Carpenter ants? - Ask Extension
There is a constant area of sawdust-like frass on our deck below a high limb of a silver maple tree. The tree is otherwise healthy, although this summ...
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Carpenter ants? #909898
Asked July 15, 2025, 9:38 AM EDT
There is a constant area of sawdust-like frass on our deck below a high limb of a silver maple tree. The tree is otherwise healthy, although this summer there has also been a constant accumulation of brown leaves in general under it- tree is full of green leaves. Ideas as to what this/these are?
Montgomery County Maryland
Expert Response
We can't tell if the sawdust-like residue is from Carpenter Ants, wood-boring insects (often beetle larvae), or another source. Carpenter Ants would rarely, if ever, be responsible for significant dieback in a live tree; they excavate dead wood and prefer wood that is already compromised by water damage (for indoor structures) or decay.
We also can't see enough detail in the photos to tell what is contributing to leaf drop, but that is normal for a variety of causes, including anthracnose. Anthracnose is prevalent this year due to the wet weather pattern that ended last year's drought for most areas earlier this season. No fungicide treatment is needed (nor would it reverse any existing infection) for the tree, but as to the wood shavings, you can have it evaluated by a certified arborist or licensed tree expert to determine if any damage of concern is being done. Arborists can also look for sources of tree stress, like girdling roots (which can be common with maples), which might be able to be alleviated.
Miri
We also can't see enough detail in the photos to tell what is contributing to leaf drop, but that is normal for a variety of causes, including anthracnose. Anthracnose is prevalent this year due to the wet weather pattern that ended last year's drought for most areas earlier this season. No fungicide treatment is needed (nor would it reverse any existing infection) for the tree, but as to the wood shavings, you can have it evaluated by a certified arborist or licensed tree expert to determine if any damage of concern is being done. Arborists can also look for sources of tree stress, like girdling roots (which can be common with maples), which might be able to be alleviated.
Miri
Thank you for your reply!
Actually it turns out the dead leaves are coming from a large-ish branch that seems to have got stuck on its way down from falling in a recent storm- it’s not endangering anything so we can wait it out.
Meantime I wonder if wood boring insects are a danger to the tree? The sawdust is very localized and look to be coming from under a 12-15 inch diameter stub of a branch that was cut back by tree workers to keep it from growing too close/over the house.
On Jul 15, 2025, at 1:27 PM, Ask Extension wrote:
You're welcome.
If possible, have the storm-broken branch pruned by a professional, as jagged/torn wood can lead to wood decay hollowing-out that branch stub and potentially progressing into trunk wood.
It depends on the wood-boring insect. Some tunnel in dead wood, some tunnel in live wood, so the latter group would be more of a threat to tree health. That said, many target trees that are already stressed or in decline, but not exclusively. If the sawdust is emanating from a stub of dead wood, then it's probably not concerning, aside from the fact that stubs should not be left on any removed limbs save for a very, very short section of wood left to make sure the cut isn't damaging the branch collar tissue. It might not hurt to also have a professional take a look at that and correct any improper pruning, at the very least before the decaying wood fails and it falls.
Miri
If possible, have the storm-broken branch pruned by a professional, as jagged/torn wood can lead to wood decay hollowing-out that branch stub and potentially progressing into trunk wood.
It depends on the wood-boring insect. Some tunnel in dead wood, some tunnel in live wood, so the latter group would be more of a threat to tree health. That said, many target trees that are already stressed or in decline, but not exclusively. If the sawdust is emanating from a stub of dead wood, then it's probably not concerning, aside from the fact that stubs should not be left on any removed limbs save for a very, very short section of wood left to make sure the cut isn't damaging the branch collar tissue. It might not hurt to also have a professional take a look at that and correct any improper pruning, at the very least before the decaying wood fails and it falls.
Miri
