Studies on Management of Sclerotinia Stem Rot (Sclerotinia Sclerotiorum Lib. De Bary) of Lentil

Abstract

Lentil (Lens culinaris Medik.) is an important pulse crop. During the survey for lentil diseases at farmers’ field, the crop was found moderately to severely infected with sclerotinia stem rot caused by Sclerotinia sclerotiorum (Lib.) de Bary. The disease appears as the dark brown spots on the stems, or branches and in later stage plant parts covered with white fluffy mycelium, affected plants appear wilted with yellow specks and ripens prematurely look straw coloured. The fungus produces black seed-like sclerotia, attached to the mycelium, on diseased tissues. Sclerotia on germination produce abundant apothecia. Higher sclerotial germination percentage was recorded when buried at shallower depth and decreased significantly with increasing the burial depth. Carpogenic germination in Sclerotinia sclerotiorum occurred generally more profusely on light soils which were rich in sand, while minimum sclerotial germination, apothecia formation and stipes per sclerotia were recorded in clay soils. Apothecial production was lowest in the soil having high organic matter (9% O.M.) content in soil, whereas the highest sclerotial germination was in low O.M. containing soils. When plant debris were added in sterilized soil there was highest sclerotial germination, apothecia and stipes production per sclerotia. The lowest disease incidence and highest grain yield was recorded in 15th October sown crop during 2015-16 and 2016-17, while maximum disease incidence and lowest grain yield was recorded in 15th November sown crop during both years. There was negative correlation between yield and PDI during both years 2015-16 and 2016-17 and also a negative correlation between avg temperature and PDI at 60 DAS and 90 DAS and a significant positive correlation between relative humidity and percent disease incidence at 60 DAS and 90 DAS during 2015-16 and 2016-17. Antagonist Pseudomonas fluorescence inhibited the mycelial growth of Sclerotinia sclerotiorum followed by Trichoderma viride, while least mycelial growth inhibition was recorded with Chaetomium globosum. The fungicides Propiconazole, Azoxystrobin, Tabuconazole, Hexaconazole and Carbendazim inhibited the mycelial growth of pathogen completely at 100 ppm concentration. The fungicides Thiophanate methyl and Iprodione had intermediate inhibitory effect on mycelial growth inhibition of S. sclerotiorum. While no mycelial growth inhibition was reported with Mancozeb at all the three concentrations tested, followed by Captan. All the systemic and non systemic fungicides significantly inhibited the mycelial growth of Trichoderma viride, the fungicides Propiconazole, Tebuconazole, Azoxystrobin, Hexaconazole, Carbendazim, Thiophanate methyl and Iprodione were incompatible with the T. viride. Two fungicides Captan and Mancozeb were compatible with the Trichoderma viride at lower concentration. For integrated disease management of Sclerotinia stem rot, minimum PDI and Maximum increase in grain yield of lentil was recorded with foliar spray of Hexaconazole 0.1% followed by treatment ‘FYM @ 2kg/m2 + P. fluorescence @ 0.3 g/m2+ Azoxystrobin Foliar Spray 0.1%’ while the foliar application of Pseudomonas florescence (0.5%) was most inferior among the applied treatments. during 2015-16 and 2016-17