Oak twig gall?

ATH · Aug 9, 2015

I mentioned earlier this is the summer of questions for me! There are usually a few pests problems here and there within a year that I have to dig more to figure them out, but I think I hit my yearly quota in less than a month! Here is an unresolved one from about a month ago...they were too dried out by the time I got the USB microscope. In fact, this was the last push----once I sent out a couple of e-mails and asked a couple of others what they thought and came up empty, I figured that would be a good investment.

I am pretty sure this is some kind of gall-forming insect....but the tissue is not nearly swollen enough for a "normal" gall. The twigs are slightly deformed, and notice the exit holes. This is on several bur oak trees - some 40"+ dbh and in decline. It is also on a smaller bur oak. The bigger ones are not doing well. They also have Kermes scale. There were also some grade changes that certainly impacted the tree health.

And finally, the scale on this tree:

lindnova · Aug 10, 2015

I don't have an answer but have the same question. I have a small bur oak in the backyard (8' tall) that has those small galls. Hopefully that isn't contagious to other trees.

I have noticed this year is rough on the oaks. I have two pin oaks that died suddenly probably oak wilt. The bur oaks have a lot of bugs eating leaves this year and thinning out the canopy, with a few looking like oak wilt is on them also.

Raintree · Aug 10, 2015

It looks very similar to the oak crypt gall we are dealing with on Cape Cod. Over 700 types of galls occur on oaks alone, without the adult insect ID is difficult.

Cynipid gall wasp
Andricus quercusradicis

ATH · Aug 10, 2015

That is certainly the closest I have seen so far. I am honestly not 100% certain that it is truly a "gall" forming insect that is leaving the holes, but sure seems suspicious. Complicating the equation is the Kermes scale that causes distortions of its own...so is it the bug that is making these holes or the Kermes? If it is not the bug making the hole causing distortion, then is it a gall maker???

It is 30 miles from me, so not realistic to trap for adults...especially when I don't know when I should be trapping because I don't know the life cycle of the thing I don't know what it is!

What is this wasp attacking up there and what does it do to the tree...and is there any stopping it? (I know most galls are not easy to effectively deal with).

Raintree · Aug 11, 2015

Split open a twig it may look like this gall wasp infested pic...

Some info on the crypt gall wasp, http://www.capecodextension.org/wp-...ees & shrubs/Cynipid Gall Wasp Fact Sheet.pdf
It's also a vector for Bot canker, combined with the winter moth our oaks are not happy on the coast.
Guys with bigger heads than mine are thinking the population will crash soon.

ATH · Aug 11, 2015

Hopefully the population does crash! Anything you are doing to try to control it/protect trees? Or just the standard "maintain tree health"?

Del_ · Aug 11, 2015

I don't believe these galls cause serious damage, only cosmetic. The wasp population will vary with winter temperature and may go into decline all on their own if left untreated. Very hard to treat anyway. I've seen severe cases but the trees lived on. Maybe even a natural type of crown reduction.