Berlin’s parks, sports grounds, and residential neighborhoods are under siege this summer by a silent but potent threat: the oak processionary moth caterpillar. Since May, the toxic hairs of these invasive pests have forced the closure of public spaces, triggered health warnings, and left residents frustrated by what they call a lack of coordinated action from authorities. The infestation, now spreading rapidly across the city, has turned the German capital into a case study in how climate change and urban ecology can collide with public health—and how bureaucratic fragmentation can exacerbate the crisis.
The caterpillars of Thaumetopoea processionea, as the oak processionary moth is scientifically known, are not merely a nuisance. Their microscopic, venomous hairs—up to 200,000 per caterpillar—can drift on the wind for hundreds of meters, embedding in skin, eyes, and respiratory tracts. Exposure causes severe rashes, conjunctivitis, and asthma-like symptoms; in rare but documented cases, it has provoked anaphylactic shock. Last year alone, Berlin’s Senate Department for the Environment recorded 5,032 infested oak trees across 881 locations, a figure officials warn will surge this year as Germany braces for another scorching, drought-prone summer.
In the Jungfernheide district, where over 11,000 residents live in close proximity to oak-lined streets, the caterpillars have infiltrated every surface. According to B.Z., they have been found clinging to facades, car roofs, door frames, and even streetlights, their nests—web-like structures built high in trees—dropping toxic hairs onto sidewalks below. The district’s housing companies and local politicians have accused the Berlin Senate of moving too slowly. “We’re not just talking about a few trees,” said a spokesperson for the Jungfernheide residents’ association. “This is an invasion that’s making people sick, and the response has been piecemeal at best.” A petition demanding a binding protection plan for the area has already gathered over 4,500 signatures, a rare show of unified frustration in a city often divided by red tape.
The problem extends far beyond Berlin. The oak processionary moth has established itself across Europe, from the Netherlands and France to Denmark and the Mediterranean. In 2006, it accidentally reached the UK, where it is now entrenched in Greater London and parts of southeast England. On Saturday, the British government issued a public warning urging residents to avoid contact with the insects or their nests—a directive echoed in Berlin, where health agencies have struggled to classify the threat. Unlike traditional pests, the caterpillars are regulated as an allergen, not a public-health hazard, limiting the tools available to officials. Meanwhile, strict plant protection laws restrict the use of certain biocides, leaving authorities with few options beyond manual nest removal and public education.
In Berlin, the hardest-hit districts—Charlottenburg-Wilmersdorf, Treptow-Köpenick, Steglitz-Zehlendorf, and Spandau—have seen parks, sports fields, and pedestrian routes temporarily shut down as crews scramble to remove nests. Yet critics argue the damage could have been mitigated with earlier intervention. “We’ve known about this for years,” said a district official in Steglitz-Zehlendorf. “The question is why we’re still reacting instead of preventing.” The answer, residents and experts say, lies in the fragmented governance of Berlin’s 12 districts, where coordination between the Senate, local authorities, and housing companies remains inconsistent.
What happens next depends on whether Berlin’s leaders can break the cycle of reactive measures. The Senate has pledged to accelerate treatment programs, but the clock is ticking. With temperatures set to rise and drought conditions worsening, the caterpillars’ range is likely to expand. In the UK, where the infestation has also surged, local councils have turned to biological controls and community awareness campaigns—approaches Berlin may yet adopt. For now, though, the city’s residents are left waiting, their parks cordoned off, their health at risk, and their patience wearing thin.
The oak processionary moth is not going anywhere. The question is whether Berlin’s institutions can adapt fast enough to stop it from becoming a permanent fixture of urban life.
