WSU Extension

Hortsense

Oak : California gallfly
(revision date: 4/28/2014)


Biology
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

Non-Chemical Management
  • Hand removal where possible.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images
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Caption: California gallfly "oak apples"
Photo by: R.S. Byther