Management of Collar rot disease of Potato caused by Sclerotium rolfsii Sacc. through plaster of paris

Abstract

Sclerotium rolfsii Sacc. is a soil borne fungal pathogen infects more than 500 species of plants in about 100 families. Management of this pathogen is much difficult because of its wide host range and soil borne in nature. An experiment was conducted to manage collar rot in potato using plaster of paris (CaSO4.½ H2O) and microbes. Effect of plaster of paris (@ 2.5g/infected collar region of plant) on two different growth stages (mycelial stage and sclerotial stage) of S. rolfsii isolated from infected potato plant was determined. Plaster of paris was applied directly as powder form over the infected area and adverse effect on the fungus was recorded. The whitish mycelial growth of the fungus from collar region of all the treated plants was found to disappear. Further formation of sclerotia was stopped. The existing sclerotia became deformed and dried. The sclerotia and small bits of treated infected plant tissue when transferred to PDA medium no mycelial growth and sclerotial germination was observed. Whereas, from the untreated infected plants, growth of thick whitish fan-shaped mycelial growth was observed with huge numbers of sclerotia. A field experiment was also conducted using four biological agents (Pseudomonas fluores cens (Flügge) Migula,Trichoderma viride Pers., Azotobacter chroococcum, Glomus fasciculatum (Thaxt.) Gerd. and Trappe emend. C. Walker and Koske), two organic amendments (vermicompost and neem cake enriched with neem oil), and one building material (plaster of paris) for managing the disease at Benuria under Red and Lateritic Agroclimatic Zone of West Bengal during 2014- 15. Randomized Block Design was adopted with three replications. The treatments, vermicompost @ 6kg/ plot i.e. 5.5t/ha, neem cake enriched with neem oil @ 2.2kg/plot i.e. 2t/ha,Pseudomonas fluorescens @ 10g/plant, Trichoderma viride @ 10g/plant, Azotobacter chroococcum @10g/plant, Glomus fasciculatum @10g/plant were applied directly once in the field just before planting. The plaster of paris @ 2.5g/plant was dusted twice at the collar region of plant at fifteen days interval starting from 15 days after planting. Severity of the disease recorded highest in control plots (8.95 and 19.88%) followed byGlomus fasciculatum (4.92 and 8.11%), neem cake (4.55 and 5.51%) and Trichoderma viride (2.50 and 4.74%) treated plots while lowest disease severity recorded in plaster of paris (0.70 and 2.65%) followed by vermicompost (1.05 and 3.80%),Pseudomonas fluorescens (1.41 and 4.30%) and Azotobacter chroococcum (1.38 and 4.20%) treated plots at 60 and 75 days after planting, respectively. The per cent disease control (PDC) at 75 days after planting was highest in plaster of paris (90.24%) followed by vermicompost (85.82%), Azotobacter chroococcum (83.73%) and Pseudomonas fluorescens(83.38%) treated plots. Trichoderma viride (73.96%) revealed better than Neem cake (62.33%) and Glomus fasciculatum (52.21). No phytotoxicity has been developed on host plants for the application of plaster of paris. These effective treatments can be incorporated in Integrated Disease Management Programme for sustainability.