Hot Topics: Getting Rid of Carpenter Ants

A close-up image of a caprenter ant.

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Original Post: carpenter ants

dm888 Member

I noticed a lot of carpenter ants moving around my deck last year (it's Trex), and then saw them around an area of the siding on the house so I think they were in there. I sprayed some Ortho Home Defense in that area and later saw there were a bunch of dead ones. Surprisingly after that, I don't think I saw an ant on the deck the rest of the summer. Do they really just move on if they are disrupted like that?

Anyway, they were back again yesterday in a different location from last year as I noticed a few inside the house and then saw a bunch of them around the door out to the deck. Again, I sprayed the Home Defense inside along the baseboards and outside along the wall and even under the deck. There were a couple dead ones inside later on, but I haven't seen anymore.

I want to do a more thorough job this year with the bugs. I do see the occasional spider in the house (probably more often than I should) so I was wondering if there is a better spray or something else I should be using to keep the ants away (and spiders, too, if possible) or is that Home Defense adequate? Is my best bet to spray the entire perimeter of the house with something every so often?

PJmax Group Moderator

They won't touch Trex, but they will go after the framing. If you are seeing them where the deck joins the house, it sounds like you have a water penetration problem. They like to follow water and they will....right into your house.

Marq1 Member

Home Defense is pretty good for normal bugs. The key is to use it on a regular basis to keep it potent vs. a one-time application when you find something. However, carpenter ants are around because there is something rotting that they have found. I've had them a couple of times and with some investigation found the bad area. You just need to spend some time and follow them; they will lead you!
PAbugman Forum Topic Moderator
The active ingredient fipronil is outstanding on ants and termites. It can be found in various brand names such as Termidor, Taurus, Fuse, and probably some others. These are concentrates that are mixed with water. Labeled directions call for exterior treatment only with some exception. It's a non-repellent, which is key to its success. If you choose to use fipronil, then don't use any other insecticide unless you know that it's non-repellent. Ortho home defense is a repellent.

Carpenter ant colonies expand until they get large and then a "satellite" colony breaks off. New queen(s) take a cross section of workers with them and overnight there will be a new colony in or around your house. A likely scenario is a mature colony is in a tree nearby and broke off a satellite colonly. If you choose to use fipronil, then I would spray the bottom three to four feet of tree trunks that are close to your house, if any.

Fipronil isn't great for spiders, but I'd focus on the ants first as the good spider sprays will be repellent. If you are seeing live ant activity, then now would be a good time to start. Two to three times a year of fipronil should be adequate. You can work in spider sprays in between. The fipronil will help with the spiders so it may be enough, but if someone was hiring me, I wouldn't use it for spiders.
dm888 Member
Since I already sprayed Ortho, will that make the fipronil less effective, or will that wear off soon? I actually haven't seen any ants since that first day, but they must be somewhere. I do have a couple of big trees that are about 50 feet away and a few smaller ones closer, so I could spray the trunks like you said. In addition, if the Ortho didn't hurt anything, would you recommend spraying the perimeter too and maybe around every post of the deck? Basically, any means that they could enter the deck or house?

I looked up the difference between repellent and non-repellent sprays so I can see why the non-repellent is so effective. How much time in between can you go before using a different type? You're right—the spiders aren't a huge problem. There are actually stink bugs that seem to be more of a problem that I forgot to mention.
PAbugman Forum Topic Moderator
I'd wait four weeks and six at the most before using the fipronil again and the same when switching chemicals. Basically, spray a low and high perimeter, with high meaning up to soffits. If you can't reach that far from the ground, try leaning out a window and spraying.
dm888 Member
I have not seen an ant since about three weeks ago when I had some in the house and saw them outside the door and sprayed the Home Defense. Do you think I even need to get the fipronil, or should I just thoroughly spray the entire perimeter with Home Defense since it seemed to work and has in the past?
PAbugman Forum Topic Moderator
I know I wouldn't use anything but fipronil on ants on the exterior; as a preventive or as a cure as it is so effective and safe that it's a no-brainer. Our industry went to non-repellent sprays for ants for a reason. Fipronil is not labeled for indoor use, but Phantom is, and it's a non-repellent that's effective on ants.