Effectiveness of some novel fungicides against the sheath blight pathogen Rhizoctonia solani in rice under in vitro and in vivo conditions

Sheath blight of rice, caused by Rhizoctonia solani, is one of the most aggressive and damaging diseases in rice cultivation, leading to significant crop losses. Consequently, chemical fungicides are the most effective method to inhibit R. solani infection and control this disease. In the present study, R. solani isolate was obtained from infected rice plants, and its pathogenicity was confirmed using Koch’s postulates on 20-day-old rice seedlings at three different inoculum levels. The lowest percent disease index and disease incidence were recorded with the 1 ml pathogen inoculum suspension, while the 2 ml and 3 ml suspensions resulted in 100% disease incidence, significantly affecting plant parameters. Furthermore, five different fungicides, Duphetar Plus, Evito, Nativo, Ridomil Gold, and Shincar, were evaluated at three concentrations (10, 100, and 1000 ppm) against R. solani using poisoned food method. The results revealed that two fungicides, Shincar and Nativo, resulted in maximum mycelial growth inhibition of R. solani, whereas the other fungicides failed to inhibit the mycelial growth of the pathogen at all concentrations. Shincar and Nativo were further tested in a greenhouse setting to control pathogen infection in rice plants. These fungicides showed excellent results, reducing R. solani infection and minimizing disease incidence in treated rice plants compared to the control. The highest root length, shoot length, and plant weight were observed with Shincar, followed by Nativo. It is suggested that the use of these fungicides may reduce sheath blight disease incidence, effectively control pathogen infection, and improve plant growth parameters in field conditions.