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How to Get Rid of Carpenter Ants in Trees

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Spotting carpenter ants in your trees is not just a sign that your tree is in trouble, but could mean that nearby structures are in danger of infestation. Left untreated, these little insects can lead to big trouble, especially if they make their way to your home. Thankfully, finding and eradicating carpenter ants from your trees is a process you can handle on your own.

The only way to permanently rid yourself of carpenter ants is to locate and eradicate their nest. Once you’ve found the nest, you can apply the right kind of insecticide based on your unique situation. In this article, we’ll break down how to find the nest and how best to apply the insecticide to be sure the infestation doesn’t return.

carpenter ants in tree

Signs You Have Carpenter Ants in Your Trees

Carpenter ants get their name because they build their nests in wood using their mandibles to chew out tunnels, usually targeting damp or decaying wood. Unlike termites, carpenter ants do not eat the wood; they only chew it down to dust to clear out space for their nest.

Below are a few common signs that you might have a carpenter ant infestation:

  • Ant Activity—The most obvious sign of an infestation is spotting a swarm of ants. The ants will appear to move in and out of the soil at the base of the tree, which is another indicator that they are nesting and not just passing by.
  • Dying or Decaying Trees—Carpenter ants prefer to build their nests in unhealthy trees where the wood is softer and easier to chew. Inspecting your trees frequently is one of the easiest ways to identify a possible infestation.
  • Tree Holes—Oftentimes, carpenter ants will enter the tree using existing holes created by birds, other insects, or natural damage. Any trees with large, visible holes would be a preferred target for carpenter ants and are a good place to start your inspection.
  • Dead Limbs—As the ants burrow deeper into the tree, they can start to cause individual branches or limbs to die. Spotting dying limbs while the surrounding branches appear healthy could be a sign that the ants have started to nest inside.
  • Sawdust Piles—As carpenter ants chew the wood, they leave behind piles of a sawdust-like material. These piles are most likely to accumulate under or around the existing holes in the tree as the ants clear more space for their nest. When inspecting any holes in the tree, it is a good idea to search for sawdust or wood residue in and around the hole.

Finding the Source of Your Tree Infestation

So, you’ve seen a sign of a possible carpenter ant infestation in your trees. Now what? As mentioned, the only way to be sure you’ve gotten rid of your carpenter ants is to find and eliminate the source, or the parent colony. This is the primary nest and will be located in the damp and decaying wood.

Infestations that have gone untreated for some time can grow, leading to the development of satellite colonies of carpenter ants.

While the queen and most of the workers will be found in the primary colony, satellite colonies are home to pupae and larvae which, left untreated, can not only cause the infestation to return but also lead to the invasion of nearby structures.

You may be able to find the nest simply by identifying the hole the carpenter ants are using to enter and exit the tree. Many times, it won’t be as obvious, so take an earth scraper and probe around the base of the tree looking for soft spots. If you uncover a space with a frenzy of ant activity, you have likely found the nest.

Using Bait

Sometimes, you may notice the ant activity away from the tree. Following the path of the ants could lead you directly to a primary or satellite colony.

Carpenter ants love sugary and protein-rich foods, and if found, will carry it back to their queen or larvae. If you’re struggling to identify the nest or want to be sure you’ve found any satellite colonies, leave out some bait such as a small sweet or mealworm, and follow the course of the ants carrying it.

How to Choose the Right Ant Insecticide

Now that you have located the infestation, you will need to thoroughly apply an effective insecticide to eradicate the colony. The best insecticide to use will depend on whether or not you’re sure you’ve identified the source of your infestation and all potential colonies, as well as your personal preference for treatment.

There are four main types of insecticides you can use to rid your trees of carpenter ants.

Liquid Insecticides

A liquid insecticide can be sprayed directly onto the nest to poison the ants, making it the easiest and most efficient solution. When applying, you first want to target the nest directly, or the suspected entry point, and spray thoroughly until completely soaked. You also want to target other entry points and spray other visible holes on the tree.

Since the poison can be transported by the ants, you’ll also want to target their pathways around the trees. Look for any lines of activity away from the tree and thoroughly cover with insecticide. As a final step, spray the entire base of the tree, starting from the bottom and working your way up, ensuring that you’ve fully coated as much area as possible.

Dust Insecticides

Dust is also an effective insecticide option. This option works similarly to the liquid insecticide and can also be transported by the ants as they carry it back into the nest.

Dust can sometimes be a cheaper insecticide option and can have a longer residual life than liquid insecticide, particularly when used inside of dry and covered spaces such as internal holes. The dust also can be easier to track, ensuring you have adequately covered all necessary areas.

Bait Insecticide

Commercial ant baits are an extremely effective option that can target any type of ant infestation. Since the ants will bring the bait directly to the nest and satellite colonies, even if you have not identified these sources yourself, baits are often seen as the best long-term solution.

The drawback of bait insecticides is that they can take time to work, as you are depending on the ants for delivery. You must also be sure not to use a bait insecticide that is meant to lure the ants along with another insecticide that repels the ants, as this will render each insecticide useless.

Natural Alternatives

While chemical insecticides are both safe and effective, many people prefer a more natural option. The most common alternative is peppermint essential oil, as carpenter ants are repelled by peppermint. Another common option is cedar oil, which is extremely dehydrating to the ants and will cause them to suffocate.

While these natural alternatives may work, they tend not to be as effective as more industrial insecticides and require more reapplication until the problem is under control.

Continued Monitoring

Remember that carpenter ants do not cause the initial decay to the trees, they just take advantage of it. That means even if you have eradicated them for the moment, you need to continue to monitor the health of your trees for any signs of new infestations. A little extra care now might save you a lot of work later.

Keep watch for any of the initial signs of a possible infestation and, if spotted, repeat the process until no further signs appear. 

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Jena Slocum Co-Founder

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  1. Hello. I have a hole in a base of tree a few feet above the ground in a tree wound. Ants are going in and out of it and there is saw dust at base of tree. Any recommendations for a brand/type of bait/killer that I can spray in amd around hole? Thanks, Chris

    1. Hi, thanks for the comment. We’ve had great success with the Terro brand ant insecticides for inside and outside our house. They make an ant dust that should work around your tree.

  2. What do you do if the colony is high up in a tree and you can’t get to it. Last fall I had a nest that was living in some leaves that were on my roof and I suspect that they came with some leaves that fell off of the tree. I got rid of them and that took care of the ants that were getting in my house for a while. I have a line of ants that are going up and down the tree, I can’t see where they are going cause its a tall tree and I can only see so far up. I have baited but I never see them really taking it (i use advion gel bait), should i just continue doing that with some ant dust or should I just spray the base of the tree with insecticide?

    1. Thanks for the comment. If it was me, I would call in a pest control company since it’s an odd situation. You may be able to talk to someone about it before they come out just to verify how they would handle it.

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