Oregon White Oak Disease

Asked June 14, 2020, 10:04 PM EDT

I live in Fall Creek, Oregon within Lane County. I have many Oregon White Oaks. Most Of them appear to have a disease where the leaves are brown around the edges. When I looked closer at a specific leaf if I could see the pink sacks on the under side as well as what looked like a very tiny holes in the leaves and sections were perhaps an insect had laid eggs on the leaf itself. I’d be grateful for someone to help me identify this disease and let me know if it is likely going to kill the trees and if so, what can be done to remediate and protect against this disease. Thank you for your help.

Lane County Oregon

2 Responses

Hello, this is an issue we've seen around the Willamette Valley last year and this year. It appears to be caused by a complex of several insects which are moth caterpillars. The larvae of the moths are tiny at first and may actually mine the inside of the leaf, also, scape the leaf, eat between the veins, and when larger, will roll the leaf and feed inside. This seems to ebb and flow, and we don't think it is a huge issue for the tree. We might predict that next year should not be as bad. There is really no way to control it, so we hope for the best.
This reference about California oaks is a good one and describes an insect we think may be involved, see page...16 fruit tree leafroller
Field Guide to Insects and Pathogens of California Oaks

Concerning the round pinkish balls. Those are galls, caused by a cynipid gall wasp. Various galls occur on oak leaf, and twigs, and each type of gall is caused by a different gall wasp species. We don't think these galls cause much damage to the tree. This book is great: https://www.amazon.com/California-Western-States-Natural-History/dp/0520248864

But out of print I guess and maybe spendy.

Thank you David. That is super helpful! I have noticed that there is quite a bit of variation from one oak to the next and in different groves of oaks as well. Some look like the extensive damage to leaves would kill the tree, but I hope I am wrong.

Best regards,