Are The Hardwood Trees In Your Yard Dying? This Invasive Insect May Be The Culprit

Are you seeing tiny holes, oozing sap, and thinning crowns on your beautiful weeping willow trees and mighty maples? Don't be too quick to pin it on old age. They could be signs of a much bigger problem—one that might bore its way into every hardwood in your yard. Meet the Asian longhorned beetle (Anoplophora glabripennis). It is an invasive wood-boring beetle that attacks and ultimately kills hardwood trees. And, the problems just don't end with dying trees!

Asian long-horned beetles (ALB) infest, live, and tunnel through the living wood, under the bark. This can compromise the hardwood's structural integrity over time, weakening branches and trees and posing serious safety hazards. Branches can unexpectedly collapse and, during storms, entire trees might fall. Maples are usually at the top of the beetle's hit list, however, it can also attack and infest a broad range of hosts, including birch, elm, willow, poplar, and several other ornamental species. Symptoms of attack appear gradually, but once the beetle establishes itself in a hardwood, problems escalate very quickly.

The signs of damage usually start from the top. You might notice chewed veins or leaves yellowing prematurely in the case of an ALB damage infestation. That's because the larval stages of these invasive insects feed on the inner bark, or phloem of the tree, before moving into sapwood and heartwood layers of the tree. Another tell-tale sign of this invasive insect is its round exit holes about the size of a dime on the tree. The holes might also have sap coming out of them, and you might also see sawdust-like frass accumulating at the base of the tree. 

Unfortunately, once infestation begins, trees usually don't recover. The only thing you can do at this stage is save your other hardwoods. Therefore, if your area is prone to ALB infestations, it is a good idea to do regular inspections during late summer. At this time, adults of this highly invasive insect can be seen feeding on twigs and leaves. Be careful not to confuse them with native lookalikes, such as the white-spotted sawyer beetle. ALBs are glossy black, covered with irregular white spots on the wing covers, and have long antennae.

Since hardwoods don't survive an ALB infestation, the best management practice is removal of the infested tree and proper disposal. The experts recommend chipping the infested wood and burning it to ensure that the eggs and larvae cannot survive. It is also a good idea to report the infestation to the USDA Animal and Plant Health Inspection Service (APHIS) and your local extension services to make them aware. In the meantime, there are some systemic pest-control insecticide treatments that might help save high-value hardwoods. However, they should only be applied preventively by licensed applicators. Insecticides rarely save a tree experiencing an ongoing infestation.