What is growing on my young bur oak?

Asked August 12, 2017, 8:53 AM EDT

Earlier this summer I picked off many small black galls or growths on the branches of my oak in southern Mn. They were about 1/2" in diameter. They were firmly attached. Now these cotton like growths have appeared. I suspect they are related. Can you tell me what this is and what I can do about it. See picture. Thanks

Faribault County Minnesota

1 Response

It is a Hedgehog gall (Acraspis erinacei). They are soft, round tufted, ¼ to ½ inch growth with orangish-reddish hairs on leaf surface or underside attached to middle leaf veins. http://www.extension.umn.edu/garden/insects/find/insect-and-mite-galls/