The galls are usually a brilliant red and may resemble a bladder,
spindle, or a dense mass of hairy or bead-like growths called erinea
(0.15 mm in diameter). The galls may form on either the upper or
lower surfaces of the leaf. Some of the erineyum-type galls may
resemble felt patches or when magnified have a texture similar to
a beaded surface.
on image for larger version
Figure 1. Eriophyhes spp. Mite Gall on Silver