Impact of air pollution on the occurrence of Rhytisma acerinium "tar-spot" on mapie leaves

The aim of the study was, to find out whether the occurrence of Rhytisma acerinium and the variability of numbers of the "tar-spot" fungus on Acer platanoides leaves depend on the degree of environmental pollution. A significant variability was found between sites in relation to contents of chemical elements in soils, leaves and numbers of "tar-spots". The similarity of sites presented in dendrograms classified them as industrial, urban-agglomeration and vehicle-transport areas. The factor and PCA analyses showed that two factors differentiate the soil of the sites in respect of Fe, Cu, Co, Mo, Cr, Ni, Cd and N, S, Mn, Pb. In case of leaves of A. platanoides populations differentiate them in respect of N, S, Fe, Pb, Zn, Co, Be, Cr, Cd and Mn, Cu, Mo. The different air pollutions affect significantly the numbers of "tar-spots" on leaves. Sites with the highest contents of elements do not show "tar-spots", and the factors restricting their occurrence are the high contents, mainly of N, S (NOX, SOX) and heavy metals. In sites, with the lowest contents of these elements massive infections take place. The occurrence of R. acerinium corresponding with the level of site pollution can be used as a tool for evaluation of the degree of environmental pollution.