Ants are social insects that are found all over the world and encompass thousands of species. Relatives of bees and wasps, they live in organised colonies consisting of fertile females (queens), sterile males and workers, and carry out specific tasks. The role of queens is to establish new colonies and lay eggs, whereas the only function of males is to mate with the queen ants, after which they quickly die. By contrast, worker ants’ responsibilities include defending the nest, supplying it with food, and feeding the queen and larvae.
Here in Italy, among the most widespread species are the acrobat ant (Crematogaster scutellaris), red ant (Formica rufa), black ant (Lasius niger), Argentine ant (Linepithema humile) and pavement ant (Tetramorium caespitum).
Up to a point, the presence of ants in the garden and vegetable patch can be tolerated. It’s a different story, however, if the colony expands to become a full-scale invasion: in this article, we will talk about the damage that these insects can cause, before explaining how to get rid of them.
How ants can damage the garden and vegetable patch
Ants are omnivorous, which means that they feed on whatever is available in the surrounding environment, whether that be seeds, animal and vegetable remains, honeydew or household foods (which is why you can even find them inside kitchen cabinets and in rubbish bins). They leave the nest to hunt for food from spring until the arrival of the colder months.
Ants can cause both direct and indirect damage. Many feed on seeds, which they steal from freshly sown soil and store in their nest. In the vegetable patch and on trees they eat strawberries, potatoes, ripe fruit and so on. They have a symbiotic relationship with colonies of aphids, which are small insects that suck sap and excrete honeydew, a sugary substance that attracts ants: this is why you see them climbing in lines on vegetation infested with aphids.
While the aphids invade and damage plants, including both ornamental and fruiting varieties, ants defend them against predators—such as aggressive ladybirds—in order to safeguard their food source. Other honeydew-secreting insects that proliferate thanks to ants include mealybugs and psyllids. Honeydew also settles on leaves to form a sticky coating that promotes the growth of sooty mould, a fungal disease.
On the other hand, ants play a key role in the ecosystem of gardens and vegetable patches. Together with other insects, small animals and the various plant species, they contribute to biodiversity by helping to create a balanced environment—including in terms of insect/predator dynamics—in which every element has its own function. Ants aerate the ground by digging tunnels, eliminate harmful insects (such as processionary moth caterpillars), clean up dead plants and animals, and even help to pollinate flowers.
Remedies against ants
Are there natural remedies against ants? You can try solutions that deter them without resorting to man-made products. These insects use chemical signals (pheromones) to guide their movements and communicate with each other, leaving behind a scent trail that is identified and followed by their nestmates. So, to eliminate ants in the garden and vegetable patch you can take advantage of plants and substances that have a smell which ants find unappealing or irritating, or which masks the scent trails they leave behind.
Natural ant repellents include garlic, wormwood, lavender, marjoram, mint and tansy. Except for garlic, all of these plants can be used as borders for your vegetable patch, around the various sections, and along garden flower beds and surrounding plants. To eliminate ants, you can spray plants with strong-smelling, self-produced macerates such as garlic, wormwood—both of which are also effective against aphids—or mint.
You can prevent ants from moving around, reaching aphids on plants or following their usual trails by creating “barriers” made with dry crushed rue leaves, powdered chilli pepper, coffee grounds, chalk or ash. You can also use lithothamnium, a calcareous flour obtained from a particular type of marine algae. Apply glue traps or fly paper to shrub stems and tree trunks.
As we have said, the presence of ants is linked to aphids. Another remedy against ants therefore consists of targeting the aphids with repellents (such as garlic and nettle macerates) or insecticides (such as pyrethrin and neem oil). Here you will find more information on how to recognise and eradicate aphids and many other plant parasites.
As long as they are not overrunning the vegetable patch, as we said, ants can be tolerated. If, on the other hand, you are getting overwhelmed by these tireless workers, we advise eliminating the ants once and for all with natural insecticides such as pyrethrin or diatomaceous earth (sand consisting of the fossilised remains of microalgae). Pyrethrin is also effective against aphids, but has a broad spectrum of activity and therefore also kills beneficial insects such as bees (so it should not be sprayed on plants while they are flowering). Also consider that eliminating worker ants only partially solves the problem, because the queen will continue laying eggs back in the nest.
You can work out the position of the nest by observing the ants’ movements: usually nests are built below ground level, under stones or similar objects, between cracks in the pavement, and so on. Shortening grass with a brushcutter or lawnmower, as well as removing piles of dry leaves and removing mulch, can make them easier to spot. Another possible remedy for keeping ants away is by moving the nest with the aim of drawing the insects elsewhere.
If you prefer to protect and strengthen your greenery using substances of natural origin and active plant ingredients rather than with synthetic products, here are some other natural treatments for plants. Insects aren’t the only undesirable visitors to gardens: in this article you will find remedies for getting rid of moles.