We continue the conversation about the current problem at the moment - potato rhizoctoniosis.
The source of infection are diseased potato plants and some weeds. The main factors in the transmission of the pathogen from year to year are soil and diseased potato tubers (the frequency of transmission of the pathogen through tubers is from 29 to 70%). The transmission of the pathogen during the season occurs through the soil, as well as by basidiospores at high air humidity (86-96% or more) by airborne droplets, but this mechanism is of additional importance.
Thus, the circulation of the pathogen in nature occurs due to a combination of soil and tuber transmission mechanism from year to year, with an additional airborne transmission during the season. Based on this, in order to protect potato plantings from rhizoctoniosis, it is necessary to use techniques and methods to reduce the initial stock of pathogen infection in the soil and on tubers.
Of great importance in the prevention of plant damage by disease is the correct application and combination of agrotechnical and chemical methods.
In order to prevent the development of the disease on potato plants, as well as the infection of tubers, it is necessary to observe crop rotation and return potatoes to their original place no earlier than after 3-4 years. Growing potatoes in a crop rotation after green manure, soybeans, cereals, perennial grasses reduces the development of rhizoctoniosis on sprouts, stems and tubers by 2,0-2,7 times.
In case of impossibility of conducting crop rotation, it is necessary to use crops with phytosanitary properties against the causative agent of rhizoctoniosis as precursors. To improve the phytopathological situation on potatoes, as phytosanitary crops (predecessors), it is recommended to use cereals, perennial cereal grasses, legume-cereal mixtures, carrots, lupins, soybeans, cabbage crops, and flax, which significantly inhibit the development of R. solani Kühn. in the soil.
The basis for their use is that the infectious onset of pathogens persists for a long time in the soil only in a state of forced dormancy. Root secretions of agricultural crops resistant to the causative agent of potato rhizoctoniosis provoke the germination of pathogen propagules in the soil. In this case, the spores of the phytoparasite and their germinal hyphae, not meeting a susceptible host plant, partially die. Due to the fact that soil pathogens, as a rule, have a weaker competitive ability compared to soil-dwelling saprotrophic microorganisms, this technique leads to a decrease in the density of pathogen populations.
In addition, decaying post-harvest residues of phytosanitary crops contribute to an increase in the number of antagonist saprophytes in the soil, which in turn cause the lysis of infectious structures of pathogens, and also take the place of pathogens in the ecological niche.
It is also known that wheat, barley, oats, rapeseed and mustard are producers of antifungal substances. Thus, plants belonging to the cereal family contain purothionine, phenol-type compounds, benzoxazolinones, hordecin, furfrurol, gramine alkaloid, yellow pigments in their cell sap, and cabbage plants contain allyl mustard, phenylethyl mustard and crotonyl mustard oils, rafanin, heirolin, which inhibit the growth of pathogenic microflora.
In Siberia, during one growing season, such predecessors as rapeseed and sarepta mustard most of all reduce the abundance of R. solani in the soil. By May of the next year, due to the release of substances that inhibit the development of the fungus from decomposed crop residues, the number of propagules of the causative agent of rhizoctoniosis is reduced by 2,0 times. Oats do not have a significant effect on soil cleansing, but it allows to stabilize the number of the pathogen. Wheat and barley not only favor the accumulation of the pathogen during the growing season, but also contribute to its persistence in the soil until the next spring. Thus, from the point of view of phytosanitary, the best precursors for potatoes are spring rapeseed and mustard sarepta. When placing a crop on oats, spring barley and wheat, it is necessary to take into account data on the accumulation of the causative agent of rhizoctoniosis in the soil.
List of sources used:
- Zeiruk V.N. Efficiency of specialized crop rotations and biologized system of potato protection from diseases and pests / V.N. Zeiruk, V.M. Glez, S.V. Vasilyeva, M.K. Derevyagin, V.I. Sedova, N.A. Gaitova, L.V. Dmitrieva // Potato growing in the regions of Russia: Actual problems of science and practice. - M., 2006. - S. 38-47.
- Ivanyuk V.G. Agrotechnical ways to combat potato rhizoctoniosis / V.G. Ivanyuk, O.T. Aleksandrov, V.I. Kalach // Protection and quarantine of plants. - 2001. - No. 11. - S. 18-19.
- Ivanyuk V.G. Features of the manifestation of potato rhizoctoniosis in Belarus / V.G. Ivanyuk, O.T. Aleksandrov // Mycology and Phytopathology. - 2000. - T. 34, no. 5. - S. 51-59.
- Loshakov V.G. Crop rotation is a fundamental link in modern farming systems / Loshakov V.G. // Bulletin of the Russian Academy of Agricultural Sciences. - 2006. - No. 5. - S. 23-26.
- Shaldyaeva E.M. Monitoring of rhizoctoniosis in potato agroecosystems in Western Siberia / E.M. Shaldyaeva, Yu.V. Pilipova, N.M. Konyaev. - Novosibirsk, 2006. - 196 p.
- Shaldyaeva E.M. Optimization of the phytosanitary state of potato plantations using spring rapeseed as a green manure crop / E.M. Shaldyaeva, Yu.V. Pilipova, M.P. Shatunova // Plant Protection in Siberia: Sat. scientific tr. teachers and graduate students of the Faculty of Plant Protection. - Novosibirsk, 2003. - S. 77-83
- Carling DE Effect of temperature of virulence of Rhizoctonia solani and other Rhizoctonia on potato / DE Carling, RH Leiner // Phytopathology. - 1990. - V. 80, No. 10. - P. 930-934.
