July 14, 2012

1 - Ants falling from trees may indicate carpenter ants, or they may be species of ants that do not damage the integrity of the wood of the tree.

We just moved here and we are concerned about our Cottonwood tree AND OUR HOME!! It seems there might be an infestation of maybe carpenter ants in the tree. They are falling down to the ground by the THOUSANDS! We do not want to lose the tree, it is the only HUGE one we have and we are worried about the house too. Do you have any advice?

Gwen E.

Via NMSU University-wide Extension


Without seeing the ants, I cannot be certain that they are carpenter ants, but they are a possibility. However, they may be another type of ant as well. Ants are often drawn to trees that have aphids feeding on the sap of the tree. The ants collect the sugary honeydew excreted by the aphids for food. They also protect the aphids from predators that would otherwise help you manage the aphid population. If this is the case, the tree will suffer only minor damage from the aphids. You can often manage aphids and ants by washing the aphids from the tree periodically with a strong jet of water. You may not be able to reach all the aphids and ants with this treatment, but that should help reduce the problem. If aphids are present in the tree, you will also notice a fine mist of the honeydew collecting on the ground and on other surfaces under the tree. The water will help wash away this sticky honeydew.

If the problem is really carpenter ants, they may be infesting the wood of the tree. This is not uncommon and can severely weaken the tree. They make their residence in tunnels cut through old, often rotting, wood in the tree. They are rarely found in the living wood essential to maintaining the health of leaves and roots, but they can weaken the integrity of the tree trunk, increasing the probability that the trunk will break and the tree will do damage as it falls. Years ago, Dr. Charles Ward, former NMSU Extension Entomologist, told me that the carpenter ants rarely infest wood in houses unless that wood has been damaged by water and begun to decompose. Under those conditions, the ants may enter structural wood and cause damage to homes.

It would be wise to contact your local NMSU Cooperative Extension Service agent and have the ants identified to determine if they are carpenter ants or not. If carpenter ants are identified, the Extension Service agent can advise you as to treatment procedures and whether or not the tree will be a hazard to structures and people if the tree should fall. If there are signs of infestation in your home, a professional pest control company should be consulted. Such companies often provide free inspections and estimates. Ask several companies to inspect your home and provide bids.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


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