Tapinoma ant infestation expands across Zurich canton

The invasive Tapinoma ant has spread across about 400,000 square metres between Volketswil and Schwerzenbach in the Zurich Oberland, SRF reports. The two municipalities plan a coordinated eradication campaign from spring 2027.

The infested area is equivalent to around 56 football pitches and is the largest known Tapinoma outbreak in the canton. More than a dozen affected areas have now been identified across Zurich, including Kloten. Several infestations have been eradicated in recent months, but the ant continues to spread, according to the cantonal building department.

How to identify the ant

Tapinoma ants originally come from the Mediterranean region and have spread north of the Alps in recent years. They are now found in several Swiss cantons.

The ants are black and measure between two and five millimetres. They often appear in large numbers and move along conspicuous trails. Ants from the same colony can vary in size.

They are mainly introduced to Switzerland through potted and garden plants. The ants live in soil and can be transported unnoticed, with trade in Mediterranean plants such as olive trees and palms helping their spread. The canton of Zurich is raising awareness of the problem among garden centres and other businesses.

Why the species is a problem

Tapinoma ants form supercolonies containing millions of insects and hundreds of queens. This allows them to spread rapidly and makes them difficult to control.

The ants are not dangerous to people, but they can disrupt everyday life in infested areas. Large numbers can cover gardens, patios and playgrounds. Residents report that the aggressive ants bite, and that some children can no longer play in sandpits.

The ants can also damage facades, insulation and electrical systems, as well as undermine paths, playgrounds and other infrastructure. Cases in Germany have included damaged cables and tunnelled playgrounds.

Early detection improves the chances of eradication

The species can be eradicated, and several infestations in Zurich have already been successfully eliminated. However, large colonies are difficult to treat because all nests and as many queens as possible must be reached.

Volketswil and Schwerzenbach therefore intend to use a joint strategy rather than rely on individual measures by property owners. The municipalities said the precise treatment method has not yet been decided. Authorities first want to locate all entry and exit points before eliminating the nests and queens.

Finding one or two ants in a kitchen or garden does not necessarily indicate an infestation. People should become more alert when very large numbers appear. Anyone who suspects an infestation should contact their municipality or the responsible authorities. Control measures are generally coordinated and carried out by specialists.