The spatial distribution of pine mistletoe Viscum album ssp. austriacum (Wiesb.) Volmann in a Scots pine (Pinus sylvestris L.) stand in Central Poland

The evergreen, semi-parasitic pine mistletoe, Viscum album ssp. austriacum (Wiesb.) Volmann, is one of the four subspecies of European mistletoe, Viscum album L. It is frequently encountered on Scots pine communities in Poland. Distribution of pine mistletoe in representative P. sylvestris stand from the central Poland was investigated. The host density and host size to the frequency of Viscum was verified. Within the studied area 46% out of 313 individuals of P. sylvestris trees were infected by mistletoe, among them 78% in low mistletoe infection, 17% in medium and 3% in high infection. Of 1171 infections recorded on pines, 97% were on branches, 4% on the host trunk. The mistletoe individuals had an aggregated pattern of spatial distribution which was mainly explained by the host size. Infected trees are larger than uninfected ones, on average, and within the infected tree population, trees with mistletoe had higher number of dead branches than trees with none infection. Parasitized trees were more prevalent in low-density stands than in high-density stands. Mistletoes occurred mainly on the outer brunches within trees crowns.