Attack! It hisses and steams. Richard Blantz from the Karlsruhe Horticultural Department holds a spray lance on the stone wall and rinses the gaps between the stones and the sandy ground on which the wall stands with 110 degree water in the Neureut district. Thousands of ants and their brood soon drift lifelessly in the puddles, a never-ending stream. The introduced ant species Tapinoma magnum, which causes enormous damage and can make houses uninhabitable, is being combated.
Day after day from spring to late autumn or even into the winter, infected streets, squares and parks in Karlsruhe are swept away with hot water vehicles. Blantz calls it a Sisyphean task. “The battle can no longer be won,” says Karen Eßrich, who has been leading the charge on the issue in Karlsruhe since last year. Extinction impossible. All that remains is to prevent the so-called super colonies from spreading further.
The number of affected communities is growing - where Tapinoma occurs
The number of municipalities affected in Baden-Württemberg where the animal has been detected is now almost 90, say the Environment Ministry and ant expert Manfred Verhaagh. According to Verhaagh, the southwest, with its Mediterranean climate that is pleasant for the ants and partly sandy soils in the Rhine plain, has the highest number of communities infested by the animals in the country, according to Verhaagh. And they should take the issue very seriously, he emphasizes.
Eßrich takes the topic very seriously. Karlsruhe-Neureut is home to what is probably Germany's largest Tapinoma colony, a super colony that has made itself comfortable on a whopping 100 hectares. Billions of animals are likely to be swarming around there - most underground, around 20 percent above ground.
Sleep disorders, depression - what the ant does
They are then visible to people and can be felt in an extremely annoying way when they climb up legs and arms when there are so many ants in the house or on the terrace that neither vacuuming them up with a vacuum cleaner nor common ant baits help. “That’s the unpleasant thing: you can’t save yourself from the ants,” says Eßrich.
Residents despair because they cannot control the animals in their garden and in their house. In the Palatinate, a woman sold her home out of desperation and emigrated to Tenerife, as Verhaagh reports. There are also people who no longer go on vacation, who have sleep disorders, who become depressed - "these are side effects of this ant plague," says Andreas Martens. He heads the Institute of Biology at the Karlsruhe University of Education - and has developed a special trap. This is supposed to help fight the animals.
Walkways, walls and terraces - what the ant destroys
Because “affected areas” – that sounds harmless, but it’s not. The community of Kehl made headlines, where Tapinoma hordes invaded distribution boxes, paralyzed the internet and made a playground temporarily unusable. As in Karlsruhe, curbs are lowering and walls are in danger of becoming loose and collapsing due to joints infested with ants.
Fighting the ant - which isn't possible
Municipalities apply different measures. They work with bait, with exterminators, with pest controllers or with vehicles with hot water attachments. Not yet tested, presumably expensive, but theoretically possible: freezing with nitrogen.
Martens' traps are also used in Karlsruhe: perforated stones with a black pond liner over them. Tapinoma magnum loves it dry and soaks in it, he said. When there are ants, brood and as many queens as possible inside, the stone is dumped into a bucket of water. Dishwashing liquid is added so that the ants can no longer climb out. The trap is well suited for private properties - because if homeowners don't go along with it, then it becomes even more difficult. According to Eßrich, other municipalities have already expressed their interest.
Expensive fun for the municipalities - what it costs to combat it
In Kehl, where the ant has been combated since 2023, the depot costs around 50,000 euros annually. Plus the purchase of the hot water device for 60,000 euros, as a city spokeswoman reports. Previously, they relied on external companies, but that proved to be inefficient. In Nürtingen, people have been fighting against the Tapinoma since this year and, according to a city spokeswoman, they have already spent 14,000 euros on it, and a total of 25,000 euros are currently earmarked for it in the budget.
Karlsruhe paid 120,000 euros this year to purchase the vehicle with the hot water attachment. Plus personnel costs. Plus renovation costs for damaged sidewalks, etc. The ant controllers have been on duty around the clock since May, says Eßrich. “And it’s actually not enough back and forth.” The two-man team previously responsible will now be joined by three more, preferably in action from March/April 2027. Cost: around 250,000 euros per team, just for the staff. That would be one million euros per year in the already cash-strapped city's budget. “But we have to do something,” says Eßrich.
