WSU Extension

Hortsense

Common Insects & Mites : California gallfly
(revision date: 4/30/2013)


Biology
The gall of this cynipid wasp larva is the largest and most conspicuous of the galls on oak. It is a twig gall that is often called 'oak apple'. It starts out green and gradually 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 generally round and sometimes kidney-shaped. During its development, the gall may host up to a dozen larvae.
Management Options

Non-Chemical Management
  • Hand remove where practical.
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