Changes in the Distribution of European Mistletoe (Viscum album) in Hungary During the Last Hundred Years

Abstract

The hemiparasitic European mistletoe (Viscum album) from the family Viscaceae (Santalaceae s.l.) is able to infest more than 380 woody taxa in Europe. At the beginning of the 20th century, less than 10 % of Hungary was infested. The distribution area was centralized in the Transdanubian Mountains, and no mass occurrence was noticed elsewhere. Since then, the infested area has almost tripled, and heavily infested forests can be observed in numerous parts of Hungary, especially in the northeast area of the Hungarian Great Plain. However, the central region of the Hungarian Great Plain is still uninfested. In the North Hungarian Mountains, where the presence of potential hosts is very frequent, mistletoe is still quite rare. The most infested macroregion of Hungary is Western Transdanubia, the only region where all three different subspecies can be found. No significant changes have been observed in the proportions of the most common hosts in the last 90 years, with poplars (Populus spp.) and black locust (Robinia pseudoacacia) still being the most frequently infested species. Silver maple (Acer saccharinum) is now a heavily infested host in city parks, while the abundance of infested apple (Malus spp.) and pear (Pyrus spp.) trees has decreased with the transformation of cultivation techniques. In infested areas, nine to twelve of the most common 18 host species can be found, while only five to eight species can be observed in uninfested areas. The increased mistletoe occurrence can be attributed to several factors, including human impact, larger forest area and a growing number of breeding pairs of the mistle thrush (Turdus viscivorus).