor of 50. By year 9 of an infestation, the EAB population originating from this one female, will be nearly 1 trillion insects. In year 10 it will be 50 trillion. These insects will then move on and create an expanding wake of destruction.

In individually infested trees, it is difficult to see symptoms in the first 1–2 years of infestation. Typically in the third year after infestation, the tree will exhibit significant dieback. By the end of the 4th year after the original infestation begins, the tree will be dead. After 5 years (1 year after death) the dead ash trees will become brittle and start to drop major limbs. Because the volume of trees that die at one time is often so large, cities and homeowner groups are being caught unprepared and are not able to remove the trees because of the lack of resources as well as available removal services.[9]

Exponential beetle population explosion phase[edit]

It is common for all the trees in a single neighborhood to die at the same time. In a typical small town/city situation, the 4-year period, from year 8 through year 11 after infestation, will see 60 - 70% of their trees die in that region. They are calling this the curve of death because on a graph that charts time and tree death after beetle introduction, the plotted line angles almost straight up during those 4 years, ending in all the local ash trees being dead.[10] As insects migrate, new epicenters of ash tree mortality pop up more and more frequently. These epicenters then begin to coalesce. It is predicted that this pattern will continue until eventually, all the ash trees are dead.[9][11] Recent climate research seems to suggest that EAB growth may be stemmed by areas far too cold for the beetle to survive.[12]

Wake of destruction[edit]

As of April 2012, there are many millions of dead standing trees in Canada and United States. This includes southwestern Ontario, and in the United States, southwestern Michigan, much of Ohio, Indiana, and Illinois. And this scenario is coming soon to Wisconsin, Minnesota, Iowa, Pennsylvania, Maryland, and the east coast.[5] Cities that were not prepared for this onslaught of dead ash trees are now dealing with tree limbs falling and the inability to either raise the dollars or find the skilled manpower needed to remove the trees. Insurance companies are being hit with claims coming from trees falling on vehicles, buildings, and even people. A recent report showed that in a number of studied cities, where emerald ash borer has killed all the ash trees, heart attack rates and lung disease deaths are higher than before the ash died. With 10-25% of their urban canopy gone, air pollution is more prevalent.[9]

Environmental and economic impact[edit]

Cities such as Minneapolis, Minnesota have slightly more than 20% of their urban forest as ash.[13] This is typical, as many cities have high ash populations because of their ability to tolerate urban stress and survive poor planting practices that plague urban cities today. The Minneapolis – Saint Paul metro area has between 2 and 2.5 million ash.

All towns and cities with significant ash populations will be eventually invaded by the Emerald ash borer and go through the EAB curve of death. How a town or a city prepares for this arrival is important. Having no plan will mean trees will die quickly. Dead ash trees will be everywhere, faster than expected. Dealing with this scenario carries a very high cost. However, having a planned management strategy will cost far less, spreading these costs out significantly longer. In addition, important ash trees will be alive for many years - for less expense than removal and replacement.[14][15]

Management planning[edit]

A green ash killed by emerald ash borers

Trees are inventoried based on location, age, value, density, and hazard to determine management priorities for monitoring, treatment and tree removal.[14][16] There is a value calculator for urban trees created by Purdue University, http://extension.entm.purdue.edu/treecomputer/. This can help determine what trees are worth to a city or neighborhood, and is useful in determining which trees should be removed, and which trees are worth saving.[14]

Implementation of a management plan can begin with removing the hazardous and weak trees even if the emerald ash borer has not arrived yet in the area. Purple traps are used to monitor for the presence of emerald ash borer in an area.[17] Ash trees with rougher bark have a higher risk of infestation than others.[18]Trees treated with insecticide will slow down the borers population build up and can be used to allow the city to remove trees as they choose, instead of being forced to remove all their ash trees over a few years.[19]

Preventative treatments[edit]

Insecticides containing three active ingridients for preventing damage are currently recommended: imidacloprid, emamectin benzoate, and dinotefuran.[20] New treatments being tested may soon be recommended as well.[21] However, some marketed products have no proven efficacy. In particular, store-brand 2.94% imidacloprid formulations are effective only on trees having a diameter under 8 inches (20 cm) (DBH). Larger trees require professional-strength formulations with the "2X imidacloprid" label.[20]


Imidacloprid is applied to the soil within 1 foot (30 cm) of the tree trunk. Some imidacloprid products require a license to apply. However, water-soluble and injected flowable imidacloprid is not restricted and homeowners can purchase and protect their own trees without needing a license.[citation needed] Annual treatments are required for continued protection.[20] Imidacloprid can harm water insects and insect larvae if applied directly to water.[22] After application it takes 30 to 60 days for imidacloprid to move up into the tree with enough strength to become effective.[20]

Emamectin Benzoate

Emamectin benzoate is applied through holes that are drilled into the ash trunk. Each hole has a plug that is designed to prevent the solution from coming back out and to create a reservoir from which the solution is absorbed by the tree. Holes must be drilled into the tree every two years. Ash are tough, and could be treated a few times without issue, but over many years drilling and chemical wounds will compromise the tree's health.[23][24] This product is the most toxic to the insect and had the highest score in terms of having the least amount of living larvae in treated trees. Only professional and licensed certified applicators can apply this product.[20] Treatment is effective for two years.[25] It can only be applied by a professional. Homeowners or do-it-yourself people cannot use this product as it is a restricted use material.[26]


Dinotefuran is similar to imidacloprid in that it can be applied to the soil with a soil injector. Its advantage is that it moves into the tree about 3 times faster than imidacloprid. Thus, it can be used later in the season and as a rescue treatment. Dinotefuran can also be sprayed on the trunk of the tree as its high solubility allows it to move through the bark. It is available to homeowners.[citation needed]

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 containers being delivered to Yazaki North America, an automotive parts distributor. 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. [27] 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. This one hung for a few years in Vanderburgh County, Indiana, near Darmstadt.

Introduction of biological control organisms[edit]

As part of the campaign against the emerald ash borer (EAB), American scientists in conjunction with the Chinese Academy of Forestry searched since 2003 for its natural enemies, leading to the discovery of several parasitoid wasps, namely Tetrastichus planipennisi, a gregarious larval endoparasitoid, Oobius agrili, a solitary, parthenogenic egg parasitoid, and Spathius agrili, a gregarious larval ectoparasitoid. These have been introduced and released into the United States of America as a possible biological control of the emerald ash borer. Initial results have shown promise with T. planipennisi, and it is now being released.[28][29] The USDA is assessing the application of Beauveria bassiana (a fungal pathogen with known insecticidal properties) prior to the releasing of T. planipennisi. However, some recent studies have shown that B. bassiana has had deleterious effects on the wasps themselves.[30] Recent studies have also discovered Spathius laflammei and Atanycolus nigropyga, two hymenopteran parasitoid species that are native to North America, that also prey on EAB.[31] It has also recently become possible to fabricate visual decoys of the female EAB, in order to lure in and trap male EAB.[32]

In addition to attempts to control EAB through the introduction of non-native species which kill EAB, government agencies in both the USA and Canada are utilizing a native species of wasp, known as “Smoky-Winged Buprestid Bandit” (Cerceris fumipennis) as a means of detecting areas to which EAB has spread. 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 and supervising the volunteers know that proper quarantine measure must be instituted. This methodology is known as biological monitoring, as opposed to control, because it does not appear that the wasps have a significant negative impact on EAB populations.[33]

Modern day extinction event[edit]

Unlike Dutch elm disease that allows elm trees to seed new generations before killing them off around 15 years of age, the Emerald Ash Borer kills young trees when only 1" DBH in size, or several years before reaching their seeding age of 10. Field studies of the first Michigan forests which succumbed to EAB earlier in this event showed that the borer had gluttonously killed off all living Fraxinus of every age and type within them. Forest floor samples of these same plots resulted in ground soils void of seeds which could be capable of germinating continued generations.

Private Michigan arborist Wayne A. White who had received credit for being the first to make progress against EAB by utilizing systemic insecticides back in 2002 has already been advising his customers who have six or eight years of treatment build-up in their tree on reducing to a self-applied soil drench treatment. He further suggests that they begin treating every other year until scientists make an official statement.[34][35]

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. 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. ^ a b "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 Arbor age magazine, April 2012. Emerald Ash Borer, Brad Bonham
  10. ^ "Task Force Projects and Information". New York Invasive Species Information. Cornell University. Retrieved August 30, 2013. 
  11. ^ Dan Herms -Professor, Ohio State University
  12. ^ 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. 
  13. ^ "Emerald Ash Borer". Urban Forest. Minneapolis Park and Recreation Board. Retrieved August 29, 2013. 
  14. ^ a b c Sadof, Cliff, Developing an EAB Management Strategies for Properties and Cities, Purdue University Department of Entomology, retrieved August 29, 2013 
  15. ^ Emerald Ash Borer Management Statement, Coalition for Urban Ash Tree Conservation, January 6, 2011, retrieved August 29, 2013 
  16. ^ Emerald Ash Borer Management Plan, Ohio Department of Natural Resources Division of Forestry, retrieved August 30, 2013 
  17. ^ Francese, Joseph A.; et al (2008). "Influence of Trap Placement and Design on Capture of the Emerald Ash Borer (Coleoptera: Buprestidae)". Journal of Economic Entomology 101 (6): 1831–1837. Retrieved 27 September 2013. 
  18. ^ Marshall, Jordan M.; Eric L. Smith, Roger Mech and Andrew J. Storer (January 2013). "Estimates of Agrilus planipennis infestation rates and potential survival of ash". The American Midland Naturalist 169 (1): 179. 
  19. ^ Steps in Implementing a Strategy to Slow Ash Mortality, USDA Forest Service, Michigan State University, March 2010, retrieved August 30, 2013 
  20. ^ a b c d e 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 
  21. ^ Herms, Dan, Insecticide Options for Successful Management of Emerald Ash Borer, Ohio State University, retrieved August 30, 2013 
  22. ^ "Imidacloprid Technical Fact Sheet". National Pesticide Information Centre. Retrieved August 30, 2013. 
  23. ^ 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. 
  24. ^ Shigo, Alex L.; Campana, Richard (December 1977). "Discolored and decayed wood associated with injection wounds in American Elm". Journal of Arboriculture (International Society of Arboriculture) 3 (12): 230–235. Retrieved August 30, 2013. 
  25. ^ 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 
  26. ^ product label - http://www.treecarescience.com/uploads/100344TREE-age_full_label_4-15-11.pdf
  27. ^ "Emerald ash borer". USDA Forest Service. August 14, 2006. Retrieved April 15, 2014. 
  28. ^ 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 
  29. ^ 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. 
  30. ^ "Biocontrol: Fungus and Wasps Released to Control Emerald Ash Borer". Science News. Science Daily. May 2, 2011. Retrieved August 30, 2013. 
  31. ^ Duan, Jian J.; et al (March 2013). "Hymenopteran Parasitoids Attacking the Invasive Emerald Ash Borer (Coleoptera: Buprestidae) in Western and Central Pennsylvania". Florida Entomologist 96 (1): 166. Retrieved 27 September 2013. 
  32. ^ Pulsifer, Drew P.; et al (April 2013). "Fabrication of Polymeric Visual Decoys for the Male Emerald Ash Borer (Agrilus planipennis)". Journal of Bionic Engineering 10 (2): 129–138. Retrieved 27 September 2013. 
  33. ^ Zirlin, Harry (August 23, 2012). "American Wasps Sniff Out Foreign Beetles". H. Zirlin's Insect Blog. Halcyon Solutions Inc. Retrieved August 30, 2013. 
  34. ^ "Will I Have to Treat for Emerald Ash Borer Forever?". 
  35. ^ Klooster, Wendy. "Emerald Ash Borer Invasion of North American Forests". www.emeraldashborer.info. Retrieved August 30, 2013. 

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