Tree Appears Healthy, But Ants Up and Down Trunk


Well-Known Member
United States
This is actually a tree at my house, not for a customer.

I’ve climbed it many times over for fun. Blooms nice wood seems solid.

I went for a rec climb this evening and noticed ants up and down the trunk. Don’t see any holes or cavities or anything just ants crawling.

Could this be nothing or a sign of something more problematic? I know they can get in there and do damage but from what I saw I didn’t notice anything immediate that stood out as a sign of damage. But I didn’t do a complete top to bottom inspection and the sun was starting to set so didn’t see whole tree.

Here’s a pic of a few ants (there are more) and of just the trunk itself so you can see what it looks like.

Kind of dark out to get a good pic of whole tree. Just to be clear, there are many more ants up and down trunk.

1C18D17D-93AE-4351-AD52-97013CE23D6F.jpeg C8CA57BB-2B50-48F8-9AEA-938FF8DA8F8A.jpeg
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Well-Known Member
Have been observing some trees in my area with way worse ant trails up and down the bark for about eight years thinking they would decline as there are other variables stressing the trees - yet they are surviving and even prospering.

Wouldn’t be concerned.


Well-Known Member
They do, but they don’t eat living wood, if I recall correctly. Ants are often a symptom of a problem, not the actual problem. Woodpeckers are the same way, they’re looking for bugs, which are either a problem or a symptom of the problem.
You are on the right track. Here is my understanding. Symptom and sign are closely related but different. I believe ants are a sign of possible decay.


Well-Known Member
Also possible they are gathering nectar, bud scale juices, or farming aphids,.. Is there a nest in the tree or a trail leading away.
I like Evo's notion. So much goes on about which we are unaware!
As for carpenter ants, they excavate dead wood (an preferably a bit decayed) to produce the gallery and trail structure of the colony. Yes, they do chew up large quantities of wood in the process, but they don't gain substantial nutrition from the wood (unlike termites). They do forage on fungal hyphae when they encounter them! Nutritional sources do vary. They do need ready access to moisture.

Yes, they do indicate wood decay is somewhere nearby. Then again, isn't it always?


Well-Known Member
Probably a net-positive effect for the trees. I only see carpenter bees eating up black locusts, and that’s after they’ve fully succumbed to shelf fungus.

From Peter Wohllenben, The Secret Wisdom of Nature, some insight into ants relationship to trees- an excerpt from an entire chapter-

‘The more interesting question is what the overall ant-aphid-forest balance looks like. Science hasn’t come up with a definitive answer, however, most studies conclude that the positive effects generally outweigh the negative ones. John Whittaker at Lancaster University, for example, discovered that, on balance, birches did significantly better when there were ants around. Although ants increase the number of aphids, this was true only for some species. Species of aphids not farmed by ants declined drastically. Furthermore, leaf-eating insects in general declined so significantly that leaf loss was six times less than in birches not settled by ants. According to Whittaker, plane trees also seem to come out mostly ahead. Aphid-farming ants reduce attacks by other plant-eating insects to such an extent that plane trees with ants increase their girth two to three times faster than plane trees that have to manage without the ants’ protection.’


Well-Known Member
I've got a small (4 inch DBH), very healthy swamp white oak that has tons of ants in the spring, but they seem to disappear by July. The posts above explain that. Thanks. I love the collective knowledge of this site.


Well-Known Member
North East
Most of the Black Walnut trees I've taken in my area have had carpenter ants in them.
Tend to hollow out the heart wood.
One tree that I cut a limb off looked like black liquid was pouring out of the cut till I looked closer.
Ants were literately pouring out of the stub.
Thought I struck oil for a second. :D


Well-Known Member
Florida>>> USA
i think we should embrace;
trees as a total marvel of biological machine as the longest living, largest, tallest, most leveraged, most oxygen and carbon production, most water turn over, most rigid plant etc. that because cant move to a better location, has figured out by going along in harmony with Nature(not against) to make a better location; as close to an animal move as this king of the jungle can conspire. Any of the mosts/top contender listed should get notice/an award as top leader, but all these combined into one system, makes the 'unbeatable' tree!
That trees, as many critters, probably did a lot better before our meddlings.
As thinks went along, a bigger saw only allowed to hunt and take down bigger game.
i think the ants are observers, even benefactors of the destruction, but not creators. Shigo model is they are only like vultures in that they clean up the dead and decay, as that is all either eats. Fungals cause rot, removing dead/wet and providing more air holds fungus back i think. Ants are more likely to be stalling, rather than initiating decay; and not known for breaking thru the codit wall previously created. Healthy wood is resistant to micros', not injured wood. Codit walls off damage, ants can help clean up ugly side of wall, competing with more noxious(and wetter) elements to the same prize/food.
Trees changed the planet, keeping the ultraviolent sun rays from barrening/irradiating the planet by providing shade, deflection and even using some of the energy up to crack CO2 byproduct apart into carbon back to the environment that all living forms as we know are based on ; and at the same time rendering O2 that those life forms needed. And doing this en masse like no other plant, when only plants can do such functions.. Without trees inventing (most prolific) organic polymer/macromolecule chain: lignin to prevent rot and stiffen to stand more than 4' high w/o risk of collapsing under own weight and leverages, to then support a much larger solar etc. collecting biomass for conversions, than flat a cross the ground coverage presents/exploits space more efficiently w/only same ground footprint/space taken, world would be/was a much different place, with not enough biodiversity to even come close to getting around to people..
This was all done with ants, not saws as a cohort(iculture).
i think the Lorax would have to decode for us that the trees would vote us as the invaders, not the ants that are part of the bio-function.
Humbling, but true..
Discussion of TREES, ASSOCIATES, and SHIGO (2 CD set) picture
Ants are decay flag and witness, not cause.
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