All of a sudden, we have little dark ants in our family room. They seem to be coming in around the patio door, even though it’s kept closed. I also see ants on the shrubs outside the door so I guess that’s where they’re coming from. How do I keep them out? P. T., Uxbridge, MA

If you can determine that the ants are coming in from outside, that’s a good thing. At least you know they are not nesting in your home. Controlling them outside should be easier than controlling them inside. In fact, you may have found the source of your problem — your foundation shrubs.

I bet if you look closely at those shrubs, you will see aphids or some other plant-feeding insects such as mealybugs, whiteflies, or scale insects. These tiny insects have piercing mouthparts that they use to suck juices from plants. They will be clustered along the stem or on the underside of leaves.

Ants and Aphids Have a Special Relationship

Aphids are known for the sticky, sweet fluid called “honeydew” that comes out of their rear end after feeding on plants. Many ants crave this sweet liquid and will protect aphids and even milk them to get the honeydew droplets that they exude (see Why Ants Herd Aphid “Cows”). When you see ants on plants, they’re usually there because of aphids.

All of that would be fine if the ants stayed only on the plants. However, sometimes the ants will forage randomly and end up in your house instead. Ants also leave the plants if the aphids leave the plants for some reason. If the plants are touching your house, the ants then have an easy pathway to move inside. Sometimes, we even see indoor ant problems that can be traced to a houseplant that is infested with aphids, scale insects or mealybugs (see The Ant/Houseplant Connection).

In certain cases, an indoor ant problem can be resolved by simply spraying outside plants to kill aphids. Your plants will thank you, too. Once ants lose their aphid food source, they will forage elsewhere. Doing some pest-proofing or sealing around your doors and windows and pruning back foundation plants will help keep the ants from foraging into your home. Give Colonial Pest a call. If necessary, we can keep those ants out of your house by applying a preventive barrier around the foundation. We do pest-proofing, too!

Photo Credit : “Ant guards its Aphids” by viamoi | CC BY 2.0 via Wikimedia Commons.