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Signs and symptoms of a tree-killing pest

August 25, 2009

Never a dull moment exists in the field of invasion ecology - new species, like the Asian longhorned beetle (ALB), keep arriving on the scene. ALB has the potential to eliminate sugar maples from New York's forests, thereby ending syrup production, impacting timber production, reducing the scenic splendor of our fall foliage, and dramatically changing the composition of our forests forever.

Since this is a slow moving beetle still found in only spot infestations rather than across broad areas of multiple sites, eradication of the ALB is thought to remain possible and a focused program attempting to eradicate it from North America has been initiated. The U.S. Department of Agriculture's Animal and Plant Heath Inspection Service also launched a public education campaign in conjunction with states from Pennsylvania to Maine alerting individuals to actions they can undertake to protect our forests and forest products. Part of this campaign was designating the month of August as Asian longhorned beetle awareness month.

The ALB is an exotic wood-boring insect native to eastern Asia that arrived in the U.S. via infected wood pallets. First detected in Brooklyn in 1996, it is now present in New York City, New Jersey, and, most recently, Massachusetts. Adult beetles are usually present from July to October. The beetles are big - they range in size from 3/4 to 1 1/4 inches long - and are jet black and glossy (sometimes compared to 'patent leather shoes') with white spots on their backs. They have long, black and white banded antennae that are 1 1/2 to 2 1/2 times the length of their bodies.

Article Photos

Asian longhorned beetle
(Photo provided)

ALB attacks a long list of hardwood forest and landscape trees, but some favorites include sugar maple, red maple, silver maple, American elm, willows, poplars, and birches. Each female can lay up to 160 eggs that hatch in 10 to 15 days. The larvae then tunnel under the bark and into the wood where they eventually pupate into the adult. Adults emerge by boring a tunnel in the wood. Tunneling by larvae and adults girdles tree stems and branches. Repeated attacks lead to dieback of the tree crown and, eventually, death of the tree. Landowners are often the first to detect infestations.

You can help by looking for these signs of ALB damage on host trees:

1. egg sites about 1/2 inch in diameter where the female beetle chewed out a groove in the bark to lay her egg. The sites may look orange when fresh but will turn grey when older.

2. Accumulation of coarse "sawdust" (frass) around the base of an infected tree or where branches meet the main stem.

3. Oozing sap from wounds made by the beetle (in maples only).

4. Round exit holes (between 3/8 to 3/4 inches in diameter) where adult beetles have emerged.

5. Severely damaged trees generally have upper branch breakage exposing galleries at the break and crown dieback.

6. Leaf feeding damage that has jagged cutouts where the leaf midvein has been eaten away by the adult beetle.

Major ALB pathways include wood packing material, wood and firewood. Areas of high risk of introduction include campgrounds, including primitive sites with road access; second homeowners whose primary residence is in ALB-infested/quarantine areas; sites that receive large-diameter solid wood packing materials from Asia; wood near landfills, dumps, and transfer stations that accept wood debris; residential properties where firewood may have been brought in from quarantine zones; and firewood processors and sellers.

ALB can be easily confused with the native whitespotted sawyer, which is drawn to dying, stressed, or recently felled conifers. Both have white spots, but the whitespotted sawyer also has a white spot between the wing covers (where the insect's "shoulder blades" would meet). If you suspect an infestation or think you found ALB, collect an adult beetle, place it in a jar in the freezer, and contact the Adirondack Park Invasive Plant Program at 518-576-2082 x 131, or your local Cornell Cooperative Extension office.

Currently, the only effective means to eliminate ALB is to remove infested trees and destroy them by chipping or burning. Using local firewood and detecting ALB infestations early are essential to combat its spread.

'Eye on Invasives' is a biweekly column that spotlights a top invader when it is easiest to identify. The Adirondack Park Invasive Plant Program is a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley. Find out more about this award-winning program online at



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