Agrilus planipennis (Emerald ash borer) - Fact Sheet

Identification

Adult beetles are metallic blue-green, narrow, hairless, elongate, 8.5 to 14.0 mm long and 3.1 to 3.4 mm wide.Footnote 1 The head is flat and the vertex is shield-shaped.Footnote 1 The eyes are bronze or black and kidney shaped.Footnote 1 The prothorax is slightly wider than the head and is transversely rectangular, but is the same width as the anterior margin of the elytra. The posterior margins of the elytra are round and obtuse with small tooth-like projections on the edge.Footnote 1

Mature larvae are 26 to 32 mm long and creamy white.Footnote 1 The body is flat and broad shaped.Footnote 1 The posterior ends of some segments are bell-shaped. The abdomen is 10-segmented. The 1st 8 segments each have one pair of spiracles and the last segment has one pair of brownish, pincer-like appendages.Footnote 1

Plant Pest Credit Card- Emerald ash borer PDF (1.3 mb)

Host Trees

Fraxinus, Juglans, Pterocarya and Ulmus.Footnote 1 In North America, only Fraxinus has been found infested to date.

Location of Infestation within the Tree

Larvae feed on the inner bark and sapwood along the entire bole and larger branches (greater than 2.5 cm diameter) in the crown. In addition to mature trees, galleries can occur in young saplings. Immature beetles maturation feed on leaves.Footnote 1

Host Condition

Healthy or weakened trees.Footnote 1

Distribution

China, Japan, North Korea, South Korea, Mongolia, Russia and Taiwan.Footnote 1

Introduced to Canada: For current distribution information, please see the main Emerald Ash Borer page on the CFIA web site.

Introduced to USA: For current distribution information, please see the main Emerald Ash Borer page on the United States Department of Agriculture's Animal and Plant Health Inspection Service (USDA-APHIS) website.

Signs and Symptoms

Immature beetles maturation feed on host tree foliage, creating irregular notches in the leaves.Footnote 1 Eggs are laid singly on the bole or branches.Footnote 1 First instar larvae bore through the bark and feed on the inner bark and the outer sapwood, eventually forming flat and wide (6 mm), "S-shaped" galleries that are filled with a fine brownish frass.Footnote 1 Galleries are 9 to 16 cm long (up to 20 to 30 cm) and increase in width from the beginning to the end.Footnote 1 Galleries can occur along the entire bole and in branches that are at least 2.5 cm in diameter.Footnote 1 Callus tissue may be produced by the tree in response to larval feeding and may cause vertical bark cracks to occur over a gallery.Footnote 1

Pupation takes place at the end of a gallery just beneath the bark, or near the surface of the sapwood (5 to 10 mm) and even in the corky tissue of thick-barked trees.Footnote 1 Beetles emerge through "D-shaped" exit holes, 3.5 by 4.1 mm in size.Footnote 1 These holes are very difficult to find so careful inspection is required.Footnote 1 Woodpecker activity may also indicate the presence of this beetle.Footnote 1 Dying or dead trees, particularly with bark sloughing off and crown die-back can also be used as indicators of attack.Footnote 1 Other signs of attack include a thinning crown, epicormic shoots, and vertical cracks on the trunk.Footnote 1

Adult Agrilus planipennis (8.5-14 millimetre long). Metallic, green-blue body.
A - Adult A. planipennis (8.5-14 mm long). Metallic, green-blue body.
Various larval instars of Agrilus planipennis.
B - Various larval instars of A. planipennis.
S-shaped larval galleries of Agrilus planipennis.
C - S-shaped larval galleries of A. planipennis.
D-shaped exit hole (3.5 by 4.1 millimetre) of Agrilus planipennis.
D - D-shaped exit hole (3.5 by 4.1 mm) of A. planipennis.
Epicormic shoots caused by Agrilus planipennis.
E - Epicormic shoots caused by A. planipennis.
Vertical bark cracks over larval galleries caused by callus tissue production.
F - Vertical bark cracks over larval galleries caused by callus tissue production.
Thinned ash crowns infested with Agrilus planipennis.
G - Thinned ash crowns infested with A. planipennis.

Photo credits

  • A David Cappaert, Michigan State University, Image 9000019, www.invasive.org, Feb. 5, 2004
  • B David Cappaert, Michigan State University, Image 1460072, www.invasive.org, Mar. 6, 2003
  • C David Cappaert, Michigan State University, Image 1460075, www.invasive.org, April 1, 2004
  • D Jerry Dowding, Canadian Food Inspection Agency
  • E Ed Czerwinski, Ontario Ministry of Natural Resources, Image 1439003, www.invasive.org, Mar. 6, 2003
  • F Jerry Dowding, Canadian Food Inspection Agency
  • G Jerry Dowding, Canadian Food Inspection Agency
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