Development of apple scab in the crimea

Abstract

The objective of the research is to study the features of the development and etiology of scab in different climatic zones of the Crimea, to evaluate the resistance of apple cultivars to pathogens of apple scab Venturia inaequalis (Cooke) Winter and to develop regional systems for the protection of apple trees in the context of short-term prognosis of the disease. The research methods are generally accepted in phytopathology and plant protection ones, which serve for identifying and accounting the infectious potential of the scab pathogen; disease monitoring; study of the features of the pathogen’s development. As a result of research the possibility of expression of three epidemiological models of scab development in the Crimea is established. In 2016, there were epiphytotic types of the disease’s development, when the maturation of 75 % ascospores occurred before flowering. 6-8 generations of the ascigerous stage of infection and 15-17 generations of conidial stage were realized during the season. Meteorological conditions in 2017 contributed to the expression of a moderate type of development of the disease. The 2018 year as a whole was dry and differed with an atypical cascade of temperatures and humidity during the spring period. The development of the disease was depressive, in the first half of the growing season - up to 2 %, in the second half - 35 %. The degree of vulnerability to scab of the main cultivars grown in different agro-climatic zones of the peninsula is established. The following cultivars are sensitive to the disease: Idared, Golden Delicious, Renet Simirenko, Krymskoe, Eva, Gala, Kandil. The cultivars Jonagold and Fuji are tolerant to the intensity of the expressions of the scab in the southern regions of the Crimea. The cultivar of the Crimean breeding Florina showed a weak character of the development of the disease and can be recommended as a donor of resistance to scab pathogens. On sensitive cultivars, losses of standard products in the year of epiphytotics (2016) reached an average of 69 - 81 % of the expected yield.