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Pest Alert: Asian Longhorned Beetle



Authors as Published

Authored by Eric Day, Extension Specialist, and Theresa A. Dellinger, Diagnostician, Dept. of Entomology, Virginia Tech


The Asian longhorned beetle (ALB; Anoplophora glabripennis) is not known to occur in Virginia. If it were to establish, ALB would threaten our street, backyard, and forest trees.

Adult Beetle Description

Adult ALB (Fig. 1) range in size from 25-37 mm (1-1.5”) in length. The banded antennae can measure over 70 mm (3”) long. ALB has a shiny black body with irregular white spots and blue tinted legs.

Figure 1, An adult Asian longhorned beetle with very long antennae rests on a tree trunk.
Figure 1. Asian longhorned beetle adult. USDA-APHIS

Egg and Larva

Female ALB lay 5-7 mm (0.25”) long eggs in shallow oviposition pits (Fig. 2) chewed in the bark. After hatching, the very small larvae bore into the tree. Full grown larvae (Fig. 3) can reach up to 50 mm (2”) long. ALB larvae are indistinguishable in appearance from the larvae of native roundheaded borers. Fully grown larvae pupate to the adult stage inside the host tree and then chew their way out.

Figure 2, Two shallow pits have been chewed into the bark of a tree with a quarter shown for size comparison.
Figure 2. Asian longhorned beetle oviposition or egg laying pits. Joe Boggs, The Ohio State University.
Figure 3, A stout beetle grub.
Figure 3. Asian longhorned beetle larva. Melody Keena, USDA Forest Service,

Host List

ALB has a wide host tree range in both Asia and the United States. Maple is the most common host and where ALB will likely have its biggest ecological impact. ALB also attacks birch, elm, golden raintree, London planetree/sycamore, horse chestnut/buckeye, mimosa, mountain ash, poplar, willow, ash, and katsura.


ALB adults emerge from large diameter exit holes in host trees when weather warms in the spring. (Fig. 4). Each hole is connected to a deep tunnel (Fig. 5) big enough to insert a pencil (Fig. 6), thus the pencil test is a good indicator of a possibly infested tree. After emergence, ALB females chew oviposition pits 10 mm (0.5”) in diameter where they lay eggs (Fig. 3). Initially the pit is light colored but darkens and may weep sap. Multiple exit holes and pits give trunks a spotted appearance (Fig. 4). Larvae tunnel initially in the cambium but later make large tunnels in the xylem (Fig. 5). Extensive large tunnels weaken the branch, causing them to break in strong winds.

Figure 4, A tree trunk with numerous holes and pits from insect activity.
Figure 4. Asian longhorned beetle exit holes and bark staining. Pennsylvania Department of Conservation and Natural Resources & Forestry,


ALB was first detected in 1996 in New York City. It has also been found in New Jersey, Illinois, Massachusetts, Ohio, South Carolina, and Ontario, Canada. Eradication efforts continue for infestations in Massachusetts, New York, Ohio, and South Carolina.

Figure 5, A crosscut section of a tree branch with several large tunnels created by insects.
Figure 5. Asian longhorned beetle tunneling, tree cross section. Joe Boggs, The Ohio State University
Figure 6, A pencil is deeply inserted into a large hole on the trunk of a tree.
Figure 6. Pencil test. Joe Boggs, The Ohio State University


Because many native insects resemble ALB, please capture suspect insects in case they need to be examined. Submit insect samples or photos of suspect damage to your Cooperative Extension office or County Forester.

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Publication Date

April 17, 2023