Grape mites are probably the least serious disease in vines. The development of small bumps appearing on the leaf surface, resembling the "smallpox" disease, is very alarming at first glance. On the underside of the leaves there are small hollows with a white furry web. The minuscule mites live in the webs. By sucking on the leaf, they produce growth deformations, which hardly limit the function of the leaf and are harmless to the plant, and the little animals themselves are harmless to humans. No other plant species is infested by them. The only problem is that they may multiply considerably and the aesthetic of the vine may suffer. Infested leaves can be removed to stop the spread of the mites. Further measures are usually not necessary -- after bad infestation, a light sulfur treatment in the next spring might be in order.
(Grape mites - eriophyes vitis)