How to keep ants outside

Each year we have larger black ants in the cottage. How do I get rid of them? Is there any way to prevent them from coming inside in the first place?

—David Patterson

It sounds like your intruders are carpenter ants, the largest of the ants you’ll often get in cottage country. They tunnel into wood to make their nests, especially damp, decayed wood, which is easier to excavate. First, the bad news: The nest may be inside your cottage. Look for small deposits of sawdust (evidence of their tunneling) or a high concentration of ants in one spot. To locate the nest, search for ant evidence anywhere there is damp wood and moisture—around the sink and dishwasher, for example, or near leaky door and window frames.

Now, the (sort of) good news: The nest may be outside, in a tree stump or woodpile. Carpenter ants travel up to 100 yards from home to forage, so it’s possible they’re coming inside merely to hit up your kitchen. In any case, a simple solution is to spread liquid ant killer across the paths where you see the ants travel; they’ll pick up the bait and take it back to the colony, where they’ll share it with the rest of the gang. (FYI: Carpenter ants tend to ignore those round bait traps that work with other ants.)

To deter the ants from marching on in to your cottage in the first place, get rid of indoor dampness and nearby outdoor standing water; store firewood outside—somewhere dry, away from the soil; cut back tree branches or shrubs that touch the cottage; keep the kitchen clean and store food in tightly sealed containers; and, if possible, repair cracks or holes where ants can get in.

Eventually, carpenter ants will excavate into dry, undamaged wood—a real problem if they start remodelling inside all the major structural beams of your cottage. So if your DIY methods aren’t working, don’t wait too long before you call an exterminator.