Evaluation of the effect of pre-sowing treatment of grain sorghum seeds with fungicides on the development of blotches in the forest-steppe of the Samara Region

Abstract

Relevance. It is important to evaluate the effectiveness of modern fungicides and their effect on the development of leaf infections of grain sorghum in order to optimize plant protection against diseases. Methods. The studies were carried out in the fields of the Volga Scientific Research Institute of Selection and Seed-Growing named after P.N. Konstantinov on grain sorghum variety Premiere in 2014–2016. Leaf diseases were estimated by eye in the field during the phases of flowering, milky, waxy, and full grain ripeness. The average lesion of each plant was evaluated, and the prevalence and intensity of disease development was established. Seeds were treated immediately before sowing. Biological effectiveness of the studied fungicides was determined by prevalence and intensity of disease development. Results. Analysis of leaves showed that quite a wide complex of pathogens belonging to the kingdom of fungi caused blotches on sorghum leaves. Mycelium and spores of fungi Alternaria sp., Fusarium sp., Helminthosporium sp. and others were detected on the affected leaves in the stain area. The obtained results allow us to conclude that the development of the fungal leaf blotches in sorghum in the conditions of forest-steppe of the Samara region considerably depends on hydrothermal conditions of the year: the more arid are conditions of May and June, the higher amount of precipitation and thelower temperature is in July, the higher is leaf blotch infestation of sorghum. Seed pretreatment with fungicides suppressed fungal leaf blotch development in the Premiere variety by 13.6–47.0 % in 2014, 6.9–62.2 % – in 2015, and 3.5–53.7 % – in 2016. At the same time, the highest biological efficacy showed treatment of seeds with fungicides of contact-system action “Fundazol” and “Vitaros”; was 25.0–75.0 % in prevalence and 26.2–62.2 % in the intensity of leaf blotch development.