According to the results of phytosanitary monitoring in the Arboretum of the NBG, 26 pest species were identified on 97 tree introduced species (1039 foci). In the Arboretum of the NBG in 2020, 27 species of phytopathogenic fungi (186 foci) were identified on 65 species of woody plants. Of these, 18 species are wood-destroying fungi that cause root and trunk rot in 57 species of tree introduced species (159 foci). In the Arboretum, 5 types of powdery mildew fungi (9 foci) and 4 types of fungi that cause rust (18 foci) were identified. The results of phytosanitary monitoring for the period 2015-2020 were summed up. The number of pest species increased by 8 species and amounted to 26 species of phytophagans, the number of pest foci increased by 32%. The number of foci of phytopathogenic bracket fungi that cause root and trunk rot increased from 103 to 159 units, the increase in foci of pathogens was 56 units. Currently, the number of bracket fungi that cause root rot is 7 species (135 foci), bracket fungi that cause trunk rot - 11 species (24 foci). The number of powdery mildew and rust fungi did not change during the studies. The biology and ecology of cottony-cushion scale ( Icerya purchasi ) was studied.