The diploma thesis focuses on the indications of the fungus Rhytisma acerinum colonizing the maples Acer spp. in the south-western part of Central Slovakia. During 2017 we evaluated 599 trees in nine locations (Žiar nad Hronom city center, a park in Žiar nad Hronom, a part of a forest above the R1, a part of a forest Istebná, a part of a forest Husárová, Arboretum Borová hora in Zvolen, Arboretum Kysihýbeľ in Banská Štiavnica, a part of a forest Dolné mravenisko, a part of a forest Horné mravenisko). The first results showed the most colonized taxa of Acer spp. by Rhytisma acerinum - A. campestre, A. campestre 'Postelense', A. pensylvaticum, A. platanoides 'Cucullatum' and A. platanoides 'Globosum'. Taxa of maples at least colonized by tar spot are A. japonicum, A. saccharinum, and A. japonicum and almost A. japonicum 'Aconitifolium'. There is non-linear relationship in the evaluation of the correlation between the percentage of coverage of the tar spot and diameter at breast height of the tree. Among the individuals of maple growing in groupand and individuals of maple growing as solitairs, is not shown to be a statistical difference, on the basis of percentage coverage of the tar spot. Different types of management have a significant impact on maple colonization by the fungus Rhytisma acerinum. The highest percentage of coverage of the tar spot is in the forest areas – a part of the a forest above the R1, a part of the a forest Istebná, a part of a forest Husárová, a part of a forest Dolné mravenisko and a part of a forest Horné mravenisko. The lowest values of the percentage of coverage by the tar spot were measured in Žiar nad Hronom city center and in a park in Žiar nad Hronom. Cool climate, high humidity and elimination of pollutants favorably affect a colonization maples by the fungus Rhytisma acerinum. The more favorable climatic condition resulted in a higher percentage of coverage of the tar spot in five locations in Žiar nad Hronom in 2015.