Ant hills appearing in a lawn are a common nuisance for homeowners, prompting a search for fast, simple solutions. The most intuitive response is often to grab a hose or bucket and attempt to flood the colony. Pouring plain cold water into the opening of the nest seems like a logical way to eliminate the problem, leading many to wonder if this simple act of drowning the ants is truly an effective method for colony removal.
The Efficacy of Drowning
Pouring cold water into an ant hill is generally an ineffective method for long-term colony elimination. This failure is due to the complex, deep architecture of the subterranean nest structure. While the surface mound may seem small, the full colony often extends over a foot deep, and tunnels in some species can reach depths of several feet.
Ants are highly adapted to survive natural flooding events, having developed several survival mechanisms. The colony can quickly relocate the queen and the delicate brood (eggs and larvae) to higher, drier chambers within the complex network of tunnels. Water poured into the opening tends to drain away through the surrounding soil and passages rather than filling the entire nest cavity.
Certain species, such as fire ants, can collectively link their bodies together to form a buoyant, waterproof raft. This raft floats on the water’s surface, protecting the queen and brood until they reach dry land. This collective behavior allows a significant portion of the colony to survive for extended periods. Cold water alone typically results only in a temporary disruption, with surviving ants rebuilding a new mound nearby within a few days.
Alternative Water-Based Elimination Methods
Water can be an effective control agent when its properties are altered to increase lethality. One method with a higher success rate is the application of boiling water, which kills a large percentage of the ants it contacts. The heat from water near 200°F (93°C) or higher is enough to kill ants instantly and can penetrate deep enough to reach the queen, who is often situated in a chamber deep below the surface.
To apply this method, pour several gallons of boiling water slowly and directly onto the mound’s opening. This technique is most effective when a large portion of the colony is near the surface, such as on a cool, sunny day when ants move closer to the exterior for warmth. A significant drawback is the high risk of killing surrounding grass and plants, as the intense heat destroys the root systems of any vegetation it touches.
A second, less damaging water-based approach involves using soapy water. Adding liquid dish soap introduces surfactants that break down the water’s natural tension. This allows the water to penetrate the ant’s waxy, protective exoskeleton, clogging the spiracles (the small holes ants use for breathing). The soap mixture effectively drowns the ants by coating them and causing suffocation, rather than relying on physically flooding the entire nest structure.
Non-Water Control Methods
For the most reliable and lasting results, non-water methods that target the entire colony, including the queen, are necessary. The most widely recommended approach is the use of insecticidal baits, which eliminate the colony from the inside. Baits consist of a slow-acting poison mixed with an attractive food source, such as sugar or fat.
Worker ants forage for this bait and carry it back to the nest, sharing it with the rest of the colony, including the queen and developing brood, through a process called trophallaxis. Because the poison is slow-acting, the foraging ants have time to distribute the toxic material throughout the colony before they die, ensuring the death of the queen and the cessation of egg production. Baits should be positioned near ant trails or the mound entrance, but never directly into the hole, to allow efficient transport back to the nest.
Another effective non-water option involves the application of insecticidal dusts or granules. Diatomaceous Earth (DE) is a popular natural product that works by physical action rather than chemical toxicity. DE is composed of finely ground fossilized aquatic organisms; its microscopic sharp edges scratch the ant’s protective cuticle. This damage causes the ant’s body moisture to rapidly evaporate, leading to dehydration and death.
Chemical dusts work on contact, poisoning the ants as they walk through the material. Both DE and insecticidal dusts should be lightly dusted around the entrance of the nest and along the ant trails. The goal is for the worker ants to track the material into the nest on their bodies, where it can affect other colony members. These dusts act as both a barrier and a direct control method for ants moving on the surface.