The problem is evident in this photo: many Douglas firs on the sunny slopes toward the eastern boundary of ACCF have recently been dying. The total loss is estimated at some 30,000 board feet of timber. What is the cause?
To find an answer to this question, we asked Dave Overhulser, ODF State Entomologist, to visit the site; Dave's wearing the cool orange overalls. Also present at left is Gary Groth, ODF Woodland Assistance Forester, and in center is David Parker, a local forester who harvested trees on this site in past to attempt to stem the loss.
They start by inspecting a small Doug fir with dying needles to diagnose the problem.
In this case there appears to be a canker such as Formalpsis on the tree.
A detailed look at the canker, with affected needles dying at top.
The main thing Dave did during his visit is revealed here. First, he would locate a dead or dying tree. Next, he would chop off the bark on a portion of the trunk to reveal any beetle "galleries" that were present.
Here we see the underside of the gallery, with beetle casings plainly showing up.
Though we've seen evidence of flathead fir borer as the predominant beetle on other trees, this looks more like Douglas fir beetle due to the different shape of the gallery.
This dying tree looks exactly like the others on the outside, but on the inside we don't find any evidence of beetles!
The brown dust you see comes from beetles colonizing a dead tree.
We also had a problem of several blowdown trees in this area; could their roots have been weakened by disease?
We do find that the roots in a second tree carried down as the first blew down are better developed. Possibly some sort of root disease in the first contributed to its blowdown, and the second tree was unfortunately in its way as the first came down.
Other dead or dying trees on other parts of the forest may have been affected by frost damage and not beetle kill. But overall, Dave's verdict was that the beetles simply moved in to finish a job started by the long drought: the culprit, therefore, is climate, not bugs. The solution (short of hand-watering each tree!) is to plant a more drought-tolerant variety (e.g., Ponderosa pine) on drier sunny slopes.