Health condition of Tilia cordata Mill. trees growing in the urban environment

The aim of this study is to estimate the health condition of Tilia cordata trees in the green areas of Vilnius city (Lithuania) according to damage caused by fungal diseases, crown defoliation, and foliage discoloration. The damage caused to trees by fungal disease agents (Apiognomonia errabunda, Diaporthe eres, Flammulina velutipes, Leptoxyphium fumago, Mycosphaerella millegrana, Nectria cinnabarina, Pholiota aurivella, Polyporus septosporus, Schizophyllum commune, and Tyrostroma compactum) was assessed in street and recreational plantings in 2005-2010. Studies indicated that the intensity of diseases depends on meteorological conditions: during dry and hot summers of 2006, 2008, and 2009, the diseases were less potent (mean grade of damage V varied from 1.3 ± 0.1 to 1.5 ± 0.0), and during wet and warm summers (in 2007 and in 2010) - stronger (V was 2.5 ± 0.1-2.6 ± 0.0). The greatest part (70.7%) of sampled trees was moderately defoliated (crown defoliation 26-60%); slightly defoliated (11-25%) ones constitute 29.3% of assessed trees. Slightly discoloured (foliage discolouration 11-25%) trees comprised 85.7% of the assessed trees, whereas moderately (26-60%) discoloured trees comprised 14.1% of the assessed trees. Crown defoliation and foliage discolouration of trees in recreational areas was lower than in street plantings. The largest crown defoliation and foliage discolouration was assessed with regard to the street trees, which were damaged by the agent of sooty mould Leptoxyphium fumago (V = 2.9 ± 0.0) and leaf spot agents Mycosphaerella millegrana (V = 2.1 ± 0.0). Moderately defoliated and discoloured trees from recreational areas were strongly damaged by fungal leaf spot disease agents Mycosphaerella millegrana (V = 2.6 ± 0.1) and Apiognomonia errabunda (V = 1.8 ± 0.0). Linear regression analysis showed that crown defoliation and foliage discolouration increases by increasing the grade of fungal damage (R2 = 0.51 and R2 = 0.59, respectively; p < 0.05).