My piñon trees have piñon needle scale. Do yours? The spots are a protective covering over the scale insects. This covering protects them from the weather and many insecticides. The insects feed by drinking the sap from the needles. This insect does not kill the tree quickly; it debilitates the tree. Over time the weakened tree may die. You have probably noticed that the needles with the black spots will turn yellow, then brown, and fall from the tree in the spring. The scale reduces the length of time the needles remain on the tree, thereby reducing the ability of the tree to feed itself.
The recent drought imposes another stress on trees and, in combination with the stress from the scale insects, may be enough to kill the tree in a few years. The recent attack of pine bark beetles associated with the drought is another threat to already debilitated trees.
The simplest thing to do is use a strong blast of water. You will not remove all the eggs, so there will be some scale remaining in the tree, but the level of infestation should be reduced enough to greatly lower the stress on the tree. Plus the additional water allows the tree to protect itself better.
Piñon needle scale close up
Piñon needle scale
