Ants
Do natural ant remedies actually work?
Which natural ant remedies work in New Zealand homes: borax and sugar bait, vinegar, cinnamon and diatomaceous earth, and why Argentine ants shrug most of them off.
The short answer
Some do, for the right reason. Borax or boric acid mixed weakly into sugar water works because it is slow: worker ants drink it, take it back to the nest and share it, which is the principle behind our ant control. Vinegar, cinnamon, peppermint and coffee grounds only wipe or mask the scent trail for a while. Against an Argentine ant supercolony, no home remedy keeps up.
Borax and sugar: the home remedy that is really a bait
Borax and sugar works for ants because it behaves like a professional bait: the sugar gets it eaten, and the boron in it kills slowly enough that the worker ants get home and pass it on before they die. University of California guidance puts the working strength for borate baits at about 0.5 to 1 percent in sugar water. Above that the bait turns repellent and kills foragers too fast, and the colony stops taking it. It is the same idea as shop-bought ant bait, made at home and kept weak.
Their published home recipe uses boric acid: half a teaspoon of powdered boric acid and nine teaspoons of sugar dissolved in a cup of hot water. Borax carries less boron per gram than boric acid, so it takes roughly half as much again by weight to reach the same strength, and erring weak is safer than erring strong. Soak cotton wool in the mix, put it in a small lidded container with a few holes punched in the side, and set it right on the ant trail.
Expect more ants, not fewer, for the first few days while they recruit to it. Change the bait when it dries out, and leave the trail alone.
At a glance
Natural ant remedies compared
| Remedy | What it does | Reaches the nest? | Best use | Watch out |
|---|---|---|---|---|
| Borax or boric acid in sugar water (weak) | Slow poison the workers drink and share | Yes, if weak enough | Indoor trails of sugar-feeding ants | Too strong and they stop taking it; keep from children and pets |
| Dry borax sprinkled | Kills some ants that walk through it | Rarely | Little | Loose powder on floors where toddlers and pets go |
| Vinegar or soapy water | Wipes away the scent trail | No | Cleaning a bench or entry point | The trail reforms from the same nest |
| Cinnamon, peppermint, coffee grounds | Masks the trail at best | No | None we would rely on | Repelling Argentine ants can spread the nests |
| Diatomaceous earth | Dries out insects that crawl through it | No | Dry outdoor paths, under decks | Useless once wet; avoid breathing the dust |
| Boiling water | Kills the ants it reaches | Partly, shallow nests | A single nest in a path or lawn | Kills plants and lawn; scald risk |
| Baking soda | Nothing measurable | No | None | No evidence it works |
Can you just sprinkle borax?
You can, but it does very little. Dry borax powder is not taken home as food, so the ants that walk through it may die and the nest that sent them carries on. It also leaves a fine powder on floors and benches where a toddler or a dog can get at it. Dissolved in a weak sugar bait is the version that works.
Is borax safe around children and pets?
Borax is not the harmless natural cleaner it is often sold as. It is classified in the European Union as a substance that may damage fertility or an unborn child, and the US National Pesticide Information Center notes that toddlers are most at risk because of hand-to-mouth behaviour, and that pets show much the same signs of poisoning as people, such as vomiting and diarrhoea.
So treat a home-made bait like any poison. Label the container, keep the lid on, place it where a crawling child or a dog cannot reach, wash your hands after handling it, and keep it well away from food preparation areas. If a child swallows it, call the National Poisons Centre on 0800 764 766. For a pet, call your vet or the Animal Poisons Helpline on 0800 869 738, a paid service.
Vinegar, cinnamon, peppermint and coffee: what they really do
Wiping an ant trail with vinegar or soapy water does remove the scent trail the ants follow, which is why the line breaks up straight away. It does nothing to the nest, so the foragers lay a new trail within hours or days. That makes vinegar useful for cleaning a bench or an entry point and useless as a treatment.
Cinnamon, peppermint oil and coffee grounds are said to repel ants, but we have found no good evidence that they do, and in tests on fire ant mounds in the United States cinnamon and coffee grounds did not control the colonies. With Argentine ants there is a further catch: anything that works as a repellent can push the colony to split and move, which is why repellents split the colony just as sprays do.
Diatomaceous earth, boiling water and baking soda
Diatomaceous earth, a powder made from the fossilised shells of tiny algae, kills insects by drying out their outer layer as they crawl through it. It keeps working only while it stays dry and undisturbed, so it suits a dry path, the ground under a deck or the back of a garage, and fails on a damp lawn or anywhere it gets wet. Avoid breathing the dust when you spread it.
Boiling water poured onto a nest kills the ants it reaches. Research on fire ant mounds found it eliminated roughly six mounds in ten, and it kills the lawn and plants it touches, so it is a one-nest tool for paths and paving, not a fix for a supercolony. Baking soda has no evidence behind it as an ant killer. Borax beats it because borax gets eaten and shared.
What natural methods cannot do with Argentine ants
Argentine ant supercolonies span gardens and whole streets, with many queens in many nests that cooperate rather than fight, and in New Zealand they out-compete every other ant species where they establish. A home bait can thin the trail in your kitchen, but it cannot keep pace with a population that refills from next door.
White-footed house ants are hard in a different way: their workers do not pass food on to one another, so a bait reaches far fewer of them and a home-made one rarely makes an impression. If a borax bait has run for two weeks without the numbers dropping, or the trails keep reappearing in new rooms, that is the point to call someone in.
Keeping ants out without any product
The cheapest ant control uses no product at all. Seal the gap the trail comes in through, keep sugar, honey and the pet's biscuits in jars or tubs with tight lids, fix dripping taps and leaks, and wipe benches at night. If they are already inside, start by finding where the ants are getting into the house, because that gap is what you will seal.
Outside, deal with the aphids and scale insects on citrus, roses and hedges, because the honeydew they produce feeds ant colonies all year. Trim plants so they do not touch the walls, and put a sticky barrier band around the trunk of a tree the ants are farming, checking it every week or two so debris does not bridge it.
Questions
Home ant remedy questions
What is the best homemade ant killer?
A weak borax or boric acid bait in sugar water. It works for the same reason professional bait does: it kills slowly, so worker ants get back to the nest and feed it to the colony and the queens. Keep it weak, at about 1 percent or less, put it on the trail in a lidded container, and keep it out of reach of children and pets.
What kills ants permanently?
Nothing does with Argentine ants, whose supercolonies refill a cleared house from the neighbourhood, so there the realistic aim is a house kept clear. For most other ants, baiting the colony and then sealing the entry points and removing honeydew sources ends the problem, and it stays ended until a new colony moves in.
Which is better for killing ants, borax or baking soda?
Borax, clearly. Ants eat borax in a sugar bait and share it, so it reaches the nest. Baking soda has no good evidence behind it as an ant killer at all.
What ratio of borax to sugar kills ants?
Aim weak: about 1 percent or less of the borate in a sugar syrup. The University of California recipe is half a teaspoon of boric acid and nine teaspoons of sugar in a cup of hot water, roughly one part to eighteen. Borax holds less boron than boric acid, so use about half as much again by weight, and if the ants stop feeding on it, make the next batch weaker rather than stronger.
How effective is borax against ants, and how long does it take?
Against sugar-feeding ants on a single trail it can work well. Expect several days before you see fewer ants and a few weeks for a colony to collapse, and expect numbers to rise first while the workers recruit to the bait. If after two weeks the trail is as busy as ever, either the bait is too strong, the ants want protein rather than sugar, or it is a species that home bait will not reach.
What should you never mix with borax?
Keep a borax bait to borax, sugar and warm water. US workplace safety guidance lists strong acids, zirconium and metal salts as incompatible with borax, so do not combine it with other chemicals or cleaners, and never mix or store it in a cup or bottle someone could drink from. If it is swallowed, call the National Poisons Centre on 0800 764 766; if it gets in an eye, rinse it with running water straight away.
If you need someone
When the home remedies are not enough
More advice
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