Assessment of Losses in Sweet Sorghum Genotype (SSV 74) due to Leaf Blight caused by Exserohilum turcicum (Pass.) Leonard and Suggs

Background: Leaf blight caused by Exserohilum turcicum (E. turcicum) is commonly or generally found on sorghum grown in the sub-tropics and tropical lowlands during summer. The pathogen is easily wind disseminated and apparently most consistent in their occurrence and severity across the diverse sorghum growing environments. The sweet sorghum variety SSV 74 was released by University of Agricultural Sciences, Dharwad for kharif season mainly for fodder purpose. This variety is also good for ethanol production and jaggery making. However, for the last several years this variety was showing its susceptibility to the leaf blight caused by E. turcicum and causes heavy losses both in fodder and its quality. Even though there are reports of the presence of leaf blight caused by E. turcicum on the grain sorghum, no precise information is available on the presence of the leaf blight on sweet sorghum in India as well as in the world and no information is available about the magnitude of losses caused by this disease. Hence, the experiment was conducted to assess the losses caused by the E. turcicum. Methods: An experiment on loss assessment in sweet sorghum due to leaf blight caused by E. turcicum was carried out at Main Agricultural Research Station, University of Agricultural Sciences, Dharwad, during kharif 2017 using randomized complete block design (RCBD) with three replications and seven treatments. Six treatments were imposed with hexaconazole at 0.1% besides a treatment with unsprayed control. Result: Lowest per cent disease index (PDI) (24.76%) as well as area under disease progressive curve (789.61) was observed in treatment involving six sprays of hexaconazole at 0.1% followed by five sprays, (PDI: 27.51%, AUDPC: 815.32) and four sprays T4 (PDI: 32.57%, AUDPC: 908.80). Highest fodder yield (46.47 t/ha), brix value (12.47%), crude fibre content (28.22%), leaf ash content (23.08%) and crude protein content (5.29%) was observed in treatment with six sprays of hexaconazole at 0.1%. With respect to the per cent increase over control, 17.47-37.20 per cent increase in fodder yield, 7.4-21.17 per cent in brix value, 11.64-9.66 per cent in crude fibre content, 12.74-62.91 per cent in leaf ash content and 4.36-13.00 per cent in crude protein content was observed at one spray to six sprays with hexaconazole at 0.1 per cent, respectively.