Wool Sower Gall

Cocoon on Oak Tree Branch?
Hi — I found your website through Google. I live in central Missouri and found this "weird growth" on a branch of one of the oak trees in my yard. I’ve tried researching the web, but I still can’t identify if it’s a plant fungus, or a gall, or a bird nest, or a cocoon, or something else! Do you have any idea? It’s about the size of a ping-pong ball, white with pink spots, and it’s "perched" on top of the branch. Very strange. Thanks!
Susan Foster

Hi Susan,
In the true sense of the word, this is not a cocoon though adult insects will emerge. You have a Wool Sower Gall which is produced by a tiny wasp, Callirhytis seminator. Galls are growths on various parts of plants, usually caused by a Gall Wasp or a type of mite. There are many species of Gall Wasps, and each has a specific host plant. The Wool Sower Gall used the oak tree as a host. Here is a site with additional information.

Leave a Comment