Pests and Diseases: Galls on Trees

I have a white oak (Quercus alba) that lives in my backyard. It’s home to birds and squirrels and galls. Galls on trees are a pretty common occurrence but they can cause great concern to gardeners. Is there really cause for concern? Let’s take a look.

Galls are a growth that occurs on the leaves or branches of trees as a result of a myriad of pests. These pests can include fungi, bacteria and nematodes although the most common are insects and mites. When the insects and/or mites invade the tree, a gall is formed by the tree and the pest is protected inside. The gall also serves as a food source for the pest. For the pest, it’s pretty much a win-win; it’s protected and fed by the gall.

Galls on trees may be unsightly but there really isn’t much need for concern by the gardener. Once the gall has formed it’s going to stick around for a while. No amount of spraying will remove the galls and they don’t take a tremendous amount of energy away from the tree. Consider them an anomaly and let them be. If you are truly concerned about them, consult a Certified Arborist or your local extension agent.

For curiosity’s sake, let’s take a look at some pictures of galls.

galls on trees
Photo courtesy of


galls on trees
Photo courtesy of
galls on trees
Photo courtesy of


Do you have any experience with galls on trees? If you’d like to share with the Mid-Atlantic Gardening community leave me a comment below or send me an e-mail. If you enjoy being part of the Mid-Atlantic Gardening community, join our e-mail list (upper right hand corner of this page), become a fan on Facebook and follow me at Twitter. Happy gardening!

May 29, 2012Permalink 3 Comments

3 thoughts on “Pests and Diseases: Galls on Trees

  1. We have galls on many of our oak trees from wasps. You can split them in the winter to find grubs. They’re too small to use for ice fishing bait but still fun to look at.

    It’s also fun to check the goldenrod for grubs in the winter. Sometimes you can find one the birds haven’t. Now, those grubs make good bait.

  2. OK so I’m curious. You say to check the goldenrod for grubs…where are the grubs? At the roots?

    And yes, the galls on the oaks are from wasps here too. Nature is a wild thing!

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