Carpenter Ants in Urban Trees


Carpenter ants are very common in urban trees as are the myth about these secretive insects. The abundance of these insects in urban settings is due to their lack of available nesting sites as compared to a forest. People put ant infestations in their homes at the same level as termite. To clear one thing up ants live in wood as termites eat and digest wood.

Due to there common occurrence in urban trees and there potential damage to homes we as arborist are asked what to do with these insects. Ants exhibit diversity in size and appearance within a species and there are over 900 species of ants ranging in size, and colour.

A carpenter ant colony forms two types of nests. The main nest (one with the queen) is located in decayed or moist wood however the potential for expansion to un-decayed wood still exists. The nest is usually in contact with the ground or near a source of moisture.

Carpenter ants form satellite nests in locations that are drier and warmer to raise the mature larva. This may not mean you have a water problem in your house as the nest may be in a stump or tree in close proximity to your home and the ants have access to your home through tree branches touching your house or your utility lines.

A few ants on your trees doesn’t mean it is infested however it is a good indicator that the nest is either in that tree or close by.

One thing to look out for in the spring is the ants with the wings in swarms as they are mating and every fertilized female is looking for a new location to start off its new nest.

Carpenter ants have been viewed by arborists as beneficial as they indicate rot in your trees. However their presence in our trees close to houses is a source of potential infestation from either the dispersal of a colony or by forming a satellite nest. Carpenter ants are also beneficial as they can be important predators during outbreaks of defoliating caterpillars. They recycle wood back into the forest. They are a great source of food for many birds (ex Pileated woodpeckers another major sign of carpenter ant infestations)

Management techniques include: removing several decayed trees around your property including grinding of all stumps after removal, disposing of all buried wood and wood lying around. Fixing leaks around your home, limiting access to structures is a good idea as well. This includes building and line clearance and removing shrubs from around the base of your home. Chemical treatment or baiting is also an option however this will not solve the problem just postpone it.