Observations of ash tree disease in Sweden were first noticed in 2001. This aggressive fungus, Chalara fraxinea, attacks leaves and young shoots from where the fungi grow to form cancer which kills trees. The TFDIs in 2009 and 2010 showed that seriously defoliated ash trees (indicating diseases presence) were found in all areas where ash occur. A higher frequency of seriously defoliated ash trees in the south-eastern part of the country confirms that the spores are spreading by wind from areas with a highly infection of ash tree disease in Southeast. The frequency of seriously defoliated ash trees did not increase in 2010.
Although tree species such as ash and elm represent less than 1 % of the total standing volume in Sweden they are significant in the landscape of agricultural areas. Both elm and ash have been exposed to diseases and are now declining rapidly. Read more about Ash tree disease.