The use of biopreparations in the control of soybean endangered by pathogenic soil-borne fungi.
A field experiment was conducted during 2003-04 in a 10-year-old soyabean (cv. Mazovia) monoculture in Czeslawice, Poland, with naturally accumulated infective materials from soilborne fungi. Seeds were treated with Polyversum [Pythium oligandrum], Biosept 33 SL [from grapefruit seed and pulp extracts] and Biochikol 020 PC [chitosan]. These treatments were also sprayed to plants at the beginning of anthesis. Seeds treated with Zaprawa Oxafun T (37.5% carboxin + 37.5% thiram) and plants sprayed with Bravo Plus 500 S.C. (50% chlorothalonil). Untreated seeds were used as controls. The number and vigour of plants were evaluated at the seedling and anthesis stages. The highest number of plants was obtained with Biosept 33 SL, followed by Polyversum or Zaprawa Oxafun T. Biosept 33 SL and Bravo Plus 500 SC were the most effective in protecting the plants from infection by soilborne fungi. Polyversum and Biochikol 020 PC were also effective. The seed yield was highest for Biosept 33 SL and lowest for the control. Soyabean plants were mainly infected by Fusarium spp., Alternaria alternata, Phoma exigua, Rhizoctonia solani and Pythium irregulare. The population of these fungi was greatest in the control plants and lowest in plants treated with Biosept 33 SL or Polyversum. The proportion of pathogenic fungi (Phytophthora sojae, Fusarium spp., Sclerotinia sclerotiorum and Phoma exigua) was lowest in seeds treated with Biosept 33 SL or Zaprawa Oxafun T, and highest in the control.