Oak galls

Symptoms - Bizarre structures develop an oak's foliage, buds and acorns. This will happen mainly in late summer but some develop in the spring. There are more than 30 species of gall wasps in Britain on the common oak. Each species lays its eggs in a particular structure on the tree - the roots, bark, buds, leaves, catkins or acorns. Chemicals secreted by the wasp grub alter the normal cell division process and cause the plant to produce gall tissues that enclose the grubs. These vary in shape and size.