Ants are social insects forming colonies underground, in logs, wall cavities or in the base of potted plants. They prefer dry and freely draining soils. The introduced Argentine ant, Linepithema humilis, is a major pest species. Argentine ants are a light brown, comparatively slow moving species up to 3mm long.
Tunnelling in potted plants displaces potting mix, exposes delicate feeder roots and increases the risk of plants wilting. Worker ants actively farm aphids, scale insects and mealybug, moving these insects to new host plants. They often defend these pests from predators and may build tunnels to move them around. Ants are most active repairing tunnels after rain and swarm during warm weather.
- Water potted plants thoroughly soaking all the compost or stand potted plants in a bucket of water;
- Daily disturbance of colony entrances, especially after rain;
- Pour boiling water into colony entries in cracks in paving and brickwork. Avoid using near plants roots;
- Stand potted plants in soapy water deep enough to inundate all of the potting mix. Allow to stand for 24 hours. Rinse delicate plants, such as ferns, in clean water to remove traces of soap;
- Prepare a bait mixing honey or syrup with borax to create a runny paste. Place bait in the bottom of a narrow-necked bottle, such as an old chilli sauce or Worcestershire sauce bottle. Lay bottle on its side near ant colonies and cover lightly with mulch or old leaves. Worker ants collect the bait and feed it to the colony, controlling numbers. If the queen ant/s is/are killed the colony dies.
Borax is a:
- stomach poison;
- household cleaning agent;
Caution: do not use borax baits where young children use the garden.