The mite Acalitus calycophthirus galls the buds of Betula pendula and B. pubescens causing the affected bud to enlarge.  These galled buds may contain a large number of mites.

A good photograph of the gall is required.  Please state the host species.

The galls may be found where the host Birch species occur. Found on Betula pendula and on B. pubescens.

The gall can be found throughout the year but most noticeable in winter. Harder galls are formed on Betula pendula and these can remain for several years.

It seems to be widespread in Britain, but is not well recorded.

Status in Leicestershire and Rutland not known.