Seeing ants crawling on plants often leads to the assumption that they are consuming the foliage, flowers, or fruit. While some species occasionally cause direct damage, their presence is usually a symptom of a larger, more destructive issue in the garden. Controlling an ant problem requires understanding this root cause and implementing a strategic, two-pronged approach: protecting the immediate plant and eliminating the colony source. This guide provides actionable steps to remove ants from your garden and prevent their return.
Determining Why Ants Are on Your Plants
The primary reason ants are found on plants is not to eat the foliage but to collect a sweet, sticky substance called honeydew. Honeydew is the sugary waste product excreted by certain sap-sucking insects, such as aphids, mealybugs, and scale insects, as they feed on the plant’s vascular tissue. These pests must consume large amounts of plant sap to extract enough protein, leaving them with an excess of sugar they excrete.
Ants have developed a symbiotic relationship with these pests, often referred to as “farming” or “herding” them for their honeydew. The ants stroke the abdomens of the aphids with their antennae, which encourages the release of a honeydew droplet the ant then consumes. In return for this high-energy food source, the ants aggressively protect the honeydew producers from natural predators, including ladybugs and parasitic wasps.
This protection allows the pest populations to explode, and their unchecked feeding is what causes the true damage to your plants, leading to stunted growth, distorted leaves, and the spread of plant viruses. Therefore, seeing a trail of ants on a plant is a strong indication that an infestation of sap-sucking pests is already established.
Immediate Non-Pesticide Plant Protection
The first step in controlling the problem is to protect the immediate plant by removing the honeydew-producing pests without using harsh chemicals. A strong, focused jet of water from a garden hose can physically dislodge most soft-bodied pests like aphids and mealybugs from the stems and undersides of leaves. Since many of these pests reproduce quickly, repeating this water treatment every few days is often necessary to significantly reduce their numbers and prevent a rapid population rebound.
For a more thorough treatment, horticultural soap or neem oil can be applied directly to the affected plant parts, ensuring full coverage, especially on the underside of leaves where pests often hide. Horticultural soap works by dissolving the protective outer layer of soft-bodied insects, while neem oil acts as an insect growth regulator and repellent. These products are considered safer for the environment and beneficial insects than broad-spectrum insecticides.
To create a physical barrier that stops the ants from reaching the pests, a sticky material can be applied around the base of the plant or container. Products like Tanglefoot create a band that ants cannot cross, effectively cutting off their access to the honeydew source. This barrier immediately disrupts the ant-pest mutualism, making the pests vulnerable to natural predation or subsequent treatment.
Eliminating the Ant Colony Source
Eliminating the entire ant colony is the most effective long-term solution to stop the foraging and farming behavior. The most strategic method for colony elimination is the use of slow-acting insecticidal baits, which are available in liquid, gel, or granular formulations. These baits are designed to be attractive to worker ants, who consume the material and carry it back to the nest to share with the queen and larvae through a process called trophallaxis.
Unlike direct-kill sprays that only eliminate the foraging workers, a slow-acting bait allows the poison to be distributed throughout the colony, ultimately killing the egg-laying queen and collapsing the nest structure. The bait should be placed near the ant trails or nest entrances, but never directly on the plant or in the path of beneficial insects. It is important to use a protein or sugar-based bait that matches the nutritional needs of the specific ant species being targeted.
Alternatively, for smaller, localized ant nests found in the soil near a plant, direct treatment can be considered. Pouring boiling water directly into the nest entrance can destroy a significant portion of the colony, including the queen, if the nest is shallow and accessible. Diatomaceous earth, a fine powder made of fossilized diatoms, can also be dusted near nest entrances and ant trails, where it physically damages the ants’ exoskeletons as they walk over it, causing dehydration.
Long-Term Garden Management for Prevention
Preventing future ant problems relies on establishing garden practices that discourage the presence of honeydew-producing pests. Regular inspection of plants, particularly new growth and the undersides of leaves, allows for the early detection and removal of small pest populations before ants discover them. Promptly pruning away heavily infested plant parts can also help contain a localized outbreak.
Maintaining a clean garden environment is necessary, as ants are attracted to various food sources beyond honeydew. Removing fallen fruit, dead leaves, and general debris eliminates potential nesting sites and foraging opportunities for the ants. This practice also denies the pests shelter and minimizes the chance of fungal growth, like sooty mold, which can grow on honeydew residue.
Encouraging a diverse ecosystem that includes natural predators will provide a sustainable, long-term biological defense against the pests that attract ants. Ladybugs, lacewings, and hoverflies are highly effective predators of aphids and other soft-bodied insects. Planting a variety of flowering plants that provide pollen and nectar will help support and maintain a healthy population of these beneficial insects in your garden.