Husker Hort

A Nebraska View of Horticulture

Carpenter Ants: the misunderstood ant

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Carpenter ants are one insect that are often misunderstood. They are an important part in the circle of life in decaying wood. Knowing a little more about these insects will help to understand why they are in a specific location and whether or not it might be possible to control them.

Knowing a little more about the foe will give you an idea of what to expect. Carpenter ants make their tunnels and burrows in dead and decaying wood. Their mouthparts are used to ‘chisel’ the wood into the tunnels. They do not feed on the wood, they just take advantage of it for their home. Carpenter ants normally feed on insects, aphid honeydew, sweets, meat and fats. The workers leave the colony late in the afternoon or early in the evening, forage during the night, then return to the colony in the early morning hours. There are two common species of carpenter ants in Nebraska. The black carpenter ant is a large, black ant about 1/4-3/8” long. The second ant is the ‘red’ carpenter ant, it has both red and black body parts, and is slightly smaller than the black carpenter ant. Carpenter ants can even have wings. When a colony gets very large, it produces offspring with wings that splits off of the colony in search of other nesting sites.

Carpenter ant nest in the rotting heartwood of a tree.

Where you see the carpenter ants makes a difference in how you control them. The ants prefer moist or partially decaying wood. If you see carpenter ants on a tree, it is a good indication that tree has internal rot. Inside the home, the ants often indicate rot within wooden parts of the structure, like rotting wood under a rain gutter, leaky window, or around the plumbing in the house. The best time to see carpenter ants inside the structure is at night when they are foraging in the evening. Look for big ants that are just wandering around aimlessly.

Control of carpenter ants indoors is often difficult. The bait stations are not very successful due to the varied diet of the carpenter ants. Over the counter sprays are also not extremely effective because only some of the workers will die, the colony will be unaffected by the sprays. Your best bet is to work with a pest professional to help find and treat the colony. Together you can locate the colony and use the right product for the location to kill the entire colony.

Controlling carpenter ants in a tree branch or trunk will only help with part of the issue. You can kill the ants using an insecticide dust containing carbaryl or permethrin, but that is not helping with the larger issue, the tree. Some species of trees are really poor at compartmentalizing and stopping/slowing the spread of rot in the heartwood of the tree. Hackberry and silver maple are two examples of trees that don’t do a good job slowing the spread of rot fungus once it gets started in an area within the tree. When a limb is removed from one of these trees, we often see the rot begin to work on the internal wood of the tree before the outer tissue has an opportunity to seal over the wound, leading to hollowed out or rotted sections.

Rather than thinking of carpenter ants as the problem in the tree, consider them an indicator. If you see carpenter ants on the tree, take the time to inspect the tree for internal rot. Look for areas that didn’t have a chance to seal over at an old branch wound or look for areas with holes where moisture would collect. The tough part is once internal rot is started within the tree, there isn’t an application that can be made to slow the spread or correct the issue. The tree won’t get any better and the rot will continue to spread within the heartwood of the tree. Contact a certified arborist to come out and help inspect the tree to see if there are indications the extent of the internal rot within the tree.

Take advantage of nature’s little recyclers, they could be indicating potential problem for you down the road.

Elizabeth Exstrom is the Horticulture Extension Educator with Nebraska Extension in Hall County. For more information contact Elizabeth at, her blog at, or HuskerHort on Facebook and Twitter.

Author: Elizabeth Exstrom

A Nebraska Extension Educator out of Hall County with a focus in horticulture and sustainable landscapes.

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