Marble galls on oak

Caused by a tiny gall wasp laying eggs in oak buds, these galls develop through the summer and turn brown in August when the new wasps emerge.

They are all female and fly to Turkey oaks, if they can, and lay their eggs in the buds, forming little galls like an ants' eggs.  These develop over winter and in late spring out come female AND male wasps.

After mating the males die and the females fly to native oaks and start the cycle over again by laying eggs in the buds.

Marble galls are more common on very young or stunted oaks.

This species of gall wasp, Andricus collari, arrived in Britain in the 1830s from the middle east.  Oak trees seem to cope with them quite well.