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 Sunday, May 24, 2015
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My neighbors are worried about seeing large half inch long, black ants on their trees and even in their homes.  How damaging are they and do they kill trees?


I feel fairly sure that you are speaking about a carpenter ant.  These ants are normally found in wooded areas where there are a lot of decaying stumps, rotting roots and/or old declining trees.  These sites are perfect for them to build a nest.  Carpenter ants live in colonies made up of a “queen”, males, workers, eggs, and pupae.  The colony can be discovered by the discarded wood chips (frass) piled on the ground near the entrance to the nest.  The colony supports a large home nest (normally outdoors), plus several satellite nests.  To destroy the ant colony, all nests must be found and taken out. 


This type of ant, associated with dead and rotting wood, do not eat the wood and do not cause the rot.  They will not kill your trees.  They just prefer the soft moist rotten wood in which to build their nurseries.  Indoors, they seek out areas around plumbing and roof leads.  Out of doors, they seek rotting stumps and roots, decaying trees, and firewood.  Carpenter ants eat dead and living insects, the honey dew emitted by aphids, juices, ripe fruit, sugar and sweets, and scraps of food.  Generally, when you see a single ant, it is a scout foraging for food.  When he finds food, he will leave a pheromone scent trail back to the nest.


Up to a point, carpenter ants have a positive effect on the environment, in that, as a scavenger, they reprocess or clean up rotting wood.  On the other hand, when their tunnels put a strain on the tree’s water conducting capacity and when the tunnels weaken the tree’s structure and the tree becomes a hazard tree, then ants become unwanted pests.


To get rid of the ants, as mentioned earlier, it is essential to destroy both the home and satellite nests.  Aside from finding and destroying the nests, trimming trees back five feet from any building structure to eliminate pathways into the house will help.  In eliminating stumps, cover and storing firewood away from the house and off the ground, and repair roof and plumbing leaks also helps.  Proper food storage and sanitation can reduce ants.  You should wash areas that have been used by foraging ants in order to get rid of the pheromone scent trail.


Every year there are fewer and fewer chemical products allowed to be used by the non licensed homeowner.  A few will be available at the hardware or garden center.  Read the directions carefully.  Boric acid is one material that is still available, it will kill foraging ants but it will not be carried back to the nest.  Liquid formulations are also available such as Deltamethrin, Permethrin, Pyrethrin and Tralomethrin.  Aerosol sprays do not give long lasting ant control.  Bait cups do not work on carpenter ants because they have such a wide diet.  But, if you must, use sugary or honey based bait.  If you see large amount of ants indoors (twelve or more in one day) and you suspect a heavy infestation, call a professional exterminator.  They are licensed to use stronger, longer-lasting pesticides not available to the general public.


Be sure and let your neighbors know that for the most part, carpenter ants are not nearly as bad as they are thought to be.


David Hubbard

Regional Extension Agent

Alabama Cooperative Extension System

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