Beetles Destructive to Northwest Fir Trees

Affected Trees

• Several fir trees are native to the Northwest. Examples include white fir (Abies concolor), hardy in U.S. Department of Agriculture plant hardiness zones 4 through 7, which bears silvery needles, and Pacific silver fir (Abies amabilis), hardy in USDA zones 7a through 9a, which bears striking purple cones. Other natives are the subapline fir (Abies lasiocarpa), hardy in USDA zones 2 through 9, the noble fir (Abies procera), hardy in USDA zones 5 through 10, and the grand fir (Abies grandis), hardy in USDA zones 4 through 9.

Fir Engraver Beetles

• Fir engraver beetles are shiny, black, and about 1/16 inches long. They emerge from infested trees during the warmer months, usually about June through September. Adults fly to other trees and prefer those that are about 4 inches in diameter or greater. The beetles mate in the new tree and the female bores a track between the outer and inner bark. Symptoms include frass (looks like fine sawdust), yellow or red branches, holes in the bark and streams of pitch. They most often attach to white fir, subalpine fir, noble fir and grand fir.

Silver Fir Beetle

• The silver fir beetle is about 1/8 inch long with a stout brown body. It bores into the bark of fir trees and creates tunnels between the bark and the wood. Evidence of attack includes the presence of a reddish frass and small entrance holes in bark crevasses; these are difficult to see because they often occur under mosses, lichen or bark scales. The pests most often attack Pacific silver fir, but also attack subapline fir, grand fir and noble fir.

Other Beetles

• The western balsam bark beetle and the fir root bark beetle attack fewer species but are equally as devastating. The western balsam bark beetle is about 1/8 inch long, has a dark brown to black body and is somewhat hairy. The fir root bark beetle can get to 1/4 inches long and feeds on the lower portion of the tree's bark, sometimes below ground level. Both produce frass when boring into trees, and branches may turn yellow to red. There may be pitch flowing from the boring holes. The western balsam bark beetle tends to attack subapine fir, while fir root bark beetle tends to attack Pacific silver, grand and noble firs.