How to Manage Pests

Gall and blister mites

(Eriophyid mites)

Eriophyid mites cause blistered leaves or galled twigs on many landscape plants including alder, aspen, baccharis, beech, elm, grape, linden, maple, and walnut. The mites occur in yellow to orange felty masses in depressions on the underside of blistered leaves.

Damage

Mites may cause warty, woody swellings on twigs and green or brown raised blisters on leaves. Blistered leaves may become curled or grossly distorted. On conifers, some eriophyid mites feed in needle sheaths and can cause stunting, yellowing, and distortion of new needles.

Solutions

No controls are known or recommended for most eriophyid (gall and blister) mites. Eriophyids cause aesthetic damage and may reduce fruit yield, but do not seriously harm woody landscape plants and can be tolerated. Prune and dispose of infested leaves. When mites are abundant, the most important actions are to conserve natural enemies and to provide proper cultural care to keep plants vigorous with proper irrigation and fertilizer.