Występowanie i proces rozprzestrzeniania się Chalara fraxinea na jesionie wyniosłym (Fraxinus excelsior L.) na terenie wybranych krajów Europy Północnej

Dieback of common ash is a worrying phenomenon that emerged in the early 1990s. The first symptoms were observed in 1992 in Poland. In 1996 the plague appeared in Lithuania, followed by Germany, Denmark, Czech Republic, Austria, Slovenia, Sweden and France (2002−2009), to finally reach the British Isles in 2012. At the beginning it was said about the disease of ash, but a few years later it became the issue of ash dieback. Despite many research and the cause identification, the problem still exists. The aim of article is to show the overall picture and the prior knowledge of the phenomenon on the example of four Northern European countries: Great Britain, Ireland, Denmark and Sweden. Considerations were mainly focused on the UK and Ireland, which because of the insular location are an area of slower spread of the Chalara fraxinea – fungus considered to be the one of the main factors responsible for ash disease. Moreover, the selection is determined by the weather and habitat conditions where the described species have their optimum range. To the contrast, Denmark and Sweden were mentioned also. The described species has a much worse state of health in that countries. In order to describe the current state of the spread of ash dieback, we selected official documents and factsheets available on the government websites. In case of described countries, quick response and proper identification of the cause of ash dieback allowed to take appropriate steps to fight Chalara fraxinea before the disease has spread in the local population. Appropriate government regulation, cooperation with local forest owners, education and action plans at the moment seems to function properly especially in Great Britain and Ireland. Quite other conditions are in the countries of the continental Europe, including Poland, Lithuania, Denmark and Sweden, where the fungus had made quite large losses in stands of common ash long before it was determined the main cause of this phenomenon. Undoubtedly a huge role in the rapid spread of the pathogen has a geographical location and quick response on the disease.