Agrilus planipennis

Fairmaire, 1888

Emerald Ash Borer, EAB

Agrilus planipennis, the emerald ash borer, is a highly destructive native to northeastern Asia. First detected in North America in 2002 (Michigan) and European Russia in 2003, it has since spread to 36 U.S. states, five Canadian provinces, and across Eastern Europe. The has killed hundreds of millions of ash trees, causing severe ecological and economic damage. In its native range, it occurs at low densities without significant tree mortality; in invaded regions, it typically kills over 90% of ash trees within 2–4 years of establishment.

Agrilus planipennis by (c) Benjamin Smith, some rights reserved (CC BY), uploaded by Benjamin Smith. Used under a CC-BY license.

Agrilus planipennis oviposition by Wang, et al.. Used under a CC BY 3.0 license.

Agrilus planipennis 001 by Pennsylvania Department of Conservation and Natural Resources - Forestry Archive. Used under a CC BY 3.0 us license.

Pronunciation

How to pronounce Agrilus planipennis: /əˈɡraɪləs plænɪˈpɛnɪs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

are metallic emerald-green beetles approximately 8.5–13.5 mm long with elongated bodies. Larvae create distinctive S-shaped galleries beneath bark. D-shaped exit holes (approximately 3–4 mm) are left by emerging adults. Crown thinning, epicormic sprouting, and bark splits are visible of . Adults are difficult to detect directly due to their -dwelling and brief activity period.

Images

Habitat

Associated with ash trees (Fraxinus spp.) in forested areas, urban plantings, parks, and streetscapes. In North America, often first appear near transportation corridors—roads, railways, and automobile terminals—due to human-assisted . The shows preference for open-grown and stressed trees, and larger trees with existing dieback.

Distribution

Native to northeastern Asia (China, Japan, Korea, Mongolia, Taiwan, Russian Far East). in North America: detected 2002 in Michigan, now present in 36 U.S. states and five Canadian provinces; recently detected in Oregon (2024). In Europe: established in European Russia since 2003, spreading westward through Ukraine (detected 2019) and into Central Europe; detected in Altai region of southern Siberia (2024).

Seasonality

emerge from May to July in temperate regions, peaking in June. One typically occurs per year in most of its range, though two-year generation time has been documented in cooler regions (e.g., Barnaul, Russia). Larval development occurs beneath bark throughout the growing season.

Diet

Larvae feed on phloem and outer sapwood of ash trees (Fraxinus spp.), creating galleries that girdle and kill trees. feed on ash foliage, with notching visible on leaflets; maturation feeding on foliage is required before .

Host Associations

Fraxinus pennsylvanica - primary strongly preferred in North America
Fraxinus excelsior - European ash; significant damage documented in Russia
Fraxinus americana - white ash
Fraxinus mandschurica - Manchurian ash; native range
Chionanthus virginicus - secondary white fringetree; confirmed since 2014, though trees in low- ornamental settings often survive
Osmanthus americanus - marginal devilwood; limited larval survival demonstrated in laboratory

Life Cycle

are deposited in bark crevices. Larvae hatch and tunnel into phloem, progressing through four instars while creating S-shaped galleries. occurs in spring in outer bark or sapwood. emerge through D-shaped exit holes. time is typically one year, though two-year development occurs in cooler climates.

Behavior

are strong fliers active in tree , making them difficult to observe directly. Males are attracted to female-produced macrocyclic lactone (3Z)-12-dodecenolide combined with . Larval feeding is cryptic, occurring entirely beneath bark, which delays detection until trees show visible decline.

Ecological Role

In native Asia, a minor component of forest with natural enemy regulation. In invaded regions, a keystone pest causing cascading ecosystem effects: loss of ash-dominated forest , altered nutrient cycling, and impacts on dependent on ash (e.g., specialized arthropods, birds). Dead ash trees create hazardous fuel loads and change forest structure.

Human Relevance

One of the most economically damaging forest insects in North America. Management costs include tree removal, replacement, and chemical protection; estimated costs exceed $10 billion by 2019. on firewood and ash materials are primary regulatory responses. using introduced (Spathius galinae, Tetrastichus planipennisi, Oobius agrili) is widely implemented. Detection methods include -baited traps and surveillance using the predatory wasp Cerceris fumipennis, which provisions nests with buprestid beetles.

Similar Taxa

Agrilus obsoletoguttatussympatric buprestid in North America; distinguished by different associations and gallery patterns
Other Agrilus speciesnumerous congeneric exist; identification requires examination of genitalia or molecular methods