Maple Bladder Gall

Description:

The upper surface of silver and red maple leaves often become covered with small, red, round wart-like structures about 1/16 to 1/8-inch in diameter. These are maple bladder galls caused by a small mite, Vasates quadripedes (Shimer). The structures are generally noticed first in May, about the time the leaves have become fully expanded. At first the galls are green but they quickly turn pink to red and eventually black. Leaves frequently become so covered with the galls that they completely twist out of shape and may even drop early.