Keep an Eye Out: Asian Longhorned Beetle Closer to North Carolina than Ever Before

By on June 24, 2020

A 17-year cicada emergence, forest tent caterpillar outbreak, and global pandemic isn’t all that 2020 has to offer. On June 15th, Clemson University’s Department of Plant Industry and the U.S. Department of Agriculture announced that the Asian longhorned beetle, an invasive pest from China and Korea, was found in South Carolina for the first time. Only 120 miles from the state line, it is closer to North Carolina than ever before. Previously, the closest known infestation was in Ohio. Now more than ever, it is important to keep an eye out for and report this unwelcome tree-killer and reduce its spread by not moving firewood.

The Asian longhorned beetle is distinctive in its color pattern and can be detected by several signs, such as its perfectly round exit hole shown to the left. Image: Kenneth R. Law, USDA APHIS PPQ, Bugwood.org.

The Asian longhorned beetle, Anoplophora glabripennis, was first found attacking ornamental trees in the United States in New York in 1996. It likely entered the U.S. through untreated wooden packaging crates from China. Since then, it has spread to Illinois, Massachusetts, New Jersey, Ohio, and, most recently, South Carolina. In the U.S., it is known to attack 29 species of hardwood trees! It prefers maple/boxelder (Acer), but other known hosts include birch (Betula), willow (Salix), elm (Ulmus), horsechestnut/buckeye (Aesculus), mimosa (Albizia), ash (Fraxinus), and poplar (Populus).

The Asian longhorned beetle is potentially the most devastating invasive pest to reach North America. It could cause more damage than Dutch elm disease, chestnut blight, and gypsy moth combined! The beetle can destroy millions of acres of hardwood trees, putting forest ecosystems and industries in danger and causing billions of dollars in damage to the lumber, nursery, and tourism industries.

While the preferred host is maple, the Asian longhorned beetle is destructive to many species of hardwood trees. It can cause branch breakage, dieback, and early fall coloration as the immature forms feed on tissues of the trees. Image: Dennis Haugen, USDA Forest Service, Bugwood.org.

As the larvae of Asian longhorned beetle feed on tissues of trees underneath the bark, they disrupt the flow of nutrients within the tree, causing breakage, dieback, and eventually death. As they grow, these hungry grubs venture into the woody tree tissue and continue to form tunnels as they grow. Once adults exit the tree, they feed on the bark and leaves, further harming it. Clearly, it is important that North Carolinians keep their eyes peeled for this striking yet destructive pest and its signs to prevent it from establishing in our state.

While somewhat distinctive in appearance, there are a few native insects that could be confused with this tree-killer. The whitespotted pine sawyer is the most similar-looking insect to the Asian longhorned beetle in N.C. The native sawyer is mottled brown or metallic black in color with faintly banded antennae. It can be distinguished by the white spot in the center of the wing covers, behind the head (this spot is not present on the Asian longhorned beetle). Sawyer beetles are common and attack stressed or dying pines and other conifers. The Asian longhorned beetle may also be confused with the eyed click beetle which is 1 – 1¾ inch long with white speckles and black “eye spots”. It is a predator of many wood-boring insects and is not considered a pest. So, if you’re searching for the Asian longhorned beetle, don’t get confused by its harmless look-a-likes!

The Asian longhorned beetle has a few look-a-likes, including the native whitespotted sawyer, which is not considered a pest. The whitespotted sawyer has a white spot directly behind the head that the Asian longhorned beetle lacks. Image: Maine Forest Service, maine.gov.

The Asian longhorned beetle leaves behind several clues after attacking a tree. The most distinctive is its perfectly round exit holes, which are about the width of a standard pencil eraser. When laying eggs, female beetles create a pit in the bark where they deposit a single egg. These pits are another sign that Asian longhorned beetle is present, along with the sap that may seep from the egg-laying spots. Other signs and symptoms include frass (excrement that looks like sawdust), bark cracking, branch breakage, and early fall coloration.

Management of the Asian longhorned beetle is not very pretty. Early detection and rapid response is the best way to eradicate the Asian longhorned beetle within a region. Removing and destroying all infested trees is necessary to rid an area of the pest. Even though this is not the most desirable technique, it is one that works. It has proven effective in states like Illinois and New Jersey where the pest has been eradicated.

To prevent the destruction of North Carolina’s hardwood trees, it is important that residents can recognize the signs and symptoms of the Asian longhorned beetle. Since the beetle spreads through wood, one of the best ways to prevent it is to buy and burn local firewood. Many invasive species, including the Asian longhorned beetle, can hitch a ride inside traveling firewood, so avoiding moving firewood long distances is a great way to reduce their spread. By remaining aware and reporting any sightings to the N.C. Forest Service, North Carolinians can ensure our hardwoods are protected – as long as the Asian longhorned beetle’s look-a-likes don’t play any tricks!

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