Oak Spider Mites Cause Damage to Street, Landscape, and Nursery Trees

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This week I have noticed damage on many pin oaks (Quercus falcata) by oak spider mites (Oligonychus bicolor). Oak spider mites look much like related mites such as southern red mite (O. ilicis), spruce spider mite ( O. ununguis), and maple spider mite (O. aceris). They are dark red to brown with oval to round bodies and orange legs.

Oak spider mite (Oligonychus bicolor) and stippling damage on a pin oak leaf. Photo: SD Frank

Oak spider mite (Oligonychus bicolor) and stippling damage on a pin oak leaf. Photo: SD Frank

Oak spider mites can feed on the upper surface of leaves on oaks and related trees such as chestnut, hickory, maple, beech, and elm.

Oak spider mite feeding causes stippling damage common among mites. Heavily damaged leaves are dull and yellow, becoming tan as damaged tissue ages and dries. Pin oaks seem especially susceptible to oak spider mites as that is where I have seen the most damage lately. Willow oaks also can be heavily damaged and we found that damage increases with the temperature and amount of impervious surface cover around the tree.

Stippling damage from oak spider mites on leaves of a street tree. Photo: SD Frank

Stippling damage from oak spider mites on leaves of a street tree. Photo: SD Frank

Oak spider mites overwinter as eggs on bark. Overwintering eggs may be susceptible to horticultural oil applications. Water trees to reduce stress and don’t over do it on the fertilizer.