Dangerous oak processionary moth is being combated again

The oak processionary moth loves the warmth. Like certain mosquito and tick species, the pest benefits from climate change and is increasingly spreading in Germany. As in Baden-Württemberg, Bavaria, Rhineland-Palatinate, North Rhine-Westphalia, Hesse, Lower Saxony, Saxony-Anhalt, Berlin, Brandenburg and Mecklenburg-Western Pomerania, it has now also established itself in Saxony, according to the Julius Kühn Institute's Forest Protection Institute.

The infestation situation in the federal states varies greatly. The damage caused by the offspring of the butterfly to oak trees in forests and settlements is currently considered to be less acute than the health effects of the stinging hairs on humans and animals.

Health problem for humans

The fine stinging hairs of the oak processionary moth are formed from the third larval stage, break off easily and contain the nettle toxin thaumetopoein. They can be spread over long distances by the wind. With the help of their barbs, the hairs attach themselves to the human skin and cause itching, swelling and occasionally asthma attacks. The thaumetopoein intensifies the symptoms of so-called caterpillar dermatitis. Eye irritation is also possible.

The processionary moth has been increasingly present in Germany since the mid-1990s. In Saxony-Anhalt, among other places, a link to climate change has been established: "This can be explained above all by the fact that the now significantly earlier budding of the oak due to increased temperatures accommodates the development of the oak processionary moth after egg laying," according to the Ministry of Agriculture.

The processionary moth is a moth that flies from late July to early September and prefers to lay its eggs on free-standing oak trees. The brown-yellow or gray-black caterpillars hatch in mid to late April and feed at night. They live in colonies and line up like a procession when moving from one place to another - hence their name. Their nests are round webs that can reach the size of a soccer ball.

Successful control

In many regions, the spread is being combated more intensively in recent weeks. The district of Lüneburg in Lower Saxony, for example, has been successfully using so-called nematodes for three years. These tiny nematodes are sprayed alive onto the treetops and combat the caterpillars, which are up to three centimetres long.

"The nematodes are a natural product that is harmless to humans, not harmful to the environment and effective against 90 percent of the oak processionary moth population," explains Jens-Michael Seegers, Head of Road Construction and Maintenance. As the small nematodes are sensitive to light, spraying takes place after sunset.