Propineb efficiency in controlling downy mildew of onion under field conditions

Downy mildew of onion has worldwide occurrence. This study aimed to evaluate the effect of weekly sprays of different active ingredients on the area under a disease progress curve (AUDPC) and on the commercial yield of onion, under field conditions. We observed that propineb sprays resulted in the highest values of yield in 2017 (32.98 t ha−1) and 2018 (20.70 t ha−1). Propineb (130.66) and metalaxyl-M + mancozeb (144.66) presented the lowest AUDPC values in 2017. Metalaxyl-M (100 g ha−1) + mancozeb (1600 g ha−1), bentiavalicarb-isopropyl (56.25 mL ha−1) + chlorothalonil (562.5 mL ha−1) and bentiavalicarb-isopropyl (40 mL ha−1) + fluazinam (100 mL ha−1) resulted in higher yields than the control (water) in the two years of testing. We emphasise the importance of using fungicides with protective action to control downy mildew of onion.