By Jeff Rugg- Q: Our landscape has been invaded by ants. Actually, the ants aren’t out in the landscape but instead are in all the flowerpots on the patio, in between the patio bricks, in the shed, on the tree trunk next to the patio and, unfortunately, coming in the kitchen.
We don’t see any out in the garden or lawn. Bait traps seem to be starting to work, but it is hard to tell. Why are they suddenly taking over the patio but not the yard?
Most of the potting soil in the flowerpots is the same brand as always, and most of the flowers are ones we have planted in the past. Some of the ants are big, and some are small. Are they different kinds, or will the small ones grow up to be bigger ones?
A: Many landscapes are having a problem with ants and some other ground-dwelling insects this spring. The areas hit hardest by flooding don’t have many ants, worms and other ground-dwelling insects, for these animals either drowned or floated over to higher ground.
Areas that haven’t flooded but remain very wet have the same problem, as the soil has been too wet for these animals to live in. Even chipmunks, groundhogs and other ground-dwelling animals have moved to higher ground.
Homes and other buildings are built on the higher portion of any landscape to create drainage for rainwater away from said buildings. Your patio is part of the higher ground. Flowerpots on the patio provide shelter for insects that need soil.
The ants will forage for food in any dry area they can find, including indoors. Ants can travel more than 100 feet from a colony.
Ant bait traps can work well, but they need to be monitored to see if the bait is gone or not. Bait works best when it is carried back to the colony. Some ant colonies have multiple queens, so placing the traps all the way around the house may be necessary. Contact insecticides only kill ants that are exposed, so ants in the colony that aren’t hit will continue to reproduce.
Spraying around the base of the home with an insecticide treatment for ants and termites may be beneficial. Check the insecticide label to see if it lists ants.
Once the soil dries out, the ants will find more food in the landscape than between the patio bricks and will then move back into the landscape.
The ants you see are full-sized adults, so there are different kinds in your landscape. Larger carpenter ants that have been living in a rotting log may move to a tree or building if the area around the log is flooded. They can divide their colony and set up in firewood piles or even a dead tree limb.
These ants are not especially harmful to most trees; they merely remove the soft, rotting wood that already exists. Something else caused damage to the tree, and decay is breaking down the cellulose, which the ants then remove. Once in the tree, the colony is protected and difficult to treat. Apply a powder or dust version of an insecticide that mentions carpenter ants on its label into as much of the tree cavity as possible, as well as around the base of the tree.
Don’t try to plug the hole in the tree or apply tree paint of any kind. These materials will just seal in the microorganisms and promote more decay. It is possible the tree needs to be removed because the decay has hollowed it out, but this is probably not because of the ants. A licensed arborist will be better able to diagnose the potential hazards the tree presents.
Email questions to Jeff Rugg at firstname.lastname@example.org.