Please help Identify this disease on my Oak

Hello, I am posting this here from another thread I started as recommended by another member to get some additional feedback. Here is my original post.

"We moved into our house last August. Ever since we have lived here, our very large Oak in the backyard has had these tumor looking growths all over it. There are none on the trunk, just on the branches. I didn't know if anyone could help me identify what this might be. They break apart very easily. "

It has been suggested that this is some sort of gall, however, I was hoping to perhaps get a closer hit. Here are a couple of photos I took tonight. If more photos are needed, just let me know and I can take them tommorow.

Thank you!

Amanda

Crap, sorry I can't change this photo now...see post below.

This message was edited Mar 26, 2006 9:28 PM

They're horned/horny oak stem/branch galls. I'd hazard a guess that it's probably a pin oak, though I occasionally see them on other members of the red oak group.
Pin oak has been 'overplanted', almost to monoculture status in residential and street plantings around here, and I'm seeing nice 40-50 yr old trees succumbing to heavy infestations of these galls, which are essentially girdling all limbs, and these trees frequently also get a double whammy of bacterial leaf scorch to help speed them along in their decline.
At some point in time, you'll probably have to have this tree removed. Replace it with something other than another pin oak - maybe a member of the white oak group.

Oh no! I was hoping it wasn't something fatal. What a huge bummer!!!! Thank you for your help.

So would you think these are caused by the wasp, or by the bacteria?

The wasp.
I need to get out and shoot some photos of some of the pin oaks around here - many have these galls the entire length of every branch & limb - causing the branches to droop even more than is characteristic for pin oak.
Once they get to that point, then we start seeing epicormic shoots popping out at odd spots on the main trunk, and when I see that, it's a good indication that the tree is on its way out.

Nice example of the dangers of planting too much of the same thing!

Lucky, get your mind out of the gutter! Horned or gouty (not horny!!!) oak galls, two very similar galls formed by related Callirhytis wasps. They are even worse up here on shingle oak, and can be found in serioous numbers on black oak and cherrybark oak. These might be the only two frequently fatal galls out of many hundreds that affect oaks.

Guy S.

I hope this isn't too dumb of a question, I know next to nothing about gardening (though, I am trying to learn), but why is this fatal?

Well, the short answer is: because it kills the host tree!
Hee-hee-hee!

The longer answer has to do with the stem girdling that the gall does over time. It has a multi-year, two phase life cycle and is basically impossible to cure, so your best bets are to try to keep your trees vigorous and to avoid planting shingle, pin or other susceptible oaks where the galls are present. And it takes a long time to build up enough galls to kill a tree, so even if you have a few galls don't expect the tree to die tomorrow.

Guy S.

I've never seen any of these galls, but if someone found them only on a couple of branches should they prune them out?

Couldn't hurt; might help. But once they find you, it's an uphill battle.

Guy S.