55+ year old fir tree
the tree looks healthy ,but my wife pulled pieces of bark that looked loose and saw dust fell out ,we looked further and found a lot more. The fir next to it exhibits very slight dust. Does the tree have a disease?
Thank you for your question. Without actually seeing the dust and damage you describe it is somewhat of an educated guess but I will give it a try.
There are a number of small insects that can cause the boring dust you can find in and around the exterior bark. They are harmless. There are also bark beetles and wood borers that can attack and kill trees. Bark beetles bore through the bark and lay eggs in the cambium layer (between the bark and sapwood). Wood borers lay eggs on the bark and larvae bore through the bark. Bark beetles can kick out sawdust like material they create in the boring process, which ends up at the base of the tree, on the bark and in cob webs. These beetles can kill standing live trees. Unfortunately, ii the beetles get into the tree there is nothing you can do to save the tree. Bark beetles attack the tree in spring (for the Douglas-fir beetle) but the tree stays green until the following spring, typically. You might also have pitch streams in the mid bole of the tree if it is attacked by Douglas-fir beetle (if your tree is in fact Douglas-fir). I don't know if you have bark beetles or wood borers but if you do you will see the tree needles turn brown and die next spring if it was attacked this year. You could use an axe and chop into the bark to see the cambium area, if it is dark brown/black then the tree was attacked and the beetles are in the tree, if the color is a light sort of creamy color then there are no beetles. My hunch is that the tree is fine and you are seeing some of the harmless small insects that chew on the exterior of the tree. Hope this makes sense.
You could also contact your local OSU Extension Office in Washington County, 1815 NW 169th PL, Beaverton, OR 97006, 503-821-1150 and talk to Amy Grotta, the OSU Extension agent there.