European red mites overwinter as bright red eggs laid in clusters on branches, limbs and trunk, often in such great number that the bark seems to be covered with red brick dust. Eggs of subsequent generations are laid on the foliage, usually on the lower leaf surface. Following spring egg hatch, there may be several generations per year. Despite its common name, this mite feeds on more than 40 species of conifers. The mites have a similar appearance to those already discussed.
Coloration varies from green to deep olive to brownish red.
Close inspection of the needles will reveal tiny white flecks and speckles where the mites have fed. Prolonged feeding causes yellowing, browning, and premature needle drop, often originating from the canopy interior. Infested foliage may also display webbing, eggs and cast skins. Heavy attacks can cause branch dieback or death of the plant. The spruce spider mite is known as a cool season mite and is most active in early spring and late fall.