Oak processionary moth detected in Sweden after crossing from Denmark

The oak processionary moth, a species that has caused significant disruption in Denmark, has now made its way to Sweden. Zooecologist Lars Pettersson from Lund University confirmed the first sighting in 12 years, identifying the specimen as a male.

"A wise thing is to, just to be safe, not pet any hairy caterpillars at all," Pettersson advised. He explained that while male moths can fly considerable distances, the absence of females means there is no immediate risk of the species establishing a breeding population in Sweden. Previous sightings in Sweden, dating back to 2004 and 12 years ago, also involved only male moths.

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A wise thing is to, just to be safe, not pet any hairy caterpillars at all.

The moth's larvae are the primary concern. Their hairs contain a substance called thaumetopoein, which can cause painful rashes and respiratory issues upon contact with human skin or inhalation. This has led to school closures and sanitation efforts in Denmark.

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If a female appears, they lay eggs on an oak. They then become larvae, but that would be next spring. The developed moths are not dangerous, but the larvae are.

Nils Carlsson, head of the nature unit at the County Administrative Board of Skåne, had previously warned that the oak processionary moth could establish itself in Sweden. He noted that as the climate warms, many species naturally shift northward, and this species is not considered invasive by definition. However, Carlsson expressed concern about Sweden's preparedness, pointing out that while there's no specific legislation, the problems seen in Denmark highlight the need for a response.

The oak processionary moth gets its name from the larvae's habit of gathering in groups on oak trees and moving in a procession-like manner when seeking new feeding sites. The related pine processionary moth has been present in southern Gotland for a long time.

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In such cases, there is no legislation and no mandate for county administrative boards or the Swedish Board of Agriculture. What still happens, as is clearly seen in Denmark, is that it suddenly becomes a big problem with demands that someone must deal with it.