Biological features of flyspeck (Schizothyrium sp.) development in Krasnodar Krai

Abstract

Sooty blotch and fl yspeck (SBFS) is one of the most harmful diseases of fungal origin developing on the surface of apple fruits and endangering industrial plantations in Krasnodar Krai. For a long time, fl yspeck was believed to be caused by Schizothyrium pomi (Mont. & Fr.) Arx.; however, over the past 15 years, 12 pathogens from the Schizothyrium and Zygophiala genera have been identifi ed. Data on the biological characteristics of fl yspeck-causing fungi obtained in the USA, Europe, China, Turkey, and other countries indicate signifi cant diff erences in their development depending on the weather conditions of the year and the climate of the area. In connection with the increasing harmfulness of these pathogens in Russia, we set out to study the bioecological characteristics of pathogens of the Schizothyrium genus developing in fruit agrocenoses. The studies were conducted in 2021–2024 in the Black Sea horticultural zone of Krasnodar Krai. The infection was found to persist in the form of thyriothecia on 16 plant species from 11 families (Cornaceae, Rosaceae, Staphyleaceae, Salicaceae, Sapindaceae, Betulaceae, Ranunculaceae, Fagaceae, Ulmaceae, Smilacaceae, and Caprifoliaceae). Blackberry was identifi ed as the main reservoir plant due to its widespread distribution in the study area. The level of over-wintering infection during the study period varied from 5.3 to 12.3 thyriothecia per cm of blackberry shoot. It was established that from 22.3 to 44 % of the fungus fruiting bodies do not survive the winter period. The development of thyriothecia begins in March–April followed by spreading of ascospores in April–May, up to the second or third ten-day period of June. The fi rst symptoms of apple fruit damage by fl yspeck are noted from the second ten-day period of July to the fi rst ten-day period of August. The prevalence of the disease during the harvest period varied from 1 to 50 % in cultivated areas and from 10.3 to 76.3 % in uncultivated areas. The analysis of weather conditions allowed us to conclude that air humidity, precipitation amount, and hydrothermal coeffi cient (HTC) in the summer months of vegetation determine the harmfulness of Schizothyrium sp