Galls Of Oak

Disease Information


 Symptoms and damage

There are at least 750 different galls that have been identified on oak. In fact, more galls occur on oak than on any other kind of plant. Galls are defined as irregular growths or swellings. They vary greatly in size, shape and their location on the plant. Gall development is a reaction by the plant tissue to feeding or egg laying by various mites and insects. While most galls do not seriously harm oak trees, most are unsightly and detract from the beauty of the tree. Twig galls may kill individual limbs and sometimes the whole tree.

Many gall-producing insects and mites are parasitized by other insects and are fed upon by various birds and animals. Simple removal and destruction of fallen leaves with galls will help to reduce the number of emerging adults that will produce the next generation. Where possible, all twig galls should be pruned out while green or before emergence holes appear. In most cases, chemical control is not practical or effective. This is especially true in the case of large trees.


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