Oak Bullet Gall Wasp

Problem type: Insect

Name of problem: Oak Bullet Gall Wasp

Plant name(s): Bur oak

Symptoms / Characteristics:
Round to oval, woody structures (known as galls) with a rough surface, measuring about ½" in diameter. Fresh galls are green in color. Dried galls turn brown to black. They are found on twigs and branches in clusters of usually three or more.

The young are white, legless larvae with no distinctive head which are found in the galls. Adults are a cynipid wasp. Females emerge in the fall and lay eggs near bud scales. Eggs hatch in the spring and larval feeding stimulates gall formation. Adult wasps are less than ¼" long, black to brown in color and are ant-like in appearance. There is likely more than one generation per season.

Galls may cause injury to the tree but healthy trees are rarely damaged. Generally they are not harmful. Heavy infestations are unsightly.

Control / Preventions:
Prune off branches with galls