Weed killer (herbicide) is not an effective or recommended solution for controlling ants. Herbicides are specifically formulated to target and disrupt the biological processes unique to plants, not insects. Using these chemicals against ants is an off-label application that yields poor results for pest control and introduces unnecessary health and environmental hazards. Effective ant control requires a product designed to exploit the social and physiological vulnerabilities of the insect itself.
Why Herbicides Are Not Designed to Kill Insects
The fundamental reason herbicides fail to kill ants lies in the vast difference between plant and insect biology. Herbicides interfere with specific pathways plants use for growth and survival, pathways that are absent or significantly different in insects. For instance, glyphosate targets the shikimate pathway in plants, which is necessary to synthesize essential amino acids. Blocking this pathway starves the plant, leading to death.
Insects, including ants, do not possess the shikimate pathway, meaning they are largely unaffected by this mechanism of action. Insecticides, in contrast, are specifically engineered to disrupt the insect’s nervous system, often by interfering with critical enzymes or neurotransmitter receptors. These nerve and muscle poisons result in rapid paralysis and death, a mechanism fundamentally different from the slow, metabolic disruption caused by most herbicides.
Health and Environmental Hazards of Misuse
Applying a chemical designed for weeds directly to an ant nest or trail constitutes a misuse that carries serious health and environmental risks. Herbicides are not registered or tested for use as insecticides, meaning their safety profile for this specific application is unknown. When large amounts of herbicide are dumped into an ant mound, the chemical persists in the soil and can be tracked indoors by pets or children, increasing the risk of contact exposure.
This misuse also contributes to broader environmental contamination. Herbicides can move through the soil, potentially leaching into groundwater or running off into surface water bodies, which negatively impacts aquatic ecosystems. Furthermore, broad-spectrum chemical application in the garden or yard can harm beneficial non-target organisms, such as earthworms and pollinators like bees.
Proper Methods for Ant Eradication
The most effective and targeted approach to ant eradication leverages the insect’s natural social behavior. Ant baits are superior to sprays because they exploit a process called trophallaxis, which is the mouth-to-mouth sharing of food within the colony. Baits consist of an attractive food element—like sugar, protein, or fat, depending on the ant species’ preference—combined with a slow-acting insecticide.
Worker ants consume the bait and carry it back to the nest, where they distribute it to the queen, larvae, and other worker ants. The insecticide is designed to work slowly, ensuring the toxicant is widely shared throughout the colony before the foraging ants die. This targeted delivery system is the only reliable way to eliminate the colony’s queen, which stops egg production and ensures the permanent collapse of the entire nest, typically within one to two weeks.
Other Eradication Methods
Other methods include applying diatomaceous earth, a natural powder made of fossilized algae that kills ants by physically damaging their outer protective layer. Liquid barrier sprays can also be used for perimeter defense to prevent entry into a structure.