Phytopathological Monitoring and Protection of Soybeans From Major Diseases

This article presents the results of a study on the effect of fungicide application on the development of the major soybean pathogens during the early stages of crop development and throughout the growing season, as well as on the indicators used to evaluate the efficiency of soybean production. As a result of the phytopathological monitoring conducted in the soybean agrocenosis, the species composition of soybean pathogens was determined. The phytopathogenic complex was dominated by Alternaria blight and Septoria leaf spot, accounting for 27,8% and 21,5% of the total disease incidence, respectively. A somewhat lower prevalence was recorded for Fusarium root rot (16,3%) and downy mildew (14,6%). Ascochyta blight (10,4%), Cercospora leaf spot (3,2%), white mold (2,6%), and gray mold (2,0%) occurred considerably less frequently in soybean crops. Bacterial diseases accounted for 1.4% of the total disease complex, whereas viral infections represented only 0,2%. It was established that the highest level of biological efficacy in the soybean protection system was achieved through the integrated application of pre-sowing seed treatment with fungicidal seed dressers followed by the application of the fungicide Abacus during the crop growing season. The maximum efficacy against Fusarium root rot (97%) was achieved by combining the fungicidal seed treatment Vibrance at a rate of 1,0 l/t with the fungicide Abacus at a rate of 2,0 l/ha. At the same time, the highest technical efficacy in controlling Alternaria blight and Septoria leaf spot (97–98%) was recorded when the seed dresser Standak Top was applied at a rate of 2,0 l/t in combination with the fungicide Abacus at a rate of 2,0 l/ha. The analysis of yield performance demonstrated that the application of the evaluated fungicide systems significantly increased soybean productivity compared with the untreated control. Seed yield in the experimental treatments ranged from 2,72 to 3,02 t/ha, whereas in the control it did not exceed 2,37 t/ha. The highest seed yield (3,02 t/ha) was obtained following the integrated application of the fungicidal seed treatment Standak Top at a rate of 2,0 l/t before sowing, followed by the foliar application of the fungicide Abacus at 2,0 l/ha during the growing season. Under this treatment, the yield increase reached 0,65 t/ha, or 27,4% compared with the control. The obtained results indicate that the combination of pre-sowing seed treatment and fungicide application during the growing season effectively suppresses the development of the disease complex, improves the phytosanitary status of soybean crops, and creates favorable conditions for a more complete realization of the crop's yield potential within modern soybean production technology.