Filling Hollow in Tree?

[Jager]

I've got a large, old Red Maple about 30' from the front door to my house. At its base the trunk is about 3 feet in diameter. About ten feet off the ground there is a hollow, around 8" at the opening and then opening up inside the trunk to about the size of a misshapen basketball.

The hollow has been there for years, of course, and I've never much given it any thought, other than the time a couple years back where I had to pull an apparently orphaned baby raccoon out of it. But last season a European Hornet queen decided to make it the site of her nest. Throughout the summer and fall there was a constant stream of those big-ass insects coming and going, day and night. After putting five cans of Spectracide spray into the hollow over a couple weeks, and making no apparent dent in their activity, I tipped my hat at their persistence and settled into an uneasy coexistence.

The hollow appears abandoned for this year, so I'm good for now. But I'd just as soon not have bees or hornets make a nest there in the future.

Any advice on what I might fill the hollow with, that would not injure the tree? I'd like to avoid insect infestation, but the absolute highest priority is not compromising the viability of the tree and having it become a hazard, given how close to the house it is. It's otherwise in good health and does a great job of providing shade.

Thanks in advance for any suggestions...

 

[BlackSmith]

Spray foam maybe?

 

[SeanKroll]

How many hornets' nests in how many years?

Leave it be. Filling cavities is antiquated and unhealthy for the tree.

 

[Jager]

How many hornets' nests in how many years?

Leave it be. Filling cavities is antiquated and unhealthy for the tree.

Roger that. I don't disagree. If the tree weren't so close to the house I'd leave it be. But having to walk within about 15' of that nest multiple times a day to where we park our vehicles was... interesting. And because of the proximity to the house, and because European Hornets are active both day and night, we had several inside the house at various times.

Last year was the first and only time they've ever built a nest in that particular hollow. Might be they'll never come back. But we had another hollow in another tree about 100 yards away that hosted a nest every year for many years. I was happy to let them be.


I've thought of spray foam. Or concrete. Or sand. Or attaching some barrier to the opening on the outside of the tree. I just don't know what the least problematic might be.

 

[Cobleskill]

Staple some screen over it?

 

[lxskllr]

Euro hornets are intimidating, but fairly docile. You could do worse. I get them in the eves of my house. My first choice would be to try living with them. If that's impossible, I like the screen idea, perhaps with a caulk bead around it for insurance.

 

[Nutball]

Just don't fill it with cement, it makes a tree cutter's job quite unpleasant if ever it needed to be cut down.

 

[flushcut]

Roger that. I don't disagree. If the tree weren't so close to the house I'd leave it be. But having to walk within about 15' of that nest multiple times a day to where we park our vehicles was... interesting. And because of the proximity to the house, and because European Hornets are active both day and night, we had several inside the house at various times.

Last year was the first and only time they've ever built a nest in that particular hollow. Might be they'll never come back. But we had another hollow in another tree about 100 yards away that hosted a nest every year for many years. I was happy to let them be.


I've thought of spray foam. Or concrete. Or sand. Or attaching some barrier to the opening on the outside of the tree. I just don't know what the least problematic might be.

Do not fill the void. Stapling a screen to keep out wee beasties is about as far as I’d recommend. From what you are describing the cavity doesn’t sound that big in relation to the size of the trunk.
Have a tree company stop out and have a look. It could be worse than you can see or nothing to worry about for a decade or six.
A crown reduction may be beneficial to lessen wind loading if the tree is sound enough. Just because a tree has a hollow doesn’t mean it’s structurally compromised. It comes down to if there are cracks or if decay is present.

 

[CurSedVoyce]

Screen or sheet aluminum works.

 

[Mick!]

As has been said, expanding foam works well.

 

[Ed L]

Just don't fill it with cement, it makes a tree cutter's job quite unpleasant if ever it needed to be cut down.

Very common in years past....sadly a Stihl cutquik ain't worth a damn on wood.

Ed

 

[Maximalist]

When I was sawing this elm tree, a variety of bricks suddenly appeared inside.

 

[Ed L]

Had a 36"+ dbh Hard Maple in front of our house when I was a kid.
Concrete filled trunk and cables holding the branches.
Close enough to the road, the village took it down. They had to have the county remove the trunk with a payloader, took it somewhere to rot as nobody wanted to attempt to cut it....

Ed

 

[Jager]

Thanks for the suggestions, guys.

@Maximalist, that tree with the bricks inside it was nuts!