Acalitus plicans is an eriophyid mite which causes galls on beech (Fagus sylvatica).

The leaf is distorted and crumpled with folds, and is covered with reddish hairs.

The reddish tinge resembles an emerging leaf, which together with the small size makes the gall easy to overlook.

The mites live and feed among the hairs which are deep in the folds of the leaf and overwinter under the bud scales.

Countries where it has been recorded include Belgium, Czech Republic, Germany, Great Britain, Latvia, Lithuania, Poland, Russia, (Kaliningrad) and Slovenia.