Phytosanitary condition of age-old trees of the V.V. Pashkevych arboretum of the National Dendrological Park “Sofiyivka” of the National Academy of Sciences of Ukraine

The results of research into the phytosanitary condition of age-old trees in the historical part of the V.V. Pashkevych arboretum are presented. The small triangular-shaped arboretum occupies an area of 1.87 ha, which was founded in 1889–1891 by professor V.V. Pashkevych. As a result of the inventory assessment of the territory (as of 2024), it was established that the taxonomic composition of the arboretum is represented by 90 species and forms of tree species, including 44 from the period of the creation of the arboretum itself. A total of 102 taxa aged 100–135 years were identified. It was determined that representatives of dendroflora belong to 12 families, including 14 taxa from the Pinophyta division and 90 taxa from the Magnoliophyta division. In terms of quantity, the largest number of age-old trees in the arboretum plantings are from the families Malvaceae Juss. (30.75%), Sapindaceae Juss. (13.46%), Fagaceae Dumort. (11.5%), and Pinaceae L. (10.57%), and the smallest number of age-old trees are from Simaroubaceae DC., Ulmaceae Mirb., and Cannabaceae Mart. (0.96%). Rapid climate change significantly reduces the resilience of plantations in the Right-Bank Forest-Steppe of Ukraine and contributes to outbreaks of epiphytoses of bacterioses, the reproduction of pests, and drying out of the surface root system. A set of diseases and pest infestations were found in tree species within the research area, which significantly affected their growth and development and their resistance to current climatic factors. The most common are local necrotic-cancer diseases, caused by the fungi Nectria ditissima; damage by xylotrophic fungi (Poliporus squarnosus and Fomes fomentarius); rot; frost cracks; leaf damage by powdery mildew, the course of which is chronic. A decrease in the esthetic condition of the stand was noted: a sparse and asymmetrical crown, leaves and needles damaged by pests, a trunk tilt from 10° to 40°, a dry tree top, hollowness, etc. According to the sanitary rules in the forests of Ukraine, it was determined that trees of category I of sanitary condition (without signs of weakening) accounted for 31%, trees of category II (weakened) accounted for 36.4%, category III (very weakened) accounted for 25.9%, and category IV (dying) accounted for 6.7%. It was noted that one of the reasons for deterioration in the condition of trees in the stands is colonization by the semi-parasite Viscum album L. As a result of the research, 22 trees with varying degrees of Viscum album damage were identified. Of these, 4.9% were slightly damaged, 6.9% were moderately damaged, 5.9% were severely damaged, and 3.9% were very severely damaged. It was determined that 32 trees required sanitary pruning, 25 trees required pest and disease treatment, and one 130-year-old Robinia psevdoacacia L. tree was recommended for removal.