Eriophyes cerasicrumena

Several generations each year. The first galls develop April to July.

black cherry (Prunus serotina var. serotina)

Tiny, almost microscopic

Eriophyid mites (Eriophyes spp.) are so small that they are almost impossible to see with the naked eye. Unless a scanning electron microscope is available, a morphological description of an adult individual is useless. The mite is most easily identified by the shape of the gall it produces and the plant species on which it is found.

Black cherry finger gall mite is a highly specialized plant feeder. As its common name suggests, it is found exclusively on black cherry (Prunus serotina var. serotina).

The pouch-type finger galls appear on the upper side of a black cherry leaf. They are solitary, though there are usually many galls on a single leaf. They are often crowded near the base of the leaf blade and near the midrib.

Each gall is yellowish-green, brownish, or reddish; spindle-shaped; hollow; and ⅛″ to 5 ⁄16″ long. It is attached to the leaf blade by a slender stalk and is pointed or tapered at the tip.

Adult mites appear in three morphologically distinct forms. The female that feeds in the growing season (protogyne), the male, which also feeds in the growing season, and the female that overwinters (deutogyne).

This is the only species that causes finger galls on black cherry. It is not found on other plant species.

Leaves of black cherry (Prunus serotina var. serotina)

The overwintering female (deutogynes) emerges with the leaf from the leaf bud in the March, “riding” the leaf out as it grows. As it feeds on the leaf, a chemical in its saliva causes the leaf cell to expand, forming a pouch. It then enters the pouch, lays its eggs, and dies. In May the eggs hatch, producing males and white, growing-season females (protogynes). These mites remain in the pouch through the summer. In July, red deutogynes appear. In September the gall dries and splits open, releasing all three forms of the mite. The deutogynes enter the buds to overwinter.