Rhizopus stolonifer rots berries very quickly. These turn brown on red grape and / or take on a beigeish tint on white grape (figure 1).

The skin of the berries is quickly more or less decomposed (figure 2); it splits and juice flows are noted.

An abundant black mold, rather aerial, made up of numerous fruiting bodies in "black pinheads" (figure 3) forms on the damaged tissues.