Backyard tree dropping excessive pitch

Asked January 16, 2021, 1:24 PM EST

I have a fir tree in my backyard that drops a large amount of pitch that makes it difficult to enjoy our backyard space. A year ago I had a tree service remove some broken limbs that seemed to be the problem but the tree still drips a lot of pitch. Is there something else I should consider as a remedy or is this natural for the tree?

Lane County Oregon

1 Response

One of my colleagues, Glenn A., gave a very thorough response to this question, so I will mostly copy it here.
If this is a Douglas fir, sap flow from Douglas-firs is rather common and there are various reasons it happens, many we know about and some that remain a mystery.

Sap or pitch flow is often associated with pruning wounds - both old and new. It appears that your trees have been pruned in the past as well as most recently. Some of the pitch on your trees seems associated with old pruning wounds. Pitch moths colonize pruning wounds when pruning is done in spring or summer and the result is chronic pitch flow associated with pitch moth infestation at branch wounds, year after year long after pruning was done. To avoid this, prune in fall and winter, not in spring and summer.

Also, green cones often exude pitch, which becomes particularly noticeable in years with abundant cone crops.

Sap flow from the trunk can also be caused by wood rot fungi - root rot fungi when it is near the base, and stem rot fungi further up the trunk. This can be a more serious problem over the long term as it affects overall tree health and also the risk of tree failure (breakage) due to rotten wood. I do not see obvious signs of this in the photos, but if you see significant sap flow from the trunk that is not associated with branches, a hazard tree evaluation by an arborist may be called for.

Bark beetle attacks also cause sap flow, usually many small streams from many individual beetle attacks. Healthy trees can "pitch out" a small number of bark beetles and not be seriously affected. Trees stressed by drought or other issues can attract beetle attacks and be overcome by large numbers of beetles. Healthy trees are not normally damaged by bark beetles, but they can be overcome by concentrated attack of many many beetles if lots of down wood is left on the ground to breed excessive numbers of bark beetles nearby.