Egg-Brown, round, and depressed, the egg (0.15 mm wide) is faintly striated around a central seta.
Larva-The larva has six legs and is pale brownish pink.
Nymph-Except for its smaller size, the nymph resembles the adult.
Host Plants -Spruce spider mites feed on spruce, hemlock, arborvitae, pine, Douglas fir, Fraser fir, and various conifers in nurseries and foundation plantings.
Damage -The spruce spider mite is regarded as the most destructive spider mite feeding on conifers in the United States. This pest causes needles to yellow or brown and drop off prematurely (Color Plate 4EE). With a serious infestation, the plant may be webbed. After several years of the mites' heavy feeding, the plant may die.
Life History -Spruce spider mites overwinter as eggs usually laid at the base of needles. In April and May the eggs hatch, and larval mites begin to feed. The mites develop through a series of nymphal stages, reaching the adult stage in 4 to 5 weeks. As the season advances, so much overlapping of generations occurs that all stages are present at once. Spruce spider mites seem to be "cool weather mites," maximum feeding and reproduction taking place in spring and fall. Virtually inactive in hot weather,they are subject to attack by predaceous insects and mites, which usually decimate the population during the summer.
Because the spruce spider mite is most active in cool weather, infestations should be treated at the end of summer or winter for maximum effectiveness. Multiple foliar applications of proper miticides at 2-week intervals may be needed to obtain desired control. For specific chemical controls, see the current state extension service recommendations.
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