Copenhagen is preparing to combat the oak processionary moth, known as “the caterpillar from hell,” before it reaches the Danish capital. The city plans to invest in preventive measures after neighboring cities like Odense spent millions fighting infestations of the toxic caterpillar last year.
A Dangerous Pest Spreading North
The oak processionary moth, scientifically named Thaumetopoea Processionea, has many names. Danes call it egeprocessionsspinderen. But perhaps the most fitting nickname is “the caterpillar from hell.” This small insect is causing serious concern among officials at Copenhagen’s City Hall, even though it hasn’t arrived yet.
The moth originally comes from Central and Southern Europe but has gradually moved toward cooler climates. In its larval stage, it becomes a troublesome pest. The larvae have tiny irritating hairs that are released during certain growth phases. Contact with these hairs, either through touch or when they’re spread by wind, can trigger allergic reactions.
Hans Peter Ravn, professor emeritus at the University of Copenhagen, explains that not everyone can tolerate exposure to these hairs. The symptoms need to be taken seriously. Some people experience severe itching, rashes, burning sensations similar to stinging nettles, eye irritation, and even breathing difficulties.
Learning from Odense’s Expensive Battle
Last year, Odense discovered several trees infested with the oak processionary moth and launched a major operation to eliminate it. The city spent close to 2.5 million Danish kroner on the effort. Shortly after, larvae nests appeared on trees in Nyborg, Kerteminde, and Horsens.
Anja Hartvig Spork, vegetation manager at Copenhagen Municipality, says officials expect the pest to reach Copenhagen eventually. It’s just a matter of time. The strategy now focuses on showing foresight before suddenly facing the same situation as Odense.
If an outbreak takes hold in Copenhagen, the cost could range between 5 and 10 million kroner. However, if the infestation spreads significantly, the price tag could climb even higher. Getting ahead of the problem is essential.
How the Caterpillar Travels
Evidence suggests the larvae arrived in Denmark through plants imported from Germany. The oak processionary moth isn’t classified as a pest species, which complicates detection efforts. In its earliest stages as eggs, typically between September and April, it’s nearly impossible to spot.
Once the moths emerge, there are virtually no limits to how far they can spread. Female moths don’t fly much, but males are extremely active. With help from the wind, they can travel remarkably long distances. There are documented cases of moths being blown from Germany to Lolland. If they land on a vehicle, they can travel even farther.
Interestingly, the caterpillars don’t cause much damage to oak trees themselves. They eat the leaves, but the trees can withstand this. Instead, humans and animals face the real danger from exposure to the larvae’s irritating hairs.
Characteristics and Safety Measures
The larvae have long white hairs, dark heads, and move in long lines called processions along the trunks and branches of oak trees. Each larva has up to 62,000 microscopic barbed hairs measuring just 0.1 to 0.2 millimeters. These hairs are released upon contact or carried by wind.
The risk period runs from April to July during the larval stage. However, empty nests can remain dangerous for several years. Safety precautions are straightforward: never touch larvae or nests, maintain a distance of 10 to 15 meters, and if contact occurs, rinse with water, use tape to remove hairs, and wash clothing immediately.
People often confuse the oak processionary moth with completely harmless larvae like the ermine moth or woolly bear caterpillar. The key difference is that the oak processionary moth lives exclusively on oak trees.
London Lost Control
London has battled the oak processionary moth for many years. Authorities only take action when larvae appear in places like daycare centers. Otherwise, they leave the trees and larvae alone. The explanation is stark: London has lost control and can only repair damage rather than prevent it.
In the rest of England, prevention efforts are in full swing. Copenhagen wants to follow that preventive approach. The city received an early warning from Odense, making it foolish to sit and wait for an attack. It’s better to respond before the problem spreads out of control.
Copenhagen’s Prevention Plan
According to a report from Copenhagen’s Climate, Environment, and Technology Administration, the preventive work will cost approximately 650,000 kroner initially. After that, ongoing expenses for monitoring and maintaining traps will run around 150,000 kroner annually. This represents a completely different price tag compared to battling a full-blown infestation.
Members of the Climate, Environment, and Technology Committee will ultimately decide whether and when to allocate funds for prevention. Social Democrat member Niels Bjerrum believes there’s every good reason to keep watch and stay one step ahead before the situation develops into a real problem.
Hans Peter Ravn suggests the best approach involves monitoring newly planted trees. This makes it easier to quickly spot any larvae on the trees, and the problem will be simpler to control because the trees are still small. The challenge becomes much greater once trees grow large and strong.
Monitoring All Oak Trees
Copenhagen’s Climate, Technology, and Environment Administration already monitors new trees and can fell them if larvae are found. But more work is needed. Officials must monitor all oak trees in the city, including those in green spaces where registration systems aren’t as comprehensive as in urban areas.
Anja Hartvig Spork acknowledges there’s considerable work ahead. That work apparently needs to begin sooner rather than later. The city aims to avoid the fate of London, where authorities lost track of the problem and now can only respond reactively to the most serious cases.
Sources and References
The Danish Dream: Toxic Caterpillar in Denmark Discovered at Horsens Daycare Center
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