Spruce spider mite
July 31, 2015
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EmailOligonychus ununguis
This mite overwinters in the egg stage on buds and needles. It is active during cooler weather in spring and fall. Nymphs are present in spring as saucer magnolia or Norway maple begins to bloom. Look for active spruce mite infestations in the fall as goldenrod is blooming. Hosts for spruce spider mite include fir, pine, yew, arborvitae, juniper and Douglas-fir. The size of the mites is less than 0.5 mm.
Damage
Look for stippled needles, especially on older growth. Mites will be visible with a 10x hand lens. Old eggshells will be clear; viable eggs are red. Young nymphs are red, turning dark green as they mature. Webbing may be present.
Management
Sampling mite populations by shaking an infested branch over white paper will help to estimate populations. Low numbers may be controlled by predatory mites if they are present. If miticides are needed, select specific miticides that spare predators.
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