What you can learn from an ant infestation in a Swiss village

News (EAME)

For many years, the invasive ant species Tapinoma magnum has been spreading in central and northern Europe. It’s suspected this species was introduced from potted plants brought in from the Mediterranean region. These ants look similar to the black garden ant Lasius niger, but unlike this native species, T. magnum can form hectare-sized super colonies with thousands of queens and millions of workers.

In a small village of about 900 citizens in a village near Basel, Switzerland, T. magnum has become a major problem in the last decade. It has been able to flourish because of the recently hot summers, and this species has displaced almost all native ant species. In other words, T. magnum is destroying the local biodiversity.

This species is easy to recognize. When foraging, there are often many more insects than there would be with the normal black garden ant, which move in ant trails that are sometimes up to 1-2 cm wide. Unlike most native ant species, there are different sizes of T. magnum adult worker ants — small, medium and large — ranging in length from 2-5 mm. By contrast, the European black garden ant does not have this variety.

Incidentally, when crushed, T. magnum ants can smell like rancid butter. The workers feed mostly on the sugar-rich feces of aphids by trophobiosis, but also enter houses in search of food. Many people from this village have already experienced this. 

This super-colony species won’t be eradicated by the individual efforts of households trying to control these pests on their own perimeters and gardens. Too many satellite nests will survive, and the population will rebuild. A comprehensive approach is needed that includes gel baits, residual insecticide sprays and granular applications.

  • Gel baits should be applied along ant trails to reach the queens and the larvae in the nests through trophallaxis. This is the key to control, as some queens would otherwise survive, and the infestation could return.
  • A residual insecticide should be sprayed on tree trunks to prevent the ants from feeding on the aphids and to protect homes from ant invasion.
  • A dissolvable granule should be used to treat satellite nests where they can be identified. While granules alone won’t solve the problem, they can help reduce the numbers of hungry insects by tens of thousands.

To get a handle on this serious problem — and perhaps to even solve it completely — all households should report T. magnum sightings to map the infestation. After a thorough inventory, suitable control measures should be planned by professional pest controllers using contact and feeding insecticides, as well as presented to citizens at an informational event. A project of this magnitude could take as long as a year to coordinate.

For more information on tackling ant infestations, contact your country business manager.

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