Asian Longhorned Beetle February 2001 by Ed Lee

The Asian longhorned beetle (ALB) has been discovered attacking trees in the United States. This recent introduction probably came to the U.S. from China inside solid wood packing material. The tunneling by the beetle larvae girdles tree stems and branches. Repeated attackes lead to dieback of the tree crown and, eventually, death of the tree.

In the U.S. the beetle prefers maple species (Acer spp.), including boxelder, Norway, red, silver, sugar and sycamore maples. , Other known hosts are horsechestnut, black locust, elms, birches, willows, poplars and green ash.

Be on the alert for this significant pest of trees.

Damage to Trees

Female Asian longhorned beetles chew depressions (oviposition sites) in the bark of trees to lay eggs.  A single female beetle can lay from 35 to 90 eggs.  Hatching within 10 to 15 days, the worm-like immature beetles tunnel under tree bark and bore into healthy hardwood trees.  The beetle larvae feed on living tree tissue during the fall and winter and, after pupating, emerge through exit holes during the spring.  After emerging, adult beetles feed on tree exteriors for 2 to 3 days, then mate.  Adult beetles remain active only during summer and early fall months before perishingócompleting a 1-year life cycle.

Look for trees damaged by Asian longhorned beetles.

After maturing, Asian longhorned beetles leave behind deep, perfectly round exit holes somewhat larger than the diameter of a pencil.  Tree exit holes may ooze sap, and deposits of frass (insect waste and sawdust) may collect at tree trunk and tree limb bases.  Egg deposit sites can be found by looking for dime-sized, dimpled impressions in tree bark.

Unseasonable yellowing or drooping of leaves when the weather has not been especially dry are also signs that the Asian longhorned beetle is present. Leaf symptoms show up when the immature insects, growing inside the tree, have bored through tissue that carry water (xylem) from tree roots and nutrients (phloem) from the leafy canopy above. Once the pest has sufficiently disrupted those pathways, the infected tree will die.