Evaluation of fungicide combinations for the management of brown spot disease of rice

Rice is a primary food for more than half of the global population and plays a crucial role in sustainable food security worldwide. However, brown spot disease of rice caused by Bipolaris oryzae is increasingly threatening its production and productivity. To address this challenge, seven fungicide combinations were evaluated for their efficacy against B. oryzae under in vitro conditions using the poisoned food technique and field conditions during the kharif seasons of 2023 and 2024. In vitro studies showed that among seven fungicide combinations tested at four different concentrations (i.e. 100 ppm, 150 ppm, 200 ppm and 250 ppm) and three replications, azoxystrobin 5.1 % + tebuconazole 9.1 % + prochloraz 18.2 % EC was the most effective achieving complete fungal growth inhibition at 200 ppm, followed by tebuconazole 50 % + trifloxystrobin 25 % WG (complete inhibition at 250 ppm). Kasugamycin 5 % + copper oxychloride 45 % WP was the least effective with a maximum inhibition of 63.89 %. Field trials confirmed these results. Azoxystrobin + tebuconazole + prochloraz EC recorded the highest disease reduction (66.97 %) with the lowest PDI (16.67 %) and maximum yield (57.30 quintals per hectare (q ha-1); 76.13 % increase over the control. Tebuconazole + trifloxystrobin WG performed similarly with 54.68 % disease reduction and a yield of 54.00 q ha-1 (66.00 % increase in yield over the control). Kasugamycin + copper oxychloride WP showed the lowest efficacy (18.75 % disease reduction; 23.89 % increase in yield over the control). The results indicate that azoxystrobin + tebuconazole + prochloraz EC and tebuconazole + trifloxystrobin WG are promising combinations for effective management of brown spot disease in rice.