Infectious diseases of branches, bark and wood of horse chestnuts (Aesculus L.) in urban plantings of Sochi

   Long-term studies of the vital state of horse chestnuts (Aesculus L.) in urban plantations of Sochi have revealed their not-well condition in Sochi urban plantatings – the prevalence of weakened (74.7 %), severely weakened (11.6 %) and dying trees (5.3 %) in all urban planting types and a relatively small percentage of healthy trees (7 %). The main reason for the deterioration of the vital condition of horse chestnuts were infectious diseases of wood, bark and branches caused by 19 species of phytopathogenic organisms. The pathovar of the phytopathogenic bacterium Pseudomonas syringae pv. aesculi was first discovered in Sochi. It caused bacterial bleeding cancer disease, leading to localized death of the cambium and the formation of perennial bark wounds and cracks, often deep crevices in the trunk. The decisive factor in the gradual weakening and death of adult horse chestnut trees were xylotrophic fungi (16 species) – causative agents of stem, butt and wound rot, among which the most significant in terms of occurrence and harmfulness the causative agents of stem rot – Cerioporus squamosus and Spongipellis spumea – and associated fungal species – Flammulima velutipes and Volvariella bombycina, as well as the causal agents of butt rot – Ganoderma applanatum and G. lucidum – and wound rot – Chondrostereum purpureum, Cerrena uncolor, Schizophyllum commune and Stereum hirsutum – should be recognized. Deterioration of the vital state of horse chestnuts in the row "park plan-tings – intra-block plantings – plantings on the embankment of the river Sochi – street plantings" was mainly due to the increase in the proportion of weakened, severely weakened and dying trees affected by various stem and butt rots and bacterial bleeding cancer disease. The three main types of infection gates for the infecting of horse chestnut wood with xylotrophic fungi were unhealed cuts on the trunk and skeletal branches, deep cracks in the bark and crevices in the trunk (a consequence of damage by bacterial bleeding cancer disease) and deep wounds to the trunk and butt caused by construction equipment and vehicles.

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