Why ants invade your home after rain, and how to stop them

If you've ever found a trail of ants across the kitchen bench the morning after a downpour, you're not alone. Heavy rain floods nests in the soil, and ants move to somewhere drier, bringing their queens, eggs and larvae with them. Your walls, cavities and pantry are ideal.

Where they get in

Ants are tiny and can use almost any gap: around window and door frames, along pipes and cables, through cracks in mortar and slabs, and under skirting boards. They follow invisible scent trails laid by the first ants that found food or water, which is why one ant quickly becomes hundreds.

What helps

• Wipe trails with warm soapy water or a vinegar solution to remove the scent trail.
• Store food in sealed containers and wipe benches before bed, including sugary spills and pet food.
• Fix leaks and dry wet areas under sinks and in the bathroom.
• Seal visible gaps around frames, pipes and cables.
• Trim plants and branches touching the house, which act as bridges.
• Use ant baits where ants are trailing, and give them time to work.

What can make it worse

Spraying the trail with a household insect spray kills the workers you can see, but not the queens or the nest, and it can stop ants taking bait back to the colony. With some species it can even cause the colony to split into several new nests. If you're using baits, don't spray around them.

A note on fire ants

Red imported fire ants are a serious biosecurity pest and must be reported in NSW. If you notice small, aggressive, reddish-brown ants and dome-shaped mounds of loose soil with no obvious entry hole, don't disturb them. Report them to the NSW Department of Primary Industries.

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