Asian Longhorned Beetle (ALB) Signs and Damage Pictures

The primary host trees for Asian longhorned beetle (ALB) are maple (Acer sp.), birch (Betula sp.), elm (Ulmus sp.), willow (Salix sp.), and horsechestnut (Aesculus sp.). Look for these signs year-round on those trees:

(click on images to enlarge)

The Bug:

The adult beetle is glossy black with distinct white splotches on the wing covers. It is between 1 and 1-1/2 inches long. It has very long antennae, at least the length of its body. It emerges from trees in July and can be seen until October.


Asian longhorned beetle adult female

An Asian longhorned adult female beetle (Photo by AP Photo/Telegram & Gazette, Christine Peterson)

native whitespotted sawyer adult female

NOT ALB! This is our native whitespotted sayer adult female beetle. Notice the white spot behind the "neck" (Photo by John F. Valo)

Oviposition Sites:

Round to oval pockmarks in the bark where an adult female has chewed a depression to lay an egg. One female lays up to 90 eggs, so many can be seen on a single tree.

more images

ALB exit holes and egg-laying pits

Exit holes and oviposition (egg-laying) sites (Photo by Dennis Haugen, USDA Forest Service)

heavily attacked tree

Oviposition (egg-laying) sites (Photo by Michael Bohne, USDA Forest Service)

Exit Holes:

Round holes 3/8 inch in diameter on the trunk or branches where the adult beetles emerge. A pencil can be inserted at least an inch into an ALB exit hole.

more images (Look for oviposition sites on the bark if you see a suspicious hole)

ALB exit hole with pencil

Exit hole (Photo by Rutgers University)

ALB exit holes

Exit holes (Photo by Kenneth R.Law, USDA APHIS PPQ)

Tunnels and Galleries:

Larval feeding tunnels meander towards the heartwood, where it will then pupate to complete development.

Look for these signs in split and cut wood.

ALB tunnels and pupal chambers

ALB larval tunneling and pupal chambers (Photo by Patricia Douglass, USDA APHIS PPQ)

ALB pupal chambers

Frass-filled pupal chambers (Photo by Joe Boggs,


Frass is sawdust-like material which the beetle larvae push out as it feeds in the tree. This may be found in oviposition sites, exit holes, branch junctions, or on the ground.


Frass coming out of oviposition site (Photo by Kenneth R.Law, USDA APHIS PPQ)

ALB and frass

ALB and frass on the ground (Photo by Michael Bohne, USDA Forest Service)


Updated: August 20, 2018