I’ve got a young burr oak in the front yard. It’s about 8’ tall and has a trunk about 3" in diameter at the base. Also at the base is the excavation work of a colony of ants. They’re black, and somewhere between 1/8" and 1/4" in size. I see many of them routinely climbing up the tree and investigating branches and leaves. I assume they’re looking for other insects to take as prey, but I haven’t witnessed that, nor have I seen them physically harming the tree.
However, from the looks of them, they seem to be carpenter ants (I could take and post some pictures if that would help). Normally I’d expect them to be chewing out an old stump or a much larger tree, but they’re here at the base of my favorite little oak. Should I worry? Are they actually carving out the heartwood of such a small tree? Will their underground excavation disrupt root development? The tree isn’t showing any signs of stress, but I certainly don’t want it damaged. On the other hand, I don’t want to needlessly kill a colony if they’re not doing any harm.
If ants are crawling into a tree they are almost certainly feeding on and protecting some sort of sap-sucking insects. The insects they are taking as prey will mostly be other predators such as lacewings or ladybirds. That alone won’t kill the tree, but it will inhibit growth and make it more prone to diseases that can kill it. Ants are much more likely to be harming your tree than helping it.
The excavation won;t harm the roots, however it will make the root zone dry. On a small tree this can place considerable stress on the plant.
Ants probably won’t kill a tree. If it’s under stress for other reasons, the outcome may be different. However, if you’re worried about the ants, there are simple solutions that I can recommend because they’ve worked for me. Go here:
Some ants will move aphids around as the leaves the aphids ‘eat’ are depleted (usually the tenderish younger leaves, ime). If the aphids are present, then there is tree damage happening, for sure.
Aphids are the tiny (hardly visible by eye) sap-sucking bugs that are treated kind of like cows by some types of ants. The ants will move the aphids around the tree(s) to increase productivity, and also keep other predators from harming the aphids. The aphids give off a sticky (sweet??) discharge that ants love, so the ants milk the bugs by rubbing their antennae on ‘em…or something like that. Aphids are bad for trees’ health (if not already obvious).
Yeah, I’ve got aphids on a honeysuckle vine. Oddly enough, no ants there. I’ve been releasing ladybird beetles and spraying them down with a hose to combat them. I haven’t seen any aphids on the oak tree though. I will take a closer look later today.
Regardless, it’s sounding like I probably should temporarily abandon my “Live and let live” motto and take a “Better safe than sorry” approach and get rid of the ants. Thanks for the advice all and the link oliversarmy.
According to my wife, if your tree has some rotted wood, the ants will eat that, and that’s beneficial to the tree. I haven’t tried Googling that to verify it.