UAV-based application of fungicides for management of blast disease in rice: comparative evaluation with manual spraying at recommended and reduced doses

Rice blast, caused by Magnaporthe oryzae , is a widely distributed and most destructive disease in rice cultivation, threatening global food security. Farmers are increasingly adopting Uncrewed Aerial Vehicles (UAVs) for pesticide application in rice with reduced doses. However, scientific evidence-based fungicide dose reduction under UAV-assisted spraying remains limited in India. A field experiment was conducted over two crop growing seasons ( kharif , 2022 and rabi , 2022-23) at one location to evaluate the control efficacy of two combination fungicides i.e. , Azoxystrobin + Tricyclazole, Azoxystrobin + Difenoconazole, and one regularly used fungicide, Tricyclazole 75% WP against blast, applied through UAV’s at recommended (100% @ 1X) and reduced dosages (75% @ 0.75X) and compared with their corresponding application using the knapsack power sprayer (100% @ 1X). Disease severity, control efficacy, grain yield, economic returns, and phytotoxicity were assessed under field conditions during both the seasons. The application of conventional fungicides using UAV at the recommended dosage (1X) consistently exhibited better control of leaf and neck blast than the corresponding reduced-dose UAV treatments (0.75X) and conventional knapsack power spraying (1X), with the effect is being more pronounced against neck blast under field conditions. Of the fungicides, Azoxystrobin 16.7% + Tricyclazole 33.3% SC and Azoxystrobin 18.2% w/w + Difenoconazole 11.4% w/w SC applied through UAVs at 1X dosage recorded the highest disease control efficacy, grain yield, and economic returns. This study represents one of the first systematic preliminary field evaluation of fungicide dose optimized under UAV-assisted spraying in India using currently registered conventional formulations without adjuvants while maintaining the active ingredient dose ( g a.i . ha - ¹).