Emerald ash borer

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For the infestation of this insect in North America, including control methods, see Emerald ash borer infestation.
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

The emerald ash borer (Agrilus planipennis) is a green beetle native to Asia and Eastern Russia.[2] Outside its native region, the emerald ash borer (also referred to as EAB) is an invasive species, and emerald ash borer infestation is highly destructive to ash trees in its introduced range.[3] The Emerald Ash Borer was first discovered in America in June 2002 in Michigan. It is believed to have been brought to America unintentionally in ash wood which was used to stabilize crates during shipping.

Life cycle[edit]

Underside of Agrilus planipennis
Agrilus planipennis mating

A. planipennis may take one or two years to complete its life-cycle depending on 1) the timing of egg deposition, 2) the health and stress level of the tree, and 3) local temperatures. The one-year EAB life-cycle is described below.[4]

Adults The adult beetle is dark metallic green, bullet-shaped and about 8.5 millimetres (0.33 in) long and 1.6 mm (116 in) wide. The body is narrow and elongated, and the head is flat with black eyes. Adults begin to emerge from the trunks of ash trees after the accumulation of 400-500 growing degree days base 50 °F (GDD). Peak adult emergence occurs at ~1000 GDD. After emergence, adults fly into the ash canopy where they feed on leaves throughout their lives. EAB adults start mating one week after emergence, and females begin laying eggs 2–3 weeks later. A typical female will lay approximately 100 eggs during her 2-month life; 56% of these eggs on average will be female. [5] In the field, EAB adults are readily observed mating and egg-laying on the trunks of ash trees on warm, sunny afternoons and evenings. The adults of both sexes are strong fliers.[4]

Eggs A female EAB may lay >100 eggs in her lifetime, depositing them individually or in groups on the bark along the trunk and portions of the major branches. Eggs are laid in areas where the bark is rough, and between bark layers or in bark crevices. Eggs are approximately 1.0 mm long x 0.6 mm wide and creamy white when laid; fertile eggs gradually turn amber after a few days. The eggs hatch after about two weeks.[4]

Larvae Newly hatched larvae bore through the bark to the phloem and outer layer of new sapwood where they feed until the weather gets too cold in the fall. There are four stages of larval development (instars). As they feed, the larvae create long serpentine galleries filled with frass, which enlarge in width as they grow. Larvae are creamy white, and dorso-ventrally flattened. When fully mature, fourth-instar larvae are 26 to 32 mm long. Their head is mostly retracted into the prothorax with only the dark brown mouthparts visible. The prothorax is enlarged, with the mesothorax and metathorax more narrow. Larvae have 10 bell-shaped abdominal segments and a pair of small brown structures called urogomphi, which are characteristic of all larvae in the genus Agrilus.[4]

Overwintering larvae, pre-pupae, pupae, and adults In the fall, mature fourth-instar EAB larvae excavate pupal chambers in the sapwood or outer bark where they fold into overwintering “J-shaped larvae”. In the spring, the J-shaped larvae shorten into prepupae then shed their cuticle to become naked pupae. Pupae are initially creamy white, but the eyes turn red and the body begins to darken as they develop. To emerge from ash trees, adults chew D-shaped exit holes through the bark and are capable of immediate flight upon emergence. EAB larvae that are immature as cold weather arrives in the fall will simply overwinter in their larval gallery. Larger larvae complete development the following spring, whereas smaller larvae may require another summer of feeding to complete development.[4]

Effect on trees[edit]

The most significant damage to a tree by the emerald ash borer takes place when the insect is in its larval stage. The larvae feed on the conductive tissue of the tree. This tissue is what transfers the nutrients and water from the roots to the leaves, and when this is disturbed, the tree begins to die. At the onset of winter, the larvae relocate to the bark of the tree, effectively cutting off the tissue more. This ultimately results in the death of tree.[6] This can take place over a number of years, and the first noticeable sign is usually some die back in the crown of the tree. The tree will usually be dead by the following year or soon after. In areas where the insect is invasive and has no natural predators, it can and usually does have a devastating effect on the local ash tree population.


Prevention of EAB is possible by the use of a systemic insecticide into the base of the tree.[7] This treatment can prevent damage to the tree for up to two years. Note that application must be reapplied every two years. Soil injections are another option for the prevention of EAB. These insecticides are injected directly into the soil surrounding the base of the tree, and are then transported through the rest of the tree via the roots. In order for these treatments to have the greatest effect soil must be moist when applied. Water logged or dry soils will result in less of the insecticide to be absorbed into the tree. There are two insecticide spray treatments that can be used as well. The first is a spray which is applied to the trunk and absorbed through the bark. This treatment is less invasive to the tree and soil, however if the tree has thick bark absorption is slow and limited. The second spray treatment is a protective cover spray, which is applied to the branches and trunk of the tree. This treatment kills adult beetle and newly hatched larva; however it will not kill eggs.

Invasive Nature[edit]

For an article detailing the infestation of this insect in North America, including control methods, see Emerald ash borer infestation.

North America[edit]

It is estimated that there are 8 billion ash trees in the United States. Since the arrival of the Emerald Ash Borer, approximately 150-200 million ash trees have already died and this number is expected to rise.[8] The EAB travels by the movement of firewood and nursery stock. The beetle, once in its adult life stage, can also fly up to a half mile under its own power. The Emerald Ash Borer has spread to 22 states within the United States as well as Canada, since its discovery in North America in 2002. This map details the spread of the emerald ash borer. Certain areas in North America have been federally quarantined by the United States and Canadian national governments to prevent the spread of the EAB into other areas forested by ash trees. The largest area consists of the region stretching from the midwestern area of the United States to the eastern coast.

Disruption of Species[edit]

Polar Vortex of 2014[edit]

In early 2014, the midwestern and northern parts of the United States were hit with below average freezing temperatures brought about by a polar vortex. These areas in the United States experienced temperatures ranging from -16 °F to 0 °F[citation needed]. The EAB is said to be able to persist at temperatures as low as (-16 °F), making scientists cautious as to predict their partial attrition by this weather event[citation needed]. Emerald ash borers retain a certain coping mechanism in cases of extreme cold; they purge their gut contents which have the propensity to freeze and fold their bodies in half to reduce their size.[6] This allows the EAB to sustain periods of time of extreme cold, such as a polar vortex.[9] Once the polar vortex had passed, researchers with the U.S. Forest Service reported EAB attrition rates as high as 80% in some areas of Minnesota.[10] The EAB is expected to come back, as not all areas infested with EAB experienced cold enough temperatures to threaten the insect.

Effects on human economy and natural environment[edit]

Emerald ash borers undoubtedly affect commerce in ash tree products in North America. The predominant type of ash in North America, white ash, is used in residential construction and for various commercial products. Some examples include flooring, baseball bats, and electric guitars.[10] The consequences of a decrease in the supply of the wood can be predicted in general, but not in detail. The Ohio Department of Natural Resources published a report[11] detailing the effects of the emerald ash borer on that State's economy and beyond, including the predictably massive cost of tree removal from residential areas.[12] That figure is estimated to be in the billions of dollars nationwide.[13] Retailers of ash trees can also expect the numbers to change as more and more stocks of ash trees are deemed defective and unsalable. Sawmills throughout the affected regions rely heavily on ash products for revenue, and an expected decrease in the supply of ash trees will plainly affect them. At least six species of ash are considered commercially important, and in the eastern United States 7.5% of total sawmill volume comes from ash trees.[8]

White ash supports a wide variety of plant and animal species in its range, stretching from east Texas into Maine.[14] The reduction in ash populations by emerald ash borers causes harm to the ecosystem for both plant and animal species, extending the borer's environmental effects far beyond the damage it causes directly.[14] As ash trees die, the resulting gaps in the leafy canopy expose the forest understory to sunlight, which disturbs shade-loving plants and animals that dwell there.[14] Reductions in tree populations injure nearby human communities as well, by destroying exploitable timber, and reducing the appeal of natural areas.[11] Ashes account for a large percentage of the United States' northern forests.[8] Removal of infested ash trees from neighborhoods and parks diminishes the natural beauty of such areas, and can cost billions of dollars.[8][15] The intrinsic value of national, state, and local parks continues to be eroded by the persistence of the emerald ash borer.

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. ^ a b c d e Gould, Juli S.; Bauer, Leah S.; Lelito, Jonathan; Duan, Jian (May 2013). Emerald Ash Borer Biological Control Release and Recovery Guidelines. Riverdale, Maryland, USA: USDA-APHIS-ARS-FS. Retrieved August 28, 2013{{inconsistent citations}} 
  5. ^ 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. 
  6. ^ a b Schaper, David. "The Upside Of The Bitter Cold: It Kills Bugs That Kill Trees". NPR. Retrieved 2 March 2014. 
  7. ^ Herms, et al. "Insecticide Options for Protecting Ash Trees from Emerald Ash Borer". Retrieved 14 May 2014. 
  8. ^ a b c d Poland, Therese; Deborah McCullough (April–May 2006). "Emerald Ash Borer: Invasion of the Urban Forest and the Threat to North America’s Ash Resource". Journal of Forestry. 
  9. ^ Matus, Morgan. "Polar Vortex’s Possible Only Benefit is That It Helped Kill Off Some Invasive Insects". Inhabitat LLC. Retrieved 2 March 2014. 
  10. ^ a b Fears, Darryl. "Winter’s freeze stopped ash borers and stink bugs cold, but they’re primed for a comeback". The Washington Post. Retrieved 2 March 2014. 
  12. ^ Sydnor, T.Davis; Matthew Bumgardner Andrew Todd (2007). "The Potential Economic Impacts of Emerald Ash Borer (Agrilus planipennis) on Ohio, U.S., Communities". Arboriculture & Urban Forestry. Retrieved 1 April 2014. 
  13. ^ Kovacs, Kent; Robert G. Haight; Deborah G. McCullough; Rodrigo J. Mercader; Nathan W. Siegert; Andrew M. Liebhold (15 January 2010). "Cost of potential emerald ash borer damage in U.S. communities, 2009–2019". Ecological Economics 69 (3). Retrieved 1 April 2014. 
  14. ^ a b c Rice, Kevin. "Emerald Ash Borer Invasion of North American Forests". Retrieved 1 April 2014. 
  15. ^ "Dynamics of Surviving Ash (Fraxinus spp.) Populations in Areas Long Infested by Emerald Ash Borer (Agrilus planipennis)". Retrieved 2 March 2014. 

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