Hot Topics: Elimination Techniques for Carpenter Ants in Attic

A close-up of ants on wood.

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A DIYer found a few carpenter ants in his attic, and then later noticed a trail of them in his yard. He's now on the defense and asked the forum for their methods of ant elimination and control. Read on to know what you should do the next time ants invade your home!

Original Post: Carpenter Ants Found in Attic

MrCarbon Member

So I was removing attic insulation and found some carpenter ants just hanging out under the insulation (blown-in cellulose). There was a pretty good amount and some were huge! I hit them with some Raid ant killer and got a lot of them, but a lot fled the scene. Later that evening some ants were falling through a ceiling fan while we were in the living room.

Every night I see a long line of them coming from my shed using our hose as a road out to the vast sea of our yard. I didn't give it much thought; I thought it was neat, but not anymore!

I've done some research on carpenter ant control. What are your tried-and-true methods?


They love damp wood. If they seem to be congregating in the shed, check for damp wood. If they're marching in a straight line, lay down a line of peppermint, which they won't want to cross. Is there any damp wood in the attic? Soffits, rake boards? You can spray to kill them and also spray your house foundation, etc. But find out where the nest is. Rotted wood in the yard? Also, pressure treated wood is no guarantee against carpenter ants. They may not eat it, but they will tunnel in it.

tevil Member

I've used TERRO liquid ant bait in the past very successfully. Been fighting small concrete ants this year with it. It seems they've burrowed through where our cinder blocks meet the poured footing and are coming up in a couple places in our lower level. Stuff works great as a combo with other perimeter sprays.

TonyP. Member

First and foremost, don't spray any further as an initial step. A mature carpenter ant colony can have 10,000 ants so random spraying will be ineffective. Beyond that, only 10-15% of the colony is foraging at one time.

What you must do is find the nest and eliminate it. However, carpenter ants maintain a system with a main nest and satellite colonies. The queen is located at the main nest and is supported by the satellites. The main nest is therefore the objective.

I believe the most effective way to eliminate carpenter ants is a combination program focused primarily on baiting. Baiting has two benefits. First, foragers carry the bait back to the nests and share the food. In this way bait can kill foragers and other worker ants. BTW, the remaining ants will eat the dead ones, adding to the kill.

Bait has a second and more important benefit. Follow the foragers carrying the bait to find the nest. Then you can destroy the nest with insecticide.

Two more points. There are two types of bait: sweet and protein. Ants prefer one at a time so you'll need both.

Carpenter ants can travel 100 yards from their nest. You thought seeing the ants was neat so I think you'll find following them with the bait very interesting. Do some research on finding the nest to help. Also, if you have some logs around get rid of them.

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