Can anyone identify this uniquely distinct pest (a gall I assume?) that I just discovered on my 2 year old Quercus garryana seedlings? These little galls are yellow and red, quite hairy and roughly measure 1/8" in diameter. Should I be concerned? What can/should I do about it? ANY help you can offer would be greatly appreciated! Thanks! Mike
This gall, I think, is caused by a cynipid gall wasp. Which one, is not easy to say - over 600 species in North America. Gall Wasps from Univ. of Nebraska-Lincoln See image 9.1 on this Insect Photo Album from the Lakeshore Nature Preserve, Univ. of Wisconsin It doesn't seem to be a particularly harmful creature for the oak tree.
Thanks for the info - an entomologist at the Pacific Forestry Centre, Victoria, also came to the same conclusion after a friend sent him my photo and the PFC has requested two trees with galls for observation. Those are great links with nice clear pictures. I'm relieved to know it's not serious!! Cheers, M.