Gall and blister 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.
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.
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.
Growths caused by the walnut blister mite
Live oak erineum mite feeding damage
Stunting and yellowing of new pine needles