The presence of ants in a lawn often sparks immediate concern for homeowners, leading to the assumption that these insects are directly consuming the turf. However, the relationship between ants and grass health is more nuanced than simple herbivory. Ants cause significant, visible damage to a lawn, but this is due to the structural consequence of their tunneling and nesting activities, not direct consumption.
The Direct Answer Do Ants Consume Grass
The definitive answer to whether ants eat grass is largely no, as the vast majority of lawn-dwelling ants are not herbivores. Their dietary needs are met by foraging for proteins and sugars, not by chewing on grass blades or roots. Common ant species primarily feed on dead insects, seeds, and honeydew, a sugary excretion produced by sap-feeding pests like aphids and mealybugs.
Living grass is not a preferred food source because its composition does not offer the nutrients they seek. Specialized species like leafcutter ants harvest plant material, including grass, but only to cultivate a fungus garden that serves as their actual food source. Ants may also carry off seeds from newly seeded lawns, which are a concentrated food source, but they do not consume established grass plants.
Indirect Damage Caused by Nesting Activity
The true source of lawn destruction comes from the physical act of ants building and maintaining their complex underground colonies. This nesting activity involves extensive tunneling and the excavation of soil, which is then deposited on the surface as characteristic mounds or anthills. These mounds can range from small, barely noticeable piles to larger structures depending on the species.
The most immediate damage comes from the excavated soil mounds that smother the grass directly beneath and around them, preventing sunlight and air from reaching the blades. This smothering effect creates unsightly bare or yellowing patches in the lawn. Below the surface, the extensive network of tunnels disrupts the soil structure, creating air pockets that expose the grass roots. This exposure causes the roots to dry out rapidly, leading to eventual plant death, which manifests as brown, dead spots in the turf.
Identifying Damaging Ant Species
While many common ants, such as pavement ants, generally cause only minor surface disruption, certain species are notorious for the scale and severity of the damage they inflict. The most significant threat comes from mound-builders like imported fire ants and field ants. Fire ants create dome-shaped mounds that lack a central opening, and their nests aggressively kill the underlying grass roots, leading to large, distinct dead patches.
Field ants also build large mounds that destroy the grass root structure. Another problematic group includes species like Argentine ants, which harm the lawn indirectly by “farming” mealybugs for their honeydew. This encourages the proliferation of sap-feeding pests that actively damage the grass. Identifying the specific type of ant is helpful because the scale of the damage and the control methods required vary greatly between species.
Remediation and Prevention
Addressing an ant problem in the lawn involves a two-part strategy: controlling the ant population and repairing the resulting turf damage. For minor, localized issues, simply raking or brushing away the visible soil mounds when they are dry can redistribute the soil and prevent smothering without killing the colony. This action levels the surface and encourages the grass to grow back through the disturbed soil.
For larger or more persistent infestations, especially those involving fire ants or field ants, direct treatment is usually necessary. Targeted treatments are preferred over broad-spectrum lawn applications to minimize impact on the environment and beneficial insects. Ant baits are an effective control method because worker ants carry the toxic substance back to the colony, killing the queen. For severe cases, a liquid or granular insecticide applied directly to the mound may be used, though these should be applied judiciously and according to label instructions. Once the ant activity is controlled, the bare spots should be raked, top-dressed with fresh soil, and reseeded to promote new turf growth.