Maple Bladdergall Mite

You will see small brilliant red bladder-like galls rising from maple leaf surfaces, especially on silver maple and red maple, starting in May or June. Galls enlarge to about one-eighth inch, eventually turning black or brown. Severe infestations may cause leaf distortion and premature drop. The microscopic mites trigger these galls while feeding beneath leaf epidermis throughout spring and early summer.

Bladdergalls are primarily cosmetic and require no control for tree health. Heavy infestations trigger leaf drop, effectively shedding infested leaves. Galls cease forming by July as mites move to bark crevices for dormancy. No control is warranted for individual galls. Prune affected branches only in severe cases.