Are Gall Wasps Bad For Trees?

Among the many pests that attack trees, gall wasps are relatively small. They lay eggs in leaf tissue and install a chemical that makes the gall grow. They do not sting or eat humans, but they are preyed upon by smaller insects and birds. They live for a short time and then die.

There are many species of gall wasps. They include Cynipid wasps (Andricus quercusfoliatus) and Megastigmus brevivivus.

The life cycle of gall wasps is a complex one. First, the tiny wasp larva grows into a pupa and then into an adult wasp. The larvae overwinter in the cracks of soil. The adults emerge in spring. The tiny wasps feed in the stem for nine to ten months before they re-infect the tree.

The gall itself is a tumor shaped by chemicals in the wasp’s saliva. These chemicals trick tree cells into creating a tumor around the egg. This is not unusual.

In addition to galls, other pests may be present, including fungi and woodpeckers. Galls may be found on shrubs, fruit crops, and perennial flower foliage. Some galls contain extrafloral nectaries, which are nothing to do with gall development.

The best way to deal with gall wasps is by applying a combination of safe and effective control methods. Using IPM (integrated pest management) is one approach to keeping gall wasps under control.

Galls are not harmful to the tree, but they are not good for the environment. Many species of gall wasps require oak trees as their hosts.