Northwest Bigleaf Maple Bark Insects

Carpenterworm

• The carpenterworm (Prionoxystus robiniae) bores into the bark of bigleaf maple trees, creating tunnels in which to feed and live. The larvae of the carpenterworm moth are white and 1/4 inch in length in their earliest stage. They start with dark brown heads, which take on a pink tinge as they mature, growing to a full size of as much as 3 inches. As they begin to transform into adulthood, their bodies turn brown.

Damage

• Carpenterworm larvae chew into the bark of bigleaf maples, creating holes as large as 2 inches in diameter, with frass -- a combination of sawdust and insect excrement -- dropping along the bark or to the ground. Their feeding galleries serve to structurally weaken the trees as sap flows from the wood and the bark becomes gnarled and susceptible to breakage. A severe infestation of carpenterworms can be fatal to a bigleaf maple.

Roundheaded Borers

• Roundheaded borers make homes in dead or dying wood of the bigleaf maple. The adults are beetles also known as longhorned borers. These insects manufacture holes in the bark of a bigleaf maple in addition to staining it and causing sap to ooze from the specimen. This injury results in the bigleaf maple prematurely defoliating, the death of branches and possibly the death of the entire tree. Promptly remove dead limbs and trees to hinder the population of this borer.

Considerations

• Powderpost beetles (Ptilinus basalis) infest dead bigleaf maples and can cause problems in stored lumber that is not properly protected from the insect. Wood-rotting fungi and root pathogens of the Armillaria species are diseases that afflict the tree. Bigleaf maple is native to the Pacific Northwest of the United States; it regularly grows to heights of 50 to 100 feet. A long-lived species, bigleaf maple can reach 300 years of age but attains its mature height potential within 70 years.