Management of spot blotch using fungicidal combinations in wheat (Triticum aestivum L.)

Abstract

Spot blotch caused by Bipolaris sorokiniana has been a devastating disease for wheat cultivation in Eastern gangetic plains (EGP) of India and South Asia. Most released wheat varieties fall under Moderate Resistant to Moderate Susceptible scale. Limited studies have been performed to understand the yield penalty due to the disease severity. This study was conducted at the Bihar Agricultural University, Sabour, Bihar, during the Rabi 2021-22 and 2022-23. The major objective was to evaluate the efficacy of fungicides in combination against wheat spot blotch in terms of yield advantage under in vitro and in vivo conditions. Eight fungicidal combinations were tested including tebuconazole 50% + trifloxystrobin 25% WG, propiconazole 13.9% + difenoconazole 13.9% EC, azoxystrobin 12.5% + tebuconazole 12.5% SC, and mancozeb 75% WP at four level of doses. In vitro results showed complete fungal growth inhibition by all four combinations at 100 ppm, while at 75 ppm, tebuconazole 50% + trifloxystrobin 25% WG achieved the highest inhibition (91.84%). Field trials conducted over two years revealed that tebuconazole 50% + trifloxystrobin 25% WG at 1 g/liter was the most effective in reducing disease severity, with the lowest infected plant (35.33 and 38.67/m²), disease incidence (10.76% and 12.33%), and percent disease index (9.63% and 10.33%). This treatment has also achieved the maximum disease reduction (81.69% and 80.96%) resulting 28.91% and 27.46% yield increase over control in 2021-22 and 2022-23, respectively. The study concludes that tebuconazole 50% + trifloxystrobin 25% WG @ one g/litre is highly effective for managing spot blotch.