Integrated disease management of sheath blight in rice using bio-agents and fungicides

Abstract:

Sheath blight, caused by Rhizoctonia solani Kühn, destroys an estimated 6–12% of rice yield worldwide every year, and sole reliance on fungicides is neither sustainable nor consistently effective. This research evaluated seven integrated management treatments combining bio-control agents (Trichoderma harzianum, Pseudomonas fluorescens) and a systemic fungicide (hexaconazole 5% SC) against sheath blight in irrigated rice at the Bluegrass Agricultural Institute, Lexington, Kentucky, during two consecutive growing seasons (2022 and 2023). Treatments were arranged in a randomised complete block design with four replications. Disease severity index (DSI) was recorded at 30, 45, 60 and 75 days after transplanting (DAT). The triple combination of T. harzianum + P. fluorescens + hexaconazole achieved the lowest DSI at every time point, reaching 7.3% at 75 DAT compared with 63.2% in the untreated control. Among dual combinations, T. harzianum + hexaconazole performed best (DSI 9.7% at 75 DAT), followed by P. fluorescens + hexaconazole (10.8%). Sole bio-agent applications reduced DSI to 21.8–23.4% at 75 DAT a meaningful reduction but not enough for commercial acceptability. Grain yield mirrored the disease data: the triple combination produced 5.61 t ha⁻¹, which was 61.7% more than the control (3.47 t ha⁻¹). The results indicate that combining bio-agents with a reduced-rate fungicide spray can match or surpass the performance of full-rate fungicide alone while lowering chemical inputs.