Rotten Holes on the Tops of Live Oak Branches

[WillClimb]

What do you guys do when you get big pocket holes on the top-side of Live Oak branches (or other trees)? I've seen a lot of them on unworked trees and they're some pretty nice branches otherwise...branches that I'd like to save.

The problem is that they collect water like a cup, and then start decaying and rotting off the whole branch. I've read that you can use that expanding spray-foam that is used in construction, or fill the holes with concrete, but I'd rather here from those who practice this art, rather that those who write about it.

Thanks - Will Allen

 

[Treeman14]

First of all, you must determine what caused the cavities to form in the first place. Something happened which allowed decay-causing pathogens to enter the branch. The three most common causes I've seen for the type of wound you describe are; 1.)Repeated topping/tipping/sucker removal by utility contractors, 2.)Improper pruning, i.e. flush cuts, or 3.)Squirrels chewing on the bark.

Whatever the reason, the water which collects in these cavities is NOT the cause of the decay. The decay-causing pathogens will do their job regardless of whether the cavity is wet or dry. In fact, the water may inhibit the action of these aerobic pathogens. If the tree is otherwise healthy, its own natural defenses will limit the spread of decay, especially on a live oak. Problems arise when we try to "help" the tree by drilling drain holes or filling cavities. Any action which destroys the tree's protection zones will increase the spread of decay.

I believe the best course of action in this situation is to do nothing which will disrupt the natural boundaries already established by the tree. If there is doubt as to the strength of the limb, perhaps some drop-crotch pruning is advisable to lighten the load. Or a cable might be installed to help support the limb. I know a lot of arborists have been using the expandable foam lately, but I don't think it has any benefits for the tree. Of course, the treatment chosen will depend on the results of a thorough hazard evaluation.

 

[WillClimb]

Well, I know pretty much for sure what has caused these holes. It's where an old branch was broken by a storm or something and a stub was left....about the same as topping the branch, I would guess. Anyway, it appears that the tree tries to heal the stub but decay finally reaches down past the cambium layer of the host branch and the stub eventually falls off. Then water and dirt fill the hole.
And so, you're saying that the water and dirt are not bad for the branch, or are you just saying that they're not the original cause of the decay? And yes, I know that dirt and water are two things a tree needs. I just assumed that on top of a branch they were bad.
Every time I pull an old bird's nest or squirrel's nest out of a tree I can see the damage that it's done by collecting water and making a nice environment for bugs.

 

[John Paul Sanborn]

The dirt is mostly the residue of the decayed stub, think of the side branch as being plugged into a sockett in the main branch. the compartmentalization is going on around the this area. there is a natural protection zone there. If you feel that the cavity is large enough to reduce the strenght of the limb, maybe thinning the tip out to reduce wieght is a solution. Never worked live oak, but I see it alot in bur's. Decay in red oak gives me a little mor concern, they dont comaprtmetalize as well as the whites, but then I see it in silver maple and box elder too. Now that will make me want to do something coerrective

 

[WillClimb]

Thanks you guys....that's good stuff.