Assessment of plane trees health status in urban green areas of Sofia, Bulgaria

Health status of plane trees (Platanus spp.) was observed in twenty urban green localities on the territory of Sofia city. Field inventories were conducted in June-October 2022. In the studied localities Platanus × acerifolia was the dominant species, comprising 90.5% of all trees, and the rest ones were Platanus orientalis L. According to the age, the largest share (63.2%) was occupied by mature trees at the age >60-100 years. The vitality of trees was assessed by estimating the degree of defoliation, presence of dieback and dry branches in the crowns. The average defoliation varied between 5% and 71.7%, but the majority of trees were in defoliation range between 30% and 50%. In good health conditions (0-25% defoliation) were the trees in five localities (City Garden, Slaveykov Square, National Palace of Culture, Vazrazhdane Park, Earth and People National Museum Park), where no drying in the top of the crowns was observed. The results reported in this study show that damages caused by biotic agents were associated with relatively different impact of identified pests and diseases. The relatively greater negative effect on the health status of trees was determined in attacks caused by the sycamore lace bug (Corythucha ciliata) and anthracnose disease (caused by the fungal pathogen Apiognomonia veneta). In two localities the fungal pathogens Armillaria mellea and Cytospora platani caused severe damages on studied trees. The decorative qualities and tree vitality of solitary plane trees in Sofia are threatened by negative impact of the biotic factors.