Ants are a common sight in gardens, where they can be both beneficial and bothersome. While some ant species help aerate the soil and prey on garden pests, others become a nuisance by damaging plants or creating large nests that disturb root systems. When ant populations become excessive, they can interfere with garden health and even “farm” other harmful insects. Implementing safe and targeted control measures is necessary to manage these populations without harming plants or beneficial insects.
Why Ants Are Present in Your Garden
Ants establish themselves in a garden primarily because it offers a reliable source of food, water, and shelter. Their main culinary motivation is sugar, obtained from plant nectar, fallen fruit, or honeydew. Honeydew is the sticky waste product excreted by sap-sucking insects like aphids, mealybugs, and scale insects.
The presence of ants is often a sign of a larger pest issue due to a unique symbiotic relationship. Ants actively protect these sap-sucking pests from natural predators, such as ladybugs and parasitic wasps, in exchange for the honeydew they produce. They will even “herd” the aphids, moving them to new plant growth to ensure a continuous food supply. Ants also seek dry, sheltered locations for nesting, sometimes building extensive tunnels around plant roots that deprive plants of moisture and nutrients.
Immediate Non-Lethal Control Techniques
Immediate control focuses on deterring ants and disrupting their foraging trails without introducing lethal agents into the environment. Ants rely heavily on pheromone trails to communicate and navigate, so breaking these paths can effectively confuse and redirect them.
A simple, non-toxic approach involves using strongly scented substances to mask the pheromones. A solution of equal parts white vinegar and water, or a spray made from diluted peppermint or citrus essential oils, can be applied directly to ant trails and nest entrances. Strong spices like cinnamon or cayenne pepper also serve as deterrents; sprinkling a thin line of ground cinnamon around vulnerable plants or trails can block access.
Physical barriers protect individual plants, especially trees and shrubs, from ants climbing up to access pests. Applying sticky tree bands or a thick paste of petroleum jelly around the trunk creates an impassable obstacle. For container plants, a water moat can be created by placing the pot legs in a shallow dish of water, preventing ants from crossing. Shallow nests can also be temporarily disrupted by flooding them with a strong stream of water from a hose.
Eliminating the Colony with Targeted Agents
For a persistent ant issue, eliminating the colony is necessary, which requires a slow-acting, targeted agent that the ants will carry back to the nest. Baiting systems are the most effective way to reach the queen and the rest of the colony, as the foraging ants ingest the agent and share it through a process called trophallaxis.
A homemade bait can be created using a mixture of borax or boric acid combined with a sugary attractant like sugar or honey. A ratio of approximately one part borax to six parts sugar is suggested, as this concentration is weak enough for the ants to carry it back to the nest before they die. Place these baits in enclosed, pet-safe containers, such as lidded jars or bottle caps, and never apply the mixture directly to the soil, as borax can act as an herbicide and harm plants.
Another targeted method involves using food-grade Diatomaceous Earth (DE), a fine powder made from fossilized diatoms. This material works as a mechanical insecticide; the microscopic, sharp edges of the silica particles scratch the ant’s waxy outer layer, causing the insect to lose moisture and die from desiccation. For maximum effectiveness, DE must be applied as a dry, thin dusting to ant trails or nest entrances, as it loses its abrasive quality when wet. Always ensure the product is labeled as food-grade, as pool-grade DE is chemically treated and toxic.
Cultural Practices for Long-Term Deterrence
Long-term ant control relies on modifying the garden environment to make it less appealing for both nesting and foraging. Since ants are attracted to sap-sucking pests, maintaining plant vigor through proper watering and balanced fertilization helps plants naturally resist infestations.
Controlling moisture and debris also discourages ant nesting in unwanted areas. Ants prefer dry soil for their colonies, so consistent, deep watering can make the ground less hospitable near vulnerable plants. Regularly removing organic debris, such as fallen fruit, wood piles, and leaf litter, eliminates potential nesting sites and easy food sources. Pruning tree and shrub branches away from structures, fences, and the ground removes “ant bridges” used to access plants or enter buildings.