Carpenter ants are among the largest and most noticeable ant species found in Australia. Unlike termites, they do not consume wood for food, but they do tunnel into timber to build nests, which can lead to structural weakening over time. Understanding their biology, behaviour, and the right prevention measures is essential for maintaining healthy homes and buildings in Melbourne’s climate.

Identification

Carpenter ants belong to the genus Camponotus, which includes several species found across Australia. Worker ants range from 6 to 12 mm in length, while queens can reach up to 18 mm. They are typically black or reddish-brown with a rounded thorax and strong mandibles. These ants prefer moist or decaying wood, commonly nesting in tree stumps, logs, fence posts, or structural timber exposed to damp conditions. Indoors, they may establish nests in wall cavities, window frames, or roof spaces where wood has softened due to moisture.

Carpenter ants are mostly nocturnal foragers, feeding on sweet substances such as nectar, honeydew from aphids, and household sugars. They also consume insects and plant juices but rarely damage solid wood for food. Instead, they excavate wood to create smooth tunnels for nesting, which can weaken structures over time. Colonies grow slowly but can survive for many years, eventually housing thousands of workers in well-established nests.

Threats

Carpenter ants pose a structural threat due to their nesting habits. They excavate smooth tunnels inside timber, weakening beams, frames, and flooring — especially in damp or untreated wood. Though they don’t eat wood like termites, long-term infestations can cause sawdust-like frass, faint rustling in walls, and hollow-sounding timber. Older homes with leaks or moisture damage are most at risk.

They may also expand into insulation, electrical conduits, or foam panels, leading to inefficiency or occasional short circuits. Outdoor nests near sheds or power poles can spread indoors if conditions are suitable. While not a health risk, their presence indicates moisture or decay, often requiring both pest control and minor repairs.

In gardens, carpenter ants act as scavengers and predators but can disturb the natural balance by outcompeting other insects and protecting honeydew-producing pests such as aphids.

Preventions

Prevention focuses on removing moisture and decayed wood, as sprays alone don’t reach colonies. Repair leaks in roofs and plumbing, replace or treat rotting timber, and trim vegetation that touches the house. Seal gaps around doors, windows, vents, and foundations, and ensure roof voids or crawl spaces are dry and well-ventilated.

Keep firewood and timber piles off the ground and away from walls, and store sweet or greasy foods in sealed containers. Remove old stumps, logs, and garden waste that attract nesting ants.

For infestations, professional pest control is recommended. Experts locate and treat the parent colony using slow-acting bait systems or targeted dust formulations. Advanced tools such as thermal imaging and moisture meters help detect hidden nests and ensure complete eradication.

Summary

Carpenter ants are part of Australia’s ecosystem but can cause serious issues when nesting in damp wood. Managing moisture, maintaining sound timber, and seeking professional inspection when early signs appear are key to preventing costly damage. Gill Pestworks helps Melbourne residents protect their homes through proactive pest management and prevention.