Asian longhorned beetle, Anoplophora glabripennis
Order: Coleoptera
Family: Cerambycidae
Description
The Asian longhorned beetle (ALB) is a species of wood-boring beetle that is native to China and other parts of Asia. It is considered an invasive species in urban areas of the United States and was initially detected in 1996 in New York but has not been reported in Colorado. Eradication efforts have been successful in various cities, most notably Chicago, IL, and early identification in Colorado will likely improve the probability of eradication. A wide variety of trees in the United States are susceptible to attack by ALB, including ash (Fraxinus spp.), birch (Betula spp.), elm (Ulmus spp.), goldenrain tree (Koelreuteria spp.), sycamore (Platanus spp.), maple (Acer spp.), horsechestnut (Aesculcus spp.), katsura (Cercidiphyllum spp.), mimosa (Albizia spp.), mountain ash (Sorbus spp.), poplar (Populus spp.), and willow (Salix spp.). However, based on observations made in Illinois and New York, ALB is most likely to infest various species of maple, horsechestnut, willow, and American elm (U. americana). In the United States, ALB has been documented in trees as small as 8 cm (3.2 inches) in diameter.
Adults are large beetles that measure 1.9-3.2 cm (3/4 – 1 1/4 inches) in length. The glossy black body is covered with irregular white spots. The antennae have 11 segments, are very long (sometimes over twice the body length) and are black with alternating black and white bands. Initial reports of ALB are often brought to the attention of government officials by members of the public. Several beetle species in Colorado may be confused with adults of ALB, such as the cottonwood borer (Plectrodera scalator), spotted pine sawyer (Monochamus mutator), whitespotted sawyer (Monochamus scutellatus), Prionus spp., and Trichocnemis neomexicanus. A detailed description for each of these beetle species is available here.
The eggs of EAB measure about 5-7 mm (~1/5 inch) and are about the size of a large grain of rice. The cream-colored larvae are the damaging life stage and reside within the host tree. The larvae are legless, have a brown head capsule with heavily sclerotized black mandibles, and can grow up to 5 cm (2 inches) long when mature. It should be noted that the larvae of certain wood-boring beetles in Colorado have similar morphology and are not easily distinguishable from the larvae of ALB. Pupae of ALB are cream-colored and have certain morphological features seen on adults, such as darkening eyes and developing legs and antennae.
Findings can be reported to the Colorado Department of Agriculture, or emailed to CAPS.program@state.co.us. To aid in identification, submitting photos of the insect in question is highly recommended.
Quick Facts
- Asian longhorned beetle (ALB) poses a significant threat to America’s hardwood trees due to its high adaptability to a different climatic condition and broad host range, which includes many common landscape trees such as maples (Acer spp.), poplars (Populus spp.), ash (Fraxinus spp.), elms (Ulmus spp.), and willows (Salix spp.). Currently, this pest is known to occur in urban areas of the eastern and midwestern United States and was more recently discovered in South Carolina. However, it has not been reported in Colorado.
- Juvenile stages can reside in firewood, wood packing material, wood debris and trimmings, branches, logs, stumps, and lumber. Transporting such materials can facilitate the spread of ALB.
- When an infestation is confirmed in the United States, eradication efforts involve establishing a quarantine zone, restricting the movement of wood-based materials out of the quarantine zone, removal of infested trees in the area, and the application of an insecticide to protect healthy trees. It is important to note that early identification is necessary for successful eradication.
- It is difficult to distinguish between the feeding injuries produced by ALB and those of other wood-boring cerambycid beetles. Therefore, it is recommended that individuals focus on identifying adults of ALB, which are relatively large and have distinct morphological features that distinguish them from other wood-boring cerambycid beetles inhabiting Colorado.
Adult Asian longhorned beetle. Note the black body with white spots and very long antennae with alternating black and white bands. Image credit: Kenneth R. Law, USDA APHIS PPQ, Bugwood.org
Larva of ALB. Note the absence of legs and brown head capsule with dark mandibles. Image credit: USDA APHIS PPQ – Oxford, North Carolina, USDA APHIS PPQ, Bugwood.org
Eggs of ALB. Image credit: Melody Keena, USDA Forest Service, Bugwood.org
Exit hole produced by ALB. Image credit: USDA APHIS PPQ – Oxford, North Carolina , USDA APHIS PPQ, Bugwood.org
Life history
Asian longhorned beetle can overwinter as eggs or pupae in the bark of a host tree. The following spring or summer, adults emerge and can remain active through early fall. Adults feed on leaf petioles and can also debark small branches to feed on the cambium. The beetles are most active later in the day and tend to remain on their natal host but can fly several hundred meters in search of a suitable host when the natal tree is in declining health. The emission of volatile organic compounds by potential host trees plays an important role in cerambycid beetle host selection and reproduction.
Eggs are laid singly near the bark surface in shallow pits chewed by the mother, and a single female can produce well over 100 eggs throughout her life. Oviposition occurs in areas where the bark is relatively thin, especially the crown of a host tree near the main branches during the early stages of an infestation and can also occur on the trunk of heavily infested trees. After about two weeks, the egg hatches and the newly emerged larva begins tunnelling into the tree where it feeds on plant tissues that facilitate nutrient transport and the production of new growth. Although many larvae can develop in a single host tree, the larvae of ALB are solitary and tend to form galleries that do not merge. As larvae feed, they develop through five instars that gradually increase in size with each molt. Depending on temperature, larvae can take 1-2 years to mature, at which point they chew a pupation chamber in the sapwood. Pupal development can take 12-50 days, with colder temperatures promoting longer development times. In the eastern United States, ALB produces one generation every two years.
Injury
The initial attacks of ALB tend to be concentrated on areas of the branches and upper canopy where the bark is thin. As the population builds, females lay eggs on lower branches, and eventually the trunk. Sap is often observed oozing from oviposition sites on bark, which are initially red or light brown and gradually darken as they weather. The oviposition pits can appear as narrow slits that are under 1 mm in height, to an irregular oval-shaped pit that measures up to 15 mm (3/5 inch) in diameter. The exit holes produced by ALB are round and have a diameter of 6-18 mm (1/4-7/10 inch). Based on observations in China and Chicago, adults often attack trees near the crown base of the upper trunk and lower parts of branches. Feeding of larvae produces meandering tunnels through the sapwood and heartwood, which disrupts the host’s nutrient transport mechanism and can lead to dropping branches and tree mortality. However, healthy trees can harbor infestations without immediately displaying any clear symptoms. While other species of wood-boring cerambycid beetles produce similar feeding injuries, they generally create smaller exit holes when compared with the exit holes of ALB.
Monitoring
In areas with confirmed infestations of ALB, visual surveys are conducted on susceptible trees within a 0.5-mile radius of each infestation point. Susceptible trees are inspected for the presence of exit holes, the accumulation of frass at the base of the host tree, and sap flowing from bark wounds. The use of binoculars, spotting scopes, and bucket trucks can aid in detecting early infestations, which tend to be concentrated in the upper portions of the tree. Once an infestation is confirmed, host trees are felled, destroyed, and often replaced with non-host trees. However, since these injuries are also produced by other wood-boring cerambycid beetles in Colorado, detecting new infestations of ALB requires public participation in searching for and reporting adults.
Prevention
Planting trees that are well-adapted to local conditions is recommended, as healthy trees are less susceptible to attack by wood-boring beetles. Proper cultural care, pruning, and removing dead or dying trees is also recommended. Freshly cut wood should not be stored near potential host trees.
Cultural control
Destroying heavily infested trees and replacing susceptible trees with resistant varieties have been a major approach to controlling ALB in China. Although these methods are labor intensive and costly, these practices help maintain populations of ALB below pest thresholds, especially in urban areas and young trees.
Eradication
Eradication efforts in the United States have been successful and involve establishing quarantine zones that restrict the movement of wood, destroying all infested host trees, and the application imidacloprid via a soil or trunk injection to all healthy trees in the quarantined area to protect them from feeding of ALB adults or larvae. Infested trees generally cannot be saved with insecticides, and any trees harboring ALB are removed to limit growth of the pest population. In addition to insecticides, bands containing conidia of entomopathogenic fungi can be deployed on the trunk of susceptible trees. Beetles become infected as they walk over the surface of these bands, which reduces their oviposition rates and eventually kills them.
Before committing to chemical controls, government officials evaluate potential environmental impacts, the scale of the ALB infestation, and cost of treating the area. It is worth noting that imidacloprid applications can help suppress the ALB population but may not be completely effective at preventing the infestation from spreading. These treatments are effective when applied during or prior to the emergence of adults in the spring, early summer, or fall, and it is recommended that trees be treated annually for three consecutive years.
References
Camper, M., and W. Cranshaw. (n.d.). Asian Longhorned Beetle in Colorado – Identification of Insects and Damage of Similar Appearance. Colorado State University – Extension. Available https://webdoc.agsci.colostate.edu/bspm/Hexapoda%20(Insects)/Asian%20Longhorned%20Beetle.pdf
Coyle, D., R. Trotter, M. Bean, and S. Pfister. 2021. First Recorded Asian Longhorned Beetle (Coleoptera: Cerambycidae) Infestation in the Southern United State Journal of Integrated Pest Management. 12(1): 1-6. Available https://academic.oup.com/jipm/article/12/1/10/6166961
Hajek, A. 2007. Encyclopedia of Pest Management – Asian Longhorned Beetle: Biology and Control. CRC Press: Taylor & Francis Group. 2: 21-24.
Hu et al. 2009. Ecology and management of exotic and endemic Asian longhorned beetle Anoplophora glabripennis. Agricultural and Forest Entomology. Available http://www.cerambyx.uochb.cz/assets/pdf/hu_et_al_anoplophora.pdf
LaForest, J. 2013. Anoplophora glabripennis. BugwoodWiki. Available https://wiki.bugwood.org/Asian_longhorned_beetle
Meng, P., Hoover, K., and Keena, M. 2015. Asian Longhorned Beetle (Coleoptera: Cerambycidae), an Introduced Pest of Maple and Other Hardwood Trees in North America and Europe. Journal of Integrated Pest Management. 6(1):1-13. Available https://academic.oup.com/jipm/article/6/1/4/788453
Oten, K. 2021. Asian Longhorned Beetle. North Carolina State University – Extension. Available https://content.ces.ncsu.edu/asian-longhorned-beetle
Pimentel, D. 2007. Encyclopedia of Pest Management: Volume II. Cornell University. 21-24.
USANPN. (n.d.). Asian Longhorned Beetle Forecast. USA National Phenology Network. Available https://www.usanpn.org/data/forecasts/Asian_longhorned_beetle#:~:text=Non%2Dnative%20Asian%20longhorned%20beetles,leaving%20perfectly%20round%20exit%20holes.
USDA. 2023. Asian Longhorned Beetle. United States Department of Agriculture – Animal and Plant Health Inspection Services. Available https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/pests-and-diseases/asian-longhorned-beetle/asian-longhorned-beetle
USDA, 2022. Asian Longhorned Beetle Insecticide Treatments. United States Department of Agriculture – Animal and Plant Health Inspection Services. Available https://www.aphis.usda.gov/publications/plant_health/fs-alb-insecticide-treatments.pdf
USDA. 2016. The Asian Longhorned Beetle: An Invasive Tree Pest. United States Department of Agriculture. Available https://www.aphis.usda.gov/publications/plant_health/2016/book-alb.pdf