Be careful with infested oaks: The stinging hairs of the caterpillars of the oak processionary moth can cause allergic reactions. In the course of climate change, the problem is likely to intensify.
Measures to combat the oak processionary moth are already underway in many regions of Germany and are being prepared in others.
“We expect from last year’s results that there will be a lot going on in Middle Franconia again,” said Gabriela Lobinger from the Bavarian State Institute for Forestry and Forestry in Freising. After the dry and warm winter, an increase in the population is expected, it was also said from Saxony.
The spread to previously unaffected areas is also to be expected, said Renke Coordes from Sachsenforst. According to the Nature Conservation Union (Nabu), the species is generally spreading more and more in Germany due to climate change.
The animals are not fought less because of the damage to infested trees, but mainly because of the health risks for humans: the caterpillars of the moth have stinging hairs that can lead to painful rashes, eye irritation and breathing difficulties, but also dizziness, drowsiness and allergic shock.
You should therefore not touch the caterpillars – however, you can also come into contact with stinging hairs through drifts. If contact with the hairs cannot be ruled out, it is advisable to change clothes and take a shower.
There are several ways to get rid of the caterpillars. The nests are often vacuumed off. In northern Saxony-Anhalt, aerial control of moth caterpillars recently began. Helicopters spray a preparation there for several days that causes the animals to stop eating. They will then be received within a few days.
The first measures against the caterpillars are also under way in Lower Saxony. In recent years, a spread to the north and in the middle of the state has been observed, said Thomas Brand from the Chamber of Agriculture in Oldenburg. In the district of Lüneburg, the road construction company wants to use a biological agent based on nematodes for the first time. The nematodes are to be sprayed onto the oak trees with a blower after sunset. “The nematodes develop in the body of the caterpillars and thereby kill them,” the circle said.
Fewer oaks a solution
Also with the spraying of a biological agent – it contains a bacterium – the street trees on federal and state roads in Brandenburg are to be protected from the caterpillars. In Weiden in the Upper Palatinate, the animals are collected and the nests destroyed with hot water and foam, as a city spokeswoman explained. In the medium term there will probably be another solution: the planting of oak trees in public spaces will decrease.
Since the oak processionary moth prefers to colonize solitary and well-sunned oaks, it is often found on city and park trees, street avenues, in gardens and parks as well as on the edges of forests – i.e. where people are often out and about.
For Berlin, for example, statistics from the Plant Protection Office show that the number of reports from owners, companies and districts on locations with infested oak trees in the city area has increased significantly since 2013. This year, too, the first reports of nests have already been received.
The oak processionary moth (Thaumetopoea processionea) is a grey-brown moth whose conspicuously hairy caterpillars feed on the leaves and buds of various oak species. The large nests of the animals that hatch in spring can often be clearly seen in infested trees. However, there is a risk of confusion: Bushes and trees that are completely spun in are mostly due to harmless spider moths.
Keep away from infested oak trees
In recent decades, T. processionea has repeatedly multiplied in individual regions of Germany. This can be problematic because the stinging hairs contain the nettle toxin thaumetopoein, which can cause inflammatory reactions in humans and animals, but also symptoms such as drowsiness. You should therefore keep away from infested oaks and never remove nests yourself.
Processionary moths owe their name to the caterpillars’ habit of walking in long rows in procession along trunks and branches in search of food. For the future, things are looking rosy for the species – not only because of the rather mild winters as a result of climate change. As a result of the forest conversion, the proportion of oaks will increase in the future, said Renke Coordes from Sachsenforst.