WSU Extension


Armillaria root rot 
Leaf scorch 
Sudden oak death 
California gallfly 
Jumping oak gall 
Leaf galls 
Oak leaf phylloxera 
Oak ribbed casemaker 
Oak treehoppers 
Pit scale 
Stem galls 
Western oak looper 

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Caption: California gallfly "oak apples"
Photo by: R.S. Byther
Oak : California gallfly
(revision date: 4/28/2014)

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


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