Maple Bladder Gall Mites

Susceptible Plants

Silver Maple, Acer saccharinum L.


  • Mites are tiny creatures, about 0.2 mm long, with two pairs of legs.
  • Dispersal is mainly through wind currents.
  • Fertilized females overwinter in bark crevices of their host.
  • In spring, they move onto the new foliage and inject their saliva into the leaf tissues.
  • This stimulates the formation of a gall (growth) on the upper side of the leaf. The galls are small raised bumps on the leaves. They are often bright red.
  • The mites move into the galls and lay their eggs inside to start the next generation.


There is little damage to the tree. Sever infestations look unsightly, and may cause the leaf to appear deformed.


Control is not usually necessary for tree health. Treatment is done for appearance. It must be done in early spring when the new leaves are emerging. Root-drench with benomyl (Benlate) to control the mite population.

Compiled by: Dr. Bill Paton and Shauna Peters