The Asian longhorned beetle (ALB) is a large, striking insect that is black with white spots, 1 to 1 ½” long, has long black and white striped antennae and bluish feet. This beetle is in the family Cerambycidae and is originally from China and the Koreas. First found in New York in 1996, established populations in the U.S. can be found in New York, Massachusetts, and Ohio. A population of ALB was confirmed in Charleston County, South Carolina in June 2020.
Several large longhorned beetle species live in SC, of which the cottonwood borer (Plectrodera scalator) is most commonly confused for ALB. This insect is slightly larger than ALB (it can be ~2” long), is predominantly white with black spots, lacks the blueish feet, and has solid black antennae. The whitespotted sawyer is another large longhorned beetle found in SC, but lacks white spots on the antennae and does not have bluish feet. Several large longhorned beetles, commonly known as prionids, may be confused with ALB, but these beetles are brown – not black – and lack white spots on their body and antennae.
Biology and Damage
ALB adults generally emerge from host trees in late spring and summer. Adults chew large round holes in the tree through which they emerge. Adults mate and feed on twigs and green bark, after which females chew a concave depression in the bark and deposit a single egg. Larvae hatch in about two weeks and chew into the tree, feeding on the phloem and eventually making their way into the xylem, where they will feed until ready to pupate. This feeding causes large galleries in the tree, weakening it and making it susceptible to breaking. Larvae pupate in the wood, and adults emerge the following year.
ALB has a broad host range and will feed on trees in 12 different genera, including several tree species present in SC. Maples (Acer spp.), elms (Ulmus spp.), birches (Betula spp.), and willows (Salix spp.) are preferred hosts. Other tree genera less commonly recorded as hosts include planetrees (Platanus spp.), poplars (Populus spp.), horse chestnuts and buckeyes (Aesculus spp.), mimosa tree (Albizia julibrissin), katsura tree (Cercidiphyllum japonicum), golden raintree (Koelreuteria paniculata), and mountain ash (Sorbus spp.). Many of these trees can be found in natural and managed landscapes across SC. Ash trees (Fraxinus spp.) can also be hosts for ALB and are already threatened by the emerald ash borer (Agrilus planipennis).
All host trees can be found in managed and natural landscapes; some are very common in yards, public areas, and other urban environments. An infestation of these trees will not only damage or kill the tree, but the weakening caused by larval tunneling can create a hazard for breaking branches.
Prevention is the most effective management tactic. Once a tree is infested with ALB, there is little that can be done other than removing the tree. Removed trees should be chipped or burned on-site, as it is possible to move ALB long distances in pieces of wood (e.g., firewood). While contact insecticides will kill adults, their relatively short time outside the tree makes this management strategy ineffective. Once larvae are inside the tree insecticides will not work.
USDA APHIS and Clemson DPI are working on managing the current infestation in SC. If you think you see an ALB, please capture the insect or take a photo and contact the Clemson Department of Plant Industry ALB Program (firstname.lastname@example.org or by calling 843-973-8329) or your local Clemson Extension office, which can be found here: https://www.clemson.edu/extension/co/index.html.
Additional ALB resources include the USDA APHIS webpage: AsianLonghornedBeetle.com