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Sometimes, strange
structures appear on the acorns and leaves of an oak tree.
The Oak Apple Gall above is caused by the wasp, Biorhiza
pallida. These oak apples were about 5 cm diameter and
appeared as the leaves were appearing in May.
There are various types of gall and the picture on the
left shows a Knopper Gall, where the acorn has become
yellow, distorted and sticky. These are caused by the gall
wasp, Andricus
quercuscalicis which lays its eggs inside the acorn and
causes it to mutate.
These wasps do not usually cause damage to the tree and
are nothing to worry about. |
