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About the Asian Longhorned Beetle
The Asian longhorned beetle (Anoplophora glabripennis) is a highly invasive wood-boring insect native to China and the Korean Peninsula. First detected in the United States in 1996, it is believed to have arrived in solid wood packing material used in international shipping.
The Asian longhorned beetle attacks a wide variety of hardwood trees. It is especially destructive to maples, but also infests birch, elm, willow and horse chestnut trees. Asian longhorned beetle larvae bore deep into the heartwood of trees, disrupting the movement of water and nutrients and severely weakening the tree’s structure. Infested trees almost always die and must be removed to prevent further spread.
Back to topLife Stages & Identification
The Asian longhorned beetle is about 1.5 inches long and shiny black, with white spots and blue-white bands on its six legs. It has black and white antennae that can be up to twice as long as their body. Adults are visible between late spring and the first hard frost in the fall.
Female beetles often chew oval or round depressions about the size of a dime or smaller in the bark where they deposit one to two eggs at a time, laying up to 60 eggs. After they hatch, the larvae bore into the tree and start to feed on the living tissue just underneath the bark, disrupting the nutrient and water flow within the tree. The larvae tunnel deep into the heartwood and continue to feed until they are ready to pupate. Repeated attacks from scores of larvae, generation after generation, eventually girdles the tree and kills it. Tree death usually occurs 7-9 years after the initial infestation, depending on site conditions and the tree’s overall health.
Back to topCommon Look-Alikes in Iowa
Several native insects resemble Asian longhorned beetles, but do not pose the same risk:
- Whitespotted sawyer: Native, found on dead or dying conifers; has a distinct white spot between the wing covers.
- Eyed click beetle: Large beetle with two prominent false eyespots on the thorax.
- Cottonwood borer: Bold black-and-white pattern, solid black antennae; associated with cottonwood and willow trees.
- Broadnecked root borer: Dark, heavy-bodied beetle lacking white spots and long antennae.
Correct identification helps prevent unnecessary concern and ensures true Asian longhorned beetle sightings are reported quickly.
Back to topImpacts
Asian longhorned beetle causes extensive internal damage over multiple years:
- Larval tunneling interferes with the tree’s ability to take up water and nutrients.
- Galleries weaken branches and trunks, increasing the risk of breaking off during storms.
- Adult beetles frequently reinfest the same tree, compounding damage over time.
- Infested trees eventually decline and die, regardless of initial health.
Current Location
Asian longhorned beetle infestations have been detected in several U.S. states, primarily in the Northeast and Midwest. These detections have resulted in strict quarantines and large-scale eradication efforts.
- Pathway of introduction: Solid wood packing material used in international trade
- Spread risk: Movement of infested wood, firewood, and wood products
The Asian longhorned beetle has not been detected in Iowa, but continued vigilance is essential.
Signs and Symptoms of Infestation
Asian longhorned beetle damage can be visible year-round. Early detection is critical because eradication programs are most effective when infestations are found early.
What to look for:
- Leaves may turn yellow or typical fall colors in mid-summer.
- Branches or limbs falling from an otherwise healthy-looking tree
- Sawdust-like splintered wood shavings (frass) on the trunk, branches or on the ground around the tree.
- Round holes about the size of a dime in tree trunks and branches when the adult insect chews its way out.
- Oval or round depressions about the size of a quarter chewed into the bark where eggs are laid.
- Sap oozing from egg pits or galleries, especially on maples.
Preferred Host Trees
- Primary hosts: Maples
- Other preferred hosts: Birch, Ohio buckeye, elm, horse chestnut, willow
- Occasional hosts: Ash, European mountain ash, London planetree, mimosa, poplar