Poisonous caterpillars of the oak processionary moth spread
The spread of oak procession moths in Germany has expanded significantly in recent years. This is associated with a considerable health risk due to the poisonous caterpillars. The dry and warm spring weather offers ideal conditions for the multiplication of oak processionary moths. Recreation and settlement areas of human beings are also increasingly affected, reports the Julius Kühn Institute (JKI) and warns of the health risks that the larvae of the oak processionary moth can pose.
Oak procession moth plant and health pest According to the Julius Kühn Institute, the mild dry spring offers excellent propagation conditions for the oak procession moths, so that again this year a particularly large number of caterpillars can be expected. According to the JKI, this has negative effects for both flora and humans. On the one hand, the caterpillars of the oak procession moths are plant pests that can eat whole areas of the tree bare and, on the other hand, humans face considerable health consequences if they come into contact with the caterpillars' hairs - the oak procession moths are also considered a health pest. The increasing spread of animals is therefore viewed with concern by the health authorities. The oak procession moths are now widespread in a total of ten federal states, with Baden-Württemberg, Berlin, Brandenburg, Saxony-Anhalt, North Rhine-Westphalia and Bavaria being the most affected, reports the JKI.
Stinging hairs of the caterpillars cause allergic reactions The fine stinging hairs of the oak processionary moth larvae can cause severe allergic reactions if they come into contact with the skin or when inhaled and pose a considerable health risk. The human-pathogenic potential of oak procession moths is based on the so-called stinging hair, "which are formed from the third larval stage", reports da JKI. Until the caterpillars reach the sixth and last larval stage, "the number and length of stinging hair increases with each moult," the JKI continues. The stinging hair is a danger to human health due to the nettle poison it contains. According to JKI, the "caterpillars of the inconspicuous gray butterfly" hatch in late April and early May and pass through six larval stages until pupation around June. During this time, the oak procession spinners pose a significant health risk. In the affected areas, “health effects among forest visitors must be feared,” according to the latest JKI communication.
Difficulty breathing, eye irritation, skin irritation and pseudo-allergic reactions. However, the danger from the caterpillars' hair remains even after the oak processionary moth has hatched. The stinging hairs are present in high concentration in the old webs of the larvae and are preserved there for a long time, so that the old caterpillar nests represent a permanent source of danger. "The contact risk remains in the infested areas for years," said the JKI. The stinging hairs actually serve the caterpillars to protect them from natural enemies. But they can also cause severe health problems in humans, such as breathing difficulties, eye irritation, skin irritation and pseudo-allergic reactions. In addition to the health risks and the “drastic restrictions on the use of affected areas, the heat-loving butterfly species specializing in oak also poses massive problems for forestry,” reports the JKI, which, as the Federal Research Institute for Cultivated Plants in Germany, is also committed to monitoring plant and health pests. The caterpillars are often responsible for the so-called nettle fever.
Climate change favors the spread of oak procession moths According to the experts, climate change makes a significant contribution to the growing spread of oak procession moths. The dry, warm weather in spring creates ideal conditions for the spread of the health-endangering animals. For example, the oak procession moths have been able to reproduce considerably across Germany in recent years and have continued to advance northwards. Most recently the oak procession moths also reached in Lower Saxony and Mecklenburg-Western Pomerania. The experts are therefore looking for strategies that enable effective control of the oak procession moth without harming the health of the population or the plants. At the beginning of March, representatives of the responsible institutions (for example JKI, Federal Ministry of Agriculture, Federal Institute for Risk Assessment, Federal Environment Agency, representatives of forest research institutes, official plant protection services and health authorities) met in Berlin for a technical discussion on the topic "Processionary: facts, consequences, strategies" advise there on possible approaches to combat the oak processionary moth.
Avoid contact with the caterpillars and webs In order to avoid health risks from the burning hair of the oak processionary moth, contact with the animals and especially with the nests should be avoided. However, the fine hairs can also be transported by air, so that the proximity to a nest may be sufficient to cause health problems. At the latest after the larvae hatch, the webs should be removed by a specialist in order to avoid long-term health risks. (fp)
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Image: Caterpillar dermatitis (lepidopterism) due to oak procession spinner (Thaumetopoea processionea) Photo: Daniel Ullrich.