Powdery mildew of oak in protective forest plantations of the Volgograd region

In the conditions of the Volgograd region, the source of infection of oak with powdery mildew (the causative agent is Erysiphe alphitoides (Griffon et Maubl.) U. Braun et S. Takam.) is the conidial and marsupial stages of the fungus - ascospores, which overwinter in fruit bodies (cleistothecium) almost within the entire range of the host. The development of the disease on the leaves of the shoots of the first growth depends on the phenological features of the oak and the weather conditions of the first growing season. When studying the regularities of oak phenology and the manifestations of the disease, systematic observations were carried out during the growing season in stands of pedunculate oak (Quercus robur L.) with a periodicity of 10 days. The phenology of oak was studied on 100 specimens of plants in protective forest stands on the territory adjacent to the city of Volgograd. At the same time, the development of powdery mildew of leaves was recorded, and conidium was captured using slides, with the help of agar-strips applied to them. The intensity of spore formation during the growth of the fungus was determined using the Goryaev counting chamber by the number of spores in a certain volume of suspension. Weather conditions for phenological observations were recorded using meteorological data for the period of studying the dynamics of the summer of powdery mildew-conidia and taken from the site “Pogoda i klimat”. It has been established that the seasonal development of conidia Erysiphe alphitoides is determined by a combination of the thermal regime and the conditions of humidification of the growing season. With the help of regression analysis for oak plantations in the arid zone of the Volgograd region, a prognostic model of a short-term meteorological and biological forecast of powdery mildew was developed, which made it possible to establish the dates of the disease and the terms of plant treatment through the dynamics of the spread of conidia.