Emerald ash borer

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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

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. 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.[5] 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. 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]

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.[6] 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.[5] This allows the EAB to sustain periods of time of extreme cold, such as a polar vortex.[7] 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.[8] The EAB is expected to come back, as not all areas infested with EAB experienced cold enough temperatures to threaten the insect.

Economic impact and ecosystem and human relations[edit]

Emerald ash borers undoubtedly affect the commerce of ash tree products in North America. The predominant type of ash tree in North America, White ash, is used for various residential and commercial purposes. Some examples include flooring, baseball bats, electric guitars, and bowling alleys.[8] The decrease in the supply of this product has predictable, yet unknown precise consequences. The Ohio Department of Natural Resources published a report[9] detailing the economic impact of the emerald ash borer on the state's economy. Evident are the untold costs of residential tree removal in Ohio, and furthermore across the country.[10] This figure is estimated to be in the billions of dollars nationwide.[11] Retailers of ash trees can also expect the numbers to change as more and more stocks of ash trees are deemed defective and unable to sell. Sawmills across the regions rely heavily on ash product as revenue, and an expected decrease in the supply of ash trees will unambiguously affect these businesses. At least six species of ash trees are considered commercially important, and in the eastern United States 7.5% of total sawmill volume comes from ash trees.[6]

White ash trees support a wide variety of plant and animal species ranging from east Texas and extending into Maine.[12] The reduction in ash trees due to emerald ash borers will negatively affect the ecosystem of both plant and animal species, further heightening the impact that the invasive emerald ash borer has.[12] As ash trees die, their foliage dies too and opens the understory of a forest to sunlight. The sunlight disturbs the previous equilibrium of the forest, adversely affecting the many bugs, insects, plants and animals that colonize in the area.[12] Reductions in tree populations adversely affect human populations in the area by decreasing logging potential and the intrinsic value of nature.[9] The human relationship with ash trees remains partially unclear, but ash trees account for a large percent of the United State's northern forests.[6] Ash trees that must be removed from neighborhoods and parks due to infestation decrease the intrinsic value of the area and can cost upwards of billions of dollars in largely populated areas.[6][13] The intrinsic value of national, state, and local parks will suffer due to 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 
  5. ^ a b Schaper, David. "The Upside Of The Bitter Cold: It Kills Bugs That Kill Trees". NPR. Retrieved 2 March 2014. 
  6. ^ 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. 
  7. ^ Matus, Morgan. "Polar Vortex’s Possible Only Benefit is That It Helped Kill Off Some Invasive Insects". Inhabitat LLC. Retrieved 2 March 2014. 
  8. ^ 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. 
  10. ^ 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. 
  11. ^ 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. 
  12. ^ a b c Rice, Kevin. "Emerald Ash Borer Invasion of North American Forests". Retrieved 1 April 2014. 
  13. ^ "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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