Defoilators on Garry oak (Quercus garryana)- aging a garry oak without boring it.

Asked July 12, 2019, 4:24 PM EDT

Can you please help me identify the defoliators on this oak. I have attached a few pics of insects I found on the leaves. One is an aphid like insect. The tips of the leaves are rolled, where a worm is hiding underneath. Please refer to pics. Not sure whether both of the insects are related or attribute to the defoliation. Are these insects considered a problem?

Another question. Is there a way of ageing a Garry oak without boring it. I have heard that every cm of diameter is equal to 2-3 years. Therefore a tree 60 cm DBH tree would be 120-180 years. Fact or fiction or reasonable?

Thank you


Oregon forestry insect issues oaks

2 Responses


I've been working with Christine Buhl , ODF Forest Entomologist, on identifying these insects and there appears to be several different ones working together. There is a leaf roller and a leaf miner involved. We do not have a species identification yet.

I'm seeing this very common in my area in Benton and Linn Counties for sure.

The impacts seem to be related to early spring damage, but it appears the peak is over and the damage done. Looks like it has reduced leaf area. on lots of trees, but the trees will likely do ok. We don't think these will kill trees.

There may be some general information in this publication from California:

I hope this is helpful.

Terrific. Thank you so much for you help.