They spend the summer as eggs that hatch in the fall for a short feeding time before winter. Scout for spider mites by vigorously shaking or striking the foliage over a white piece of paper. Some of the mites will fall onto the paper where they can be seen as tiny, moving dots. Smashing them will produce greenish or yellow-orange streaks. Numerous predaceous mites will reduce the need for chemical control.
Damage appears as light to brownish dots or stippling on the needles.
The mites feed on cells of the leaf, removing and destroying the chlorophyll. This creates a light spot that dries and turns brown. From a distance, the foliage appears bronzish, dirty, or bleached. Heavily attacked foliage will turn brown, and severe attack can kill branches and trees. These mites attack spruce, juniper, pine, arborvitae, hemlock, and Douglas-fir.