Cynipid Wasps

For more detailed information, read and download the free Extension publication, Gall-making Insects and Mites – E-397.

Cynipid wasp emerging from an oak gall

In early spring, when oak tree leaves first appear, species of gall wasps (Hymenoptera: Cynipidae) from last year’s galls emerge, males and females mate and females insert eggs in expanding leaf tissue. If successful, the presence of developing cynipid wasp larvae stimulate development of galls – often specific in shape and color to a particular species. Once galls begin to form, insecticides are ineffective in stopping growth or affecting developing larvae.


  1. Would it be good to just remove the gall before the the wasp emerges and lays her eggs? I’ve only noticed one gall so far on my young red oak tree.

    Comment by Mary Coppinger — June 11, 2014 @ 9:46 PM

  2. A single gall is of absolutely no consequence to a tree. I would leave it as part of nature’s course. When galls are present, natural enemies of galls will come and occcupy at least some of the galls. These checks and balances of nature seem to work OK for trees, and as long as we don’t disrupt the system unduly with pesticides or with stresses to the tree.

    Comment by m-merchant — September 23, 2014 @ 5:15 PM

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