Evaluation of Novel Broad-spectrum Fungicides for Management of Rice Blast and Sheath Blight under In-vitro and Field Conditions

Abstract

The present study evaluated the efficacy of eight novel fungicidal treatments against Magnaporthe oryzae (Blast) and Rhizoctonia solani (Sheath blight) under both in-vitro and field conditions. In-vitro efficacy against M. oryzae revealed that, complete pathogen growth inhibition (100%) was exhibited by treatments T2 (Picoxystrobin 7% + Propiconazole 12% EC @ 2.0 ml/L), T3 (Pyraclostrobin 100 g/L @ 2.0 ml/L), T4 (Fluxapyroxad 62.5 g/L + Epoxiconazole 62.5 g/L EC @ 1.5 ml/L), T6 (Propiconazole 20% EC @ 1.0 ml/L) and T7 (Isoprothiolane 40% EC @ 1.5 ml/L) at recommended doses. Whereas, at half-recommended doses, T2 and T3 still maintained high efficacy with inhibition rate of 91.8% and 90.7%. Similarly, for R. solani, treatments T2, T3, T4, T5 and T6 also showed complete inhibition at their recommended doses, while T1 and T7 achieved 82.6% and 91.2% inhibition respectively. At half-recommended doses, T2, T3, T4 and T5 registered the cent per cent inhibition, while T1 and T7 showed 79.2% and 81.9%, respectively. In field trials conducted during kharif, 2020 to 2022 revealed that, the treatment T1 notably reduced sheath blight severity to 36.1%, compared to 61.8% in untreated control and achieved the lowest neck blast severity (6.3%) and realised highest yield (7097 kg/ha) and ICBR (1:7.9), and significantly far surpassing the control yield (5144 kg/ha). The triazole-strobilurins combination demonstrated broad-spectrum efficacy, achieving 62.7% and 18.3% reduction in neck blast and sheath blight respectively compared to standard fungicides. These findings underscore the potential of novel combination fungicides in enhancing disease management and yield while lowering the number of sprays and costs to the rice farmers.