Oak processionary posed a health threat. In April 2018, an outbreak of the caterpillars was reported across Greater London and surrounding areas. The moth is now fairly common in Belgium, notably in the Campine but also elsewhere, with fluctuating population numbers from year to year. In 2007 infestations in the Belgian province of Limburg were so acute that soldiers were deployed to burn them. In the Netherlands, the caterpillars are dealt with by biological pest control. Local authorities use, like in Germany, fluids containing bacteria that are toxic only to the caterpillars. These fluids are sprayed onto the infected trees. Furthermore, an
Lepidoptera migration migratory butterflies and moths that reach north-western European countries like the Netherlands, Belgium and the United Kingdom. Research in the United Kingdom confirms that an increasing number of migrants reach the country. Because one would expect that migratory species can adapt to new circumstances quite well, the researches warn for new species that can have a negative impact on native species and possible damage to both health (species like the oak processionary) and agriculture. Lepidoptera migration Many populations of Lepidoptera (butterflies or moths) migrate, sometimes long distances, to and from areas which are only suitable for part of the year.