Agrilus planipennis

Name:   Agrilus planipennis
Pest Authorities:  Fairmaire
Taxonomic Position:  Insecta: Coleoptera: Buprestidae
Sub-specific Taxon:  
Pest Type:   Insect
Common Name(s):
   Emerald ash borer, EAB (English)
   Agrilus feretrius Obenberger
   Agrilus marcopili Obenberger
   Agrilus marcopoli ulmi Kurowasa
Numerical Score:  9
Relative Risk Rating:  Very High Risk
Uncertainty:   Very Certain
Establishment Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism has successfully established in location(s) outside its native distribution
  • Suitable climatic conditions and suitable host material coincide with ports of entry or major destinations.
  • Organism has demonstrated ability to utilize new hosts
  • Organism has active, directed host searching capability or is vectored by an organism with directed, host searching capability.
  • Organism has high inoculum potential or high likelihood of reproducing after entry.
Justification: Agrilus planipennis was discovered infesting ash trees in southeastern Michigan in May and June 2002. As of September 2003, this insect was known to occur in 13 counties in Michigan, 4 in Ohio and 1 in Ontario, Canada. It has also been found in ash nursery stock in Maryland and Virginia. Ash is an important component of forests in the northeastern and north central U.S. and adjoining Canada. In addition, 16 species of ash are found throughout much of North America including portions of Mexico (Little 1979). Therefore, this insect would find suitable hosts and climatic conditions at many North American ports of entry. This insect has demonstrated ability to utilize new hosts (Fraxinus americana, Fraxinus pennsylvanica and Fraxinus nigra). It has a directed host searching capability and a demonstrated likelihood of successfully reproducing following introduction.

Spread Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism is capable of dispersing more than several km per year through its own movement or by abiotic factors (such as wind, water or vectors).
  • Organism has demonstrated the ability for redistribution through human-assisted transport.
  • Organism has a high reproductive potential
  • Potential hosts have contiguous distribution.
  • Newly established populations may go undetected for many years due to cryptic nature, concealed activity, slow development of damage symptoms, or misdiagnosis.
  • Eradication techniques are unknown, infeasible, or expected to be ineffective.
  • Organism has broad host range.
Justification: Adults can fly distances of over 1 km in search of host material and, since they are relatively small, are subject to dispersal by air currents. This insect was probably introduced into southeastern Michigan via wooden containers, pallets or dunnage made from ash wood. It has a high reproductive potential and various species of ash are important components of forests in the eastern U.S. and Canada. Moreover, a number of species of Fraxinus are also found in the southwestern U.S. and Mexico (Little 1979). Because of its cryptic nature, newly established infestations might be difficult to detect. For example, the present infestation in Michigan is believed to have existed for 5 to 10 years before it was detected. Eradication and pest management techniques are being developed.

Economic Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism attacks hosts or products with significant commercial value (such as for timber, pulp, or wood products.
  • Organism directly causes tree mortality or predisposes host to mortality by other organisms.
  • Damage by organism causes a decrease in value of the host affected, for instance, by lowering its market price, increasing cost of production, maintenance, or mitigation, or reducing value of property where it is located.
  • Organism may cause loss of markets (domestic or foreign) due to presence and quarantine significant status.
  • No effective control measure exists.
Justification: Agrilus planipennis has already killed thousands of ash trees since it became established in the north central region of North America. The wood of ash is an attractive, durable wood that is widely used in the furniture industry and for production of tool handles and baseball bats. Ash trees are also popular ornamental and shade trees in many parts of North America. This insect has already had a devastating affect on forests with a significant ash component and in areas where ash is widely used as an urban tree. Quarantines designed to reduce the rate of spread of this insect could affect marketability and transport of ash lumber, nursery stock, firewood and related products.

Environmental Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism is expected to cause significant direct environmental effects, such as extensive ecological disruption or large scale reduction of biodiversity.
  • Introduction of the organism would likely result in control/eradication programs that may have potential adverse environmental affects.
Justification: This insect could cause major ecological disruptions in forests with a significant component of ash, resulting in altered tree species composition and reduced biodiversity. Possible use of chemical insecticides for eradication or prevention of attack could have undesirable side effects.

In China, species of ash, Fraxinus sp. are attacked, including Chinese ash, Fraxinus chinensis var. chinensis, Fraxinus chinensis var. rhynchophylla and Manchurian ash, Fraxinus mandshurica. In Japan, the host range is somwhat broader and includes a subspecies of Manchurian ash, Fraxinus mandshurica var japonica, two subspecies of Manchurian walnut, Juglans mandshurica var. sieboldiana, and Juglans mandshurica var. sachalensis; Japanese wingnut, Pterocarya rhoifolia; Japanese elm, Ulmus davidiana var. japonica; and Chinese cork bark elm, Ulmus propinqua (Haack et al. 2002).

In North America, three species of ash have been reported as hosts: white ash, Fraxinus americana; green or red ash, Fraxinus pennsylvanica and black ash, Fraxinus nigra (Canadian Food Inspection Agency 2002, Haack et al. 2002).

      Agrilus planipennis is native to northeastern China (Jilin, Liaoning, Heilogjiang, Inner Mongolia, Hebei and Shandong Provinces, Taiwan, Korea, Mongolia, Japan (Hokkaido, Honshu, Kyushu and Shikoku) and the Russian Far East (Haack et al. 2002).
North America:
      This insect has become established in portions of Michigan and Ohio, U.S. and Ontario, Canada. It was first discovered in southeastern Michigan in 2002. As of September 11, 2002, emerald ash borer was found in six counties in Michigan (Livingston, Macomb, Monroe, Oakland, Washtenaw, and Wayne Counties), and Essex County in Ontario. By August 25, 2003, this insect had been detected in seven more counties in Michigan (Genesee, Ingham, Jackson, Lapeer, Lenawee, Shiawassee, and St. Clair) and two counties in Ohio (Lucas and Defiance). Infestations were detected in ash nursey stock in Maryland and Virginia in 2003 (USDA Forest Service 2003).
The genus Agrilus is a large genus of flatheaded woodborers with species found in Asia, Australia, Europe and North America (Browne 1968). The larvae typically feed in the cambium of trees or in the stems of vines and small woody plants. The adults are attractive insects with striking metallic colors and are often referred to as jewel beetles. Several species are of economic importance in forestry, arborculture and agriculture. About 100 species are native to North America. These include A. angelicus, a pest of ornamental oaks in California (Furniss and Carolin 1977) and the bronze birch borer, A. anxius, a pest of birches and a contributing factor to birch dieback, a condition which occurred over eastern Canada and the northeastern U.S. between 1930 and 1950 (Ciesla and Donaubauer 1994). The two-lined chestnut borer, A. bilineatus, attacks oaks in eastern North America (Drooz 1985, Haack and Acciavatti 1992) and is a contributing factor to North American oak decline (Ciesla and Donaubauer 1994). A. hyperici bores in the roots of St. John’s wort, Hypericum peforatum , an invasive weed, and has been introduced into portions of the western U.S. as a biological control agent (Krueger and Sheley 2002).

In China, Agrilus planipennis typically has one generation per year although some individuals may require two years to complete a generation. Adults are active between mid-May and July. After emergence, they walk to the crown of their host tree and feed on small amounts of foliage. They feed on foliage throughout their life. Initial flight begins 3-4 hours after the first feeding. They are active from 6:00 to 17:00 hours, and are especially active on warm, sunny days. On cloudy or rainy days, adults rest in bark cracks or on foliage and remain on foliage at night. Eggs are laid individually or in small groups on the bark surface, inside cracks and crevasses. Each female can lay between 68-90 eggs. Adult males typically live for 2 weeks and females for 3 weeks Eggs hatch in about one week. First instar larvae tunnel through the bark to the cambium, where they feed in from mid-June to mid-October. Larvae construct S-shaped galleries packed with frass, which increase in width as the larvae grow. The mature larvae overwinter in pupal cells. Pupation occurs in April and May. Individual larvae that are not full grown by autumn overwinter in the cambium, resume feeding in April and complete development in late summer. Adults remain under the bark for 1-2 weeks and then emerge through D-shaped exit holes that are about 3-4 mm wide (Chinese Academy of Science 1986, Haack et al. 2002, Yu 1992).

Studies conducted within the present area of infestation in North America suggest some subtle differences in the insect's biology. In North America, adults are active in August and can fly immediately after emergence. Adult activity occurs mostly during the afternoon hours (Haack et al. 2002).

Economic Impact:    Trees attacked by Agrilus planipennis are ultimately killed. In China, A. planipennis typically attacks ash trees that grow in open areas or at the edge of closed forests. However, entire stands can be killed during outbreaks. Attack densities are highest in the lower bole of host trees (Yu 1992).

In North America, on the other hand, Agrilus planipennis has infested and killed trees in both open settings and closed forests and attacks begin in the upper bole and main branches of host trees. Tree death usually occurs within three years following initial attack although heavier infestations can kill trees within 1-2 years (Haack et al. 2002).

Ash, the primary host of Agrilus planipennis, produces an attractive, high quality wood and is used for a variety of products including furniture, tool handles and baseball bats. Various species of ash are important components of many broadleaf forest communities, especially in eastern North America.

This insect is presently causing extensive mortality of ornamental and shade trees in southeastern Michigan, northeastern Ohio and Ontario, Canada. Ashes are important ornamental trees and can represent 5-20% of all street trees in communities the central U.S. and Canada. Loss of ash street trees could result in reduced values of urban homes. Moreover, homeowners in infested areas have fewer viable choices of suitable ornamental and shade trees (Haack et al. 2002).

Environmental Impact:   Extensive tree mortality could alter tree species composition of forests in favor of non-host species. Urban areas with significant populations of ash trees would be less attractive and susceptible to warming due to the loss of shade trees (Haack et al. 2002).

Control:    No effective control methods are currently available. However research is underway on evaluation of systemic insecticides, natural enemies, survival rates in cut trees etc.

Infested trees containing larvae and pupae can be cut and chipped. In North America, quarantines have been imposed by USDA and the Michican Department of Agriculture to restrict the movement of ash trees, firewood, branches and logs from infested to uninfested areas (USDA Forest Service 2003).

Symptoms:    Symptoms of attack include dieback and mortality of ash trees, frass filled larval galleries in the cambium, adult exit holes and the presence of insect life stages. Callus tissue produced by the tree in response to larval feeding may cause vertical splits 5 –10 cm in length to occur in the bark above a gallery (Canadian Food Inspection Agency 2002).

Morphology:    Adults are 8.5 - 14.0 mm long and 3.1 - 3.4 mm wide. The body is narrow and elongate, cuneiform, and is a beautiful metallic blue-green color. This species is glabrous (hairless), and is characterized by dense but fine sculpture. The head is flat and the vertex is shield-shaped. The compound eyes are kidney shaped and somewhat bronze colored. The prothorax is transversely rectangular and it is slightly wider than the head, but is the same width as the anterior margin of the elytra. The anterior margin of the elytra is raised forming a transverse ridge, the surface of which is covered with punctures. The posterior margins of the elytra are round and obtuse with small tooth-like knobby projections on the edge.

Eggs are white in color, turning to orange-brown before hatching. They are oval shaped, 1 x 0.6 mm in size. The center of each egg is slightly convex.

Mature larvae are 26 - 32 mm long and creamy white in color. The body is flat and broad. The head is small and brown and it is retracted into the prothorax, exposing only the mouthparts. The prothorax is enlarged, and the meso- and meta-thorax are slightly narrower. The mesothorax bears spiracles. The abdomen is 10-segmented. Segments 1 to 8 have one pair of spiracles each and the last segment bears one pair of brownish, pincer-like appendages (urogomphi).

Pupae are 10 -14 mm long and are creamy white in color. The antennae stretch back to the base of the elytra and the last few segments of the abdomen bend slightly ventrad (Canadian Food Inspection Agency 2002, Haack et at. 2002).

Testing Methods for Identification:    Examination of adults and/or larvae by a taxonomist with expertise in the family Bupresitdae is required for positive identification.

Research in China and Japan indicates that Agrilus planipennis adults are strong fliers and typically fly in 8 to 12 meter bursts. Long distance flights of more than 1 km. are also possible (Haack et al. 2002). Adults are small and subject to dispersal by air currents although they typically do not fly on windy days.

This insect can be transported in wood products containing bark strips moving via international trade. To date, at least six exotic species of Agrilus have become established in the U.S. Between 1985 and 2000, 38 confirmed interceptions of Agrilus spp. were made at U.S. ports of entry. Twenty-eight of these interceptions were from dunnage, 4 from crating, 4 from grape leaves, 1 from a cutting and one was at large in a ship’s hold (Haack et al. 2002).

Browne, F.G. 1968. Pest and diseases of forest plantation trees. Oxford: Clarendon Press, 1330 pp.
Canadian Food Inspection Agency 2002. Canadian Food Inspection Agency 2002. Agrilus planipennis Fairmaire, Emerald ash borer. Science Branch, On line: /sci/surv/data/agrplae.shtml
Chinese Academy of Science, Institute of Zoology 1986. Agrilus macropoli Oldenberger. In: Agriculture Insects of China (Part 1). Beijing: China Agriculture Press, pp. 445 (In Chinese, translated by Houping Liu and R. A. Haack).
Ciesla, W.M.; Donaubauer, E. 1994. Decline and dieback of trees and forests: A global overview. Rome, Italy: Food and Agriculture Organization of the United Nations, Forestry Paper 120, 90 pp.
Drooz, A.T., 1985. Insects of eastern forests. USDA Forest Service, Miscellaneous Publication 1426, 608 pp.
Furniss, R.L.; Carolin, V.M. 1977. Western forest insects. USDA Forest Service, Miscellaneous Publication 273, 654 pp.
Haack, R. A.; Jendek, E.; Houping Liu; Marchant, K.R.; Petrice, T.R; Poland, T.M.; Hui Ye 2002. The emerald ash borer: A new exotic pest in North America. Newsletter of the Michigan Entomological Society 47 (3-4): 1-5
Haack, R.A.; Acciavatti, R.E. 1992 . Twolined chestnut borer. USDA Forest Service, Forest Insect and Disease Leaflet 168, 10 pp.
Krueger, J.; Sheley, R. 2002 . St Johnswort (Hypericum perforatum). Montana State University, Extension Service, MT 199810AG, 4 pp.
Little, E.L. Jr. 1979. Check list of United States trees (Native and Naturalized). USDA Forest Service, Agriculture Handbook 541, 375 pp.
Ohio Department of Agriculture, 2003. Exotic pest confirmed in Ohio ash trees: State task force formed to determine course of action. Office of Communications, News Release dated February 28, 2003.
USDA Forest Service 2003. Emerald ash borer On line:
Yu, C. 1992. Agrilus marcopoli Obenberger. In: Forest Insects of China, 2nd Edition, Beijing: China Forestry Publishing House, pp 400-401 (In Chinese).
William M. Ciesla
Name and Address of the First Author:
William M. Ciesla
Forest Health Management International
2248 Shawnee Court
Fort Collins, CO
USA 80525
CREATION DATE:        06/23/03
MODIFICATION DATE:        06/23/03

Selected images from Forestry Images (
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Photo by David Cappaert,
Michigan State University


Mixed larval stages collected from single location on tree. Maybury State Park, Michigan; August 30, 2002
Photo by David Cappaert,
Michigan State University


Egg cluster. EAB eggs are deposited in July, singly or in small clusters in bark furrows.
Photo by David Cappaert,
Michigan State University


D shaped exit hole
Photo by David R. McKay,


infested firewood
Photo by Troy Kimoto,
Canadian Food Inspection Agency


Trunk injection - the wedgle is a syringe-like applicator, used here for injection of imidacloprid (Pointer) to control emerald ash borer.
Photo by David Cappaert,
Michigan State University