Integrated disease management of purple blotch [Alternaria porri (Ellis) Cif] of onion

Purple blotch caused by Alternaria porri is a yield limiting disease of onion commonly prevailing in almost all onion growing areas of the world. The effective management of purple blotch of onion through the application of bio-agent, botanical and fungicides were evaluated under field conditions. Among the eight treatments tested, a positive and significant effect was found with the seed treatment using Pseudomonas fluorescens (5 g/kg) followed by two sprays of difenconazole (0.1%) interspersed with P. fluorescens (0.5%) spray with a per cent disease index of 38.67 and bulb yield of 19.41 t/ha, which was significantly superior over other treatments and control. Whereas, the seed treatment with P. fluorescens followed by two sprays of iprodione + carbendazim (Quintal) (0.2%) interspersed with P. fluorescens (0.5%) spray was on par with standard check (two sprays of difenconazole at 0.1%) with the PDI of 42.00 and 43.33 and bulb yield of 16.64 and 15.68 ton/ha respectively. The control was showing 81.00 PDI with bulb yield of 10.39 t/ha.