Harnessing stable and effective novel combination seed treatment fungicides and biocontrol agent for sustainable management of Rhizoctonia root rot in soybean

Rhizoctonia root rot is a threat due to wide host range and lack of resistant soybean cultivars. Field experiments were conducted across 15 environment-years (five sites, 2019–2021). The study evaluated the efficacy and stability of three distinct combination fungicides, carboxin + thiram, trifloxystrobin + penflufen and thiophanate-methyl + pyraclostrobin, along with a biocontrol agent, Trichoderma harzianum under inoculated conditions. All treatments significantly reduced Rhizoctonia root rot, enhanced plant growth, stabilised yield and improved benefit–cost ratios compared with the control. Across environments showed that thiophanate-methyl + pyraclostrobin and trifloxystrobin + penflufen provided superior disease suppression and yield improvement. Multi-trait analysis integrating disease severity and plant growth parameters per plant identified stable performance across environments. Location-specific analysis identified as highly discriminating environments. These results supply environment-specific recommendations and endorse seed-dressing fungicides and biocontrols as economical tools for sustainable management of Rhizoctonia root rot in soybean.