Carpenter ants can be a sign of a bigger problem

Iowa State University
Moist and decaying wood make an ideal habitat for these large ants.

Among the largest ants commonly found in Iowa, the “carpenter ant” is usually considered the most destructive.

Varying in lengths of 1/4 inch to 3/4 inch, these pesky insects are best known for what they destroy – not what they build.

In a recent publication called “Carpenter Ants and Their Control,” Donald Lewis, professor and extension entomologist with Iowa State University Extension and Outreach, explains how to identify and control these ants.

Carpenter ants chew into wood in order to build tunnels and cavities for nesting. They prefer soft and decaying wood and are commonly found inside stumps, hollow trees, landscaping timbers, roofs, decks and fence posts.

“If found outside, the carpenter ant may not be an issue, but if you start seeing them indoors or you see an unexplained accumulation of sawdust, you may need to investigate,” said Lewis.

Although these ants can cause extensive damage, more damage is often caused by the moisture intrusion and softening of the wood that invited the ants in the first place.

Treatment options include do-it-yourself products that can be applied to ant nests or, if nests cannot be found, room edges, cracks and crevices. Commercial options are also available, depending on the severity of the infestation.

Lewis notes that finding a carpenter ant in the home does not necessarily mean the ant lives in the home or that there is an infestation. The ant may have escaped a piece of firewood or is coming indoors for warmer weather, or for food scraps.

On the flipside, he says ants that are causing damage do not always leave a trail in open sight. The damage could be in the dark places of the attic or in the basement – wherever moist wood is present.

Tips for prevention

  • Correct moisture problems such as a leaky roof or plumbing, poorly attached flashing and sagging rain gutters.
  • Ventilate crawl spaces to reduce wood decay.
  • Replace rotted, water-damaged wood within the structure.
  • Eliminate wood-to-ground contacts that lead to wood rot of lower siding boards and sill plates.
  • Remove dead stumps and trees. Remove board piles and old firewood.
  • Store firewood off the ground and away from the house.
  • Trim trees and shrubs that touch the house.
  • Patch and seal points of entry such as cracks and gaps in the foundation, loose-fitting windows, doors and shrunken, loose caulking.