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Asian and citrus longhorned beetles
Asian longhorned beetle
Asian longhorned beetle
Asian longhorned beetle (Anoplophora glabripennis) and Citrus longhorned beetle (A. chinensis)

The Asian longhorned beetle (ALB), (Coleoptera: Cerambycidae), and the citrus longhorned beetle (CLHB), Anoplophora chinensis are both native to Asia. ALB and CLHB larvae are longhorned wood borers that feed in both the sapwood and heartwood in a wide variety of hardwood trees. Unlike most longhorned beetles, they are serious pests because they can attack and kill healthy trees (Figure 1). ALB most commonly attacks maples, willows, birch, elm, and horsechestnut. CLHB is a known pest of citrus (hence the name), but also apple, poplar, and willow with a known host range of over 100 tree and shrub species.

ALB adult
Figure 1. ALB adult and tree damage
ALB is regularly found with shipments containing solid wood packing material from Asia. Infestations of cargo in warehouses have been discovered and destroyed in at least 17 states including Alabama, California, Florida, Georgia, Indiana, Maine, Massachusetts, Michigan, New Jersey, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, Texas, Washington, and Wisconsin, as well as in Canada in British Columbia, Manitoba, Ontario, Quebec, and Nova Scotia.

ALB was first found in North America in New York in mature maple and horse chestnut trees in 1996. Established populations of ALB have been found in Illinois, Massachusetts, New Jersey, New York, and Toronto, Canada. The populations in Illinois and New Jersey have been declared eradicated. The most recently discovered infested state is Massachusetts in Worcester County during 2008 and Boston in 2010. Eradication programs, including removal and destruction of all infested trees, are in progress in infested states.

CLHB was first intercepted in the US in 1908 at a nursery in San Francisco, California. More recently, it has been detected in shipments to Georgia and Wisconsin. They did not have opportunity to become established. An eradication was performed for CLHB around a Washington nursery in 2001 after the adults emerged from bonsai. CLHB has not been detected in the area since. In spite of suggestions that CLHB is not cold tolerant, CLHB is apparently able to overwinter in cold climates as an established population was detected overwintering in the Netherlands.

Since 1997, every year with the exception of 2008, a visual survey for ALB and CLHB in Oregon has been conducted to detect any early infestations of these pests. No ALB or CLHB have been detected.

Identification of adults
ALB and Oregon natives
Fig 2. ALB is at top of photo with Oregon natives underneath
Adult ALB and CLHB are very similar, and it is difficult to tell the two apart. Although neither are likely to be seen, they are large (about ¾ to 1 1/4 inches long), black with white spots, and very glossy. ALHB is called the "starry night" beetle in China due to its coloration. The antennae are longer than the beetle's body and are banded black-and-white. Adults may be crawling over the trunks and branches of host trees, or possibly flying. There are several Oregon native beetles which are roughly the same size and color as ALB and CLHB (Figure 2), so any suspicious beetles should be captured if at all possible and placed in a jar or film canister (NOT plastic bags - they'll chew through!). Include a label that includes the address and date inside the container and promptly notify the Oregon Department of Agriculture.
It is worth noting that worldwide there are 36 species in the Genus Anoplophora. Future changes in forestry practices or commerce could lead to their introduction to North America through the movement of wood products. Many of them look similar to ALB and CLHB, but there is wide variety in colors (blues, reds, and yellows) and in the patterns on the wing covers. To be safe , report any suspicious longhorned beetles to the Oregon Department of Agriculture.

Identification of ALB damage
beetle emergence holes
Figure 3. Beetle emergence holes

  • Large (about 3/8" or 1cm in diameter), perfectly ROUND emergence holes (Figure 3) where adult ALHB/CLHB have emerged from the tree. A good quick-and-dirty way to tell whether holes are the right size is whether a pencil fits into a hole. If not, the hole is too small to have been caused by ALHB/CLHB.

  • Oval-to-round wounds or scars on the bark (Figure 4) where female ALHB/CLHB have chewed out a place to lay eggs. The wounds are pale when fresh but darken with age. Sap flows and stains are often associated with egg laying scars. These scars are about 3/8" (1 cm) long and may occur in a row with about 3 - 5" (7.6 to 12.7 cm) between scars.

egg laying scar
Figure 4. Egg laying scar on tree trunk.
  • "Sawdust" is caused by adult beetles chewing their way out from inside the tree. It is often found around the base of trees or where branches meet the main stem (Figure 5).

Figure 5. "Sawdust" caused by adult chewing damage.
  • Heavy sap flows running down trunks and branches. These flow from egg-laying sites due to larval feeding.
  • “Flagging” is wilting or browning leaves at branch tips or dead twigs or branches and is a result of the damage to the tree’s vascular tissue by the boring larvae.
Damage caused by native species can often be mistaken for ALHB damage and be reported. Some native carpenterworms and wood-boring beetles prefer the dead wood of tree scars and wounds. This type of damage is normally confined to the exposed dead wood. Holes made by woodpeckers searching for grubs under bark are also frequently reported. These holes are often in neat rows and are too small for ALHB/CLHB. They also do not extend very deep into the wood, unlike ALHB or other wood-boring beetle emergence holes. Native wood-boring beetles also use many of the same trees preferred by ALHB/CLHB, but their emergence holes are generally smaller and are often only in dead or rotting wood. ALHB and CLHB prefer healthy trees and sound wood.

IMPORTANT: We´d much rather you report damage caused by non-ALHB or CLHB than risk missing an actual infestation!

Preferred hosts

The following are the preferred hosts of ALHB:
All native and ornamental maples (including Norway, boxelder, big leaf, silver, sugar, vine and Japanese maples), willows, elm, and horsechestnut are the trees most commonly attacked, but birch, poplar, silk tree, sycamore, ash, and mountain ash are also hosts.
CLHB attacks many of the same hosts as ALHB but apparently prefers citrus, apple, poplars and willow.  Interceptions in the US have been in maple and crepe myrtle.


What can you do?

If you see ALHB or CLHB: Capture the beetle and place it in a jar or other hard sided container (not a plastic bag, as it will chew its way out).  Immediately report the information by calling the Oregon Department of Agriculture at: (503) 986-4636 or 1-800-525-0137.

Other sites of interest

Figure 1.  E. Richard Hoebeke, Cornell University, Bugwood.org
Figure 2.  Image of three beetles on current webpage
Figure 3.  Emergence hole.  Units in inches.  Dennis Haugen, USDA Forest Service, Bugwood.org
Figure 4.  Wound where female lays her eggs.  Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org
Figure 5.  Boring dust from beetle emergence.  Roberta A. Haack, USDA Forest Service, Bugwood.org