Efficacy of Fungicides and Optimization of Application Timing for the Management of Sclerotinia Rot of Mustard Caused by Sclerotinia sclerotiorum

Abstract

Sclerotinia rot of rapeseed-mustard caused by Sclerotinia sclerotiorum (Lib.) de Bary has gained significant importance in Rajasthan, Punjab, Haryana and other major rapeseed-mustard growing areas of India in recent years. Fungicides are extensively used for the control of this disease since no commercial cultivars have been found resistant to S. sclerotiorum and other management practices have not been found very effective. Therefore, the present investigations were carried out to evaluate the efficacy of fungicides and to optimize application timing for the effective management of Sclerotinia rot of mustard. Among 08 fungicides tested in vitro, Carbendazim 50% WP and Propiconazole 25% EC were found most efficient at completely inhibiting the mycelial growth of S. sclerotiorum at all the concentrations tested. In an in vitro sclerotial (carpogenic) germination test, Carbendazim 50% WP completely inhibited sclerotial germination at 100, 250 and 500 ppm. Under artificial inoculation conditions in the field, Propiconazole 25% EC @0.1% was found most effective in reducing Sclerotinia rot incidence (87.04%) followed by Carbendazim 50% WP (83.33%) and Tebuconazole 25.9% EC (75.93%). Similarly, under natural epiphytotic conditions in field, Propiconazole 25% EC @0.1% was found best in disease incidence reduction (85.34%) with increased yield (40.00%) followed by Carbendazim 50% WP (81.25% & 38.09%) and Tebuconazole 25.9% EC (79.72% & 35.24%) in disease reduction and increased yield respectively. Differential time and frequency of application of Propiconazole @0.1% were tested and found that 02 applications i.e. 1st spray at 4.2 flowering stage i.e. 30% bloom stage (70 DAS) and 2nd spray at 4.3 flowering stage i.e. 50% bloom stage (85 DAS) was equally effective in disease incidence reduction (82.70%) with 03 applications i.e. 1st spray at 4.1 flowering stage i.e. 10-20% bloom stage (55 DAS), 2nd at 4.2 flowering stage (70 DAS) and 3rd at 4.3 flowering stage (85 DAS). Therefore, the optimization of fungicide application timing and the number of sprays with adequate concentrations is advisable to increase the cost-effectiveness of crop production while controlling the disease.