The Tapinoma Magnum, a “very invasive ant that makes everyday life difficult”

In recent years, a new species of ants has ruined the lives of around 200 houses in a district of the city of Saumur (Maine-et-Loire). This invasive alien species, called Tapinoma Magnum, multiplied again this summer thanks to the high temperatures. Who are these insects and can we defeat them? The point with a specialist, Loïc Bidault, elected for ecology, sustainable development and energy transition in the city of Saumur, who also holds the post of vice-president of the Conservatory of Natural Spaces of the Pays-de-la-Loire.

Loïc Bidault, elected ecologist of the city of Saumur and vice-president of the Conservatory of Natural Areas of the Pays-de-la-Loire. – Loïc Bidault

Can you show us those? Tapinoma Magmum ?

It is a Mediterranean species, more specifically Corsican, which then arrived in southern France. It has been with us in Saumur for three to six years now, but we really identified it last year, after protests from residents and with the help of scientists from the Institute for Research on Insect Biology (Irbi) from Tours. It is believed to have arrived by transporting ornamental plants, often surrounded by clods of earth, perhaps with the fashion for olive or palm trees coming from all over the Mediterranean. Scientists also make the connection to global warming because they find that we have environments that are welcoming. It is a species with a very particular behavior, very invasive and associated with strong inconveniences.

This means?

The ant Tapinoma Magnum lives in super colonies. They spread particularly quickly, without competing with other anthills. We can spot them with the naked eye because they are very small and have extremely sociable, hyperactive behavior. They are found mainly on degraded land, cuttings. But there are also large numbers of them in the gardens: they swarm everywhere and if you go outside they climb on you. A lady confided in me that her grandchildren stopped coming to her house in the summer because of this! They don’t bite but have a very invasive side. Another special feature, when crushed, they give off a smell of rancid butter…

And they do damage too…

Yes, especially in vegetable gardens we have seen zucchini or young tree seedlings fully infested. In fact, these species that do not have predators create a vacuum around them: in the sectors where the Tapinoma Magnum prosperous, our classic ant threatens to disappear in the next few years. Thanks to the pipes, cables, they are also introduced into the houses… We had electricity meters that turned on for some residents! This makes everyday life difficult for some of those affected. Last year it got to a significant level, people were completely helpless, so we had to propose a scientific and structured approach with a lot of education.

What can we do against these ants?

Once the species is identified, it must be treated immediately. Which we couldn’t do fast enough here with a meanwhile 18-hectare area and the presence of these ants in two cemeteries. Scientists tell us we can’t eradicate it, so let’s contain it, we limit it as much as possible. We have decided to provide financial support over three years in order to carry out three treatments per year on the affected people. We treat public spaces every 15 days from March to September with a spinosad-based product that can be used biologically. The results are quite positive.

That Tapinoma Magnum » seems to be gaining ground in France, especially in the West…

Saumur acts as a laboratory for all of France and I regularly receive calls from local authorities to ask how we are doing. It is therefore clear that we will speak again about this ant, here but also elsewhere, and in particular in the Loire Valley or in Loire-Atlantique where it was identified, for example, in Ancenis. We’ll see how the species evolves, there may be surprises. There is a village near Pau where the ant disappeared for no reason one summer… fingers crossed it happens to us! There is also a possibility that another invasive species will arrive and displace it. Meanwhile, the temperature drop should offer us a period of calm until March.

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