Rhizoctonia potato disease in production conditions in the forest-steppe of Western Siberia

Abstract

The authors carried out a scientific study from 1990 to 2022 on 20 varieties of potatoes to study the pathogenesis of Rhizoctonia in crop production conditions and substantiate the methods of the system of protection against the disease. The fungus R. Solani persists annually in the soil and on seed tubers in the form of mycelium and sclerotia. It was found that more than 60% of the grounds of potato agroecosystems have the content of the causative agent of Rhizoctonia is many times higher than the established ETH (Economic threshold of harmfulness). Furthermore, monitoring of the phytosanitary state of potato seed material showed that, on average, about 60% of the tubers are inhabited by the causative agent of Rhizoctonia, including about 30% of the sclerotial form, which is six times higher than the phytosanitary regulations. Thus, in the region’s conditions, a double mechanism of phytopathogen transmission is provided annually. The causative agent of Rhizoctonia infects potato sprouts, subsequently causing their complete death (on average 12%) and shootouts, reducing the density of productive plants in crop plantings. At subsequent stages of growth and development of potatoes, significant expansion of the disease on the stems was noted (on average 31.4%), and stolons were damaged and died (9.3 and 5.5%, respectively), which disrupted the processes of stolon and tuberization. In the region’s conditions, Rhizoctonia occurs in the form of epiphytotic with a prevalence of 88% or more. Therefore, the potato protection strategy against Rhizoctonia should be based on methods that reduce the initial population density of the R. Solani fungus in the soils of agroecosystems and on seed tubers. Essential elements of potato cultivation technology are cropping rotation with a saturation of no more than 30% (biological efficiency - 43.2–79.5%); phytosanitary precursor, including green manure pairs (biological efficiency - 49.0–75.9%); mandatory etching with chemical preparations (biological efficiency - 54.9–98.8%) or natural origin. Using entomopathogenic fungi Metarhizium robertsii and Baeuveria bassiana can be a promising direction in reducing Rhizoctonia. Dressing seed tubers with conidia of entomopathogenic fungi suppressed the development of the disease in potato plantings by 1.8–3.7%, providing an increase in yield by 12.1–19.2%. The study of the influence of Metarhizium robertsii and Baeuveria bassiana on the pathogenesis of Rhizoctonia will be continued.