Asian longhorned beetle

What is Asian longhorned beetle?

Asian longhorned beetle is a wood-boring beetle native to Asia. It most likely reached the US in wood packing material, and was first found in Brooklyn in 1996. The larvae tunnel through the inner bark and deep into the wood of maples and other hardwoods.

Repeated attacks can girdle and kill a tree within several years, and limbs can fall from trees that still look healthy. APHIS says there is no cure once a tree is infested because the larvae feed deep in the wood where treatments can't reach. Homeowners aren't expected to manage it themselves; APHIS and its partners find infested trees and remove them, then burn or chip the wood, to wipe the beetle out.

Infested wood can carry the beetle to new places. That is why APHIS regulates hardwood firewood, logs, stumps and branches in quarantine areas, and why NC State advises using heat-treated or kiln-dried firewood when moving it. APHIS asks everyone to spend about 10 minutes checking their trees each August, which it calls Tree Check Month.

Plants it attacks: maples (most preferred; red maple in South Carolina), birch, horsechestnut and buckeye, poplar, willow, elm, ash, golden raintree, mimosa, mountain ash, katsura, sycamore and London planetree.

Signs and damage

• Round exit holes about 3/8 inch across, about the size of a dime, in trunks and branches
• Oval or round chewed pits in the bark where eggs were laid, sometimes oozing or foaming sap
• Sawdust-like frass at the tree base or caught in branch forks
• Branch dieback, limbs breaking off healthy-looking trees, and leaves yellowing early

Asian longhorned beetle identification: what to look for

• Adult: Shiny black with white spots, about 3/4 to 1 1/2 inches long. Long antennae with alternating white and black bands. Feet can look blue.
• Larva: Cream-colored, legless, segmented, with dark mouthparts, up to about 2 inches long. Lives inside the wood and is rarely seen.
• Eggs: White to cream, about the size of a grain of rice, laid one at a time in chewed bark pits.
• Damage: Round exit holes about 3/8 inch, egg pits 1/2 to 3/4 inch, sawdust-like frass, tunnels in the wood, dieback and broken limbs.
• Timing: In Massachusetts adults start coming out around July 1 and may be active into late fall. Exit holes can be found year-round.

Life cycle

Females chew pits in the bark and lay one egg in each. Larvae hatch in about two weeks and tunnel under the bark, then deeper into the wood, where they spend the winter. After one or two seasons inside the tree they pupate in late spring, and adults chew out through round exit holes several weeks later. The full cycle takes one to two years depending on temperature.

When to look: Adults are most active in summer and early fall (from about July 1 in Massachusetts). APHIS suggests checking trees in August. Exit holes, egg pits and frass can be found any time of year.

Asian longhorned beetle look-alikes

A few things get mixed up with it:

• Whitespotted sawyer (Monochamus scutellatus): A pine sawyer beetle. NC State says pine sawyers have long antennae but are much smaller and lack ALB's bold black-and-white pattern; the whitespotted sawyer has a single white spot at the base of the wing covers.
• Cottonwood borer (Plectrodera scalator): Also big with black and white markings, but it has much more white, and its antennae are not banded black and white.

How to control Asian longhorned beetle

Cultural control

• Use heat-treated or kiln-dried firewood when moving it, or burn untreated firewood within 50 miles of where it was cut (NC State).
• Follow quarantine rules on firewood, logs, stumps, branches and nursery stock in regulated areas.
• Monitoring and reporting are the main tools for homeowners; APHIS says infested trees must be removed.

Chemical control

UMass Extension lists no chemical control and says monitoring and reporting are the only recommended steps. APHIS says there is no cure once a tree is infested because larvae feed deep in the wood. In quarantine areas APHIS and its partners handle eradication, including removing and chipping infested trees. Don't try to treat a suspected ALB tree yourself; report it. If any pesticide is ever used on trees for other pests, use only products labeled for this use; the label is the law, and the work belongs to an ISA Certified Arborist or licensed applicator (see our pesticide applicator license guide). Muthler Landscaping does not treat trees or apply pesticides.

Use only products labeled for this pest and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Don't move firewood; see our firewood rules guide.
• Check maples and other host trees for round exit holes and egg pits.
• Report any suspect beetle or damage with photos.

When to call a pro

Report first. If an infested or suspect tree needs removal outside an APHIS program, use an ISA Certified Arborist and follow quarantine rules for the wood.

Related guides: Tree database: mature size and planting distance · Pennsylvania tree identification · Firewood rules by state · All pests and diseases

Questions about Asian longhorned beetle

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