Oak: California gallfly

categories: Oak Oak Insects Ornamental trees Ornamentals

revision date: 2022-11-25 04:31

"Oak apples" caused by California gallfly.
"Oak apples" caused by California gallfly
Photo by: R.S. Byther


The gall of this cynipid wasp larvae is the largest and most conspicuous of the galls on oak, achieving a diameter of one to four inches. It is a twig gall that is often called an oak apple. It starts out green and in time becomes red on the sunny side. Later in the season, the gall turns brown or grayish just before the adult wasps chew their way out. The gall does no apparent damage to the tree and is easily removed without harming the twig. The gall is round, but is sometimes kidney shaped. During its development, the gall may host up to a dozen larvae.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • Hand removal where possible.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • None recommended