Oak processionary moth spreads across Denmark, researcher says

The oak processionary moth, known in Danish as helvedeslarven (“the larva from hell”), is now established in Denmark, according to insect researcher Thomas Pape of the Natural History Museum of Denmark.

After initial outbreaks on Funen, the allergenic caterpillars have been found in Copenhagen’s Amager district and on the island of Mors. On Mors, the larvae were discovered on an oak tree purchased from a Funen nursery; the tree was subsequently burned and removed.

Pape told Danish broadcaster DR that the species appears to be spreading both east and west, and Danes may need to accept it as part of the country’s fauna. He stressed, however, that widespread tree felling is not the solution, though local removals may be necessary in heavily affected urban areas like Odense, where 850 nests were treated with hot foam in February 2025.

He urged affected municipalities to map the scale of infestations and warned the public against handling the caterpillars themselves. The larvae, which cause severe allergic reactions, will mature into moths in about two weeks.

The moth spreads in two ways: long-distance via infected nursery trees, and locally through adult females laying eggs within 100–500 meters. Pape advised homeowners with oak trees to inspect trunks and thick branches carefully and report any sightings to local authorities.