Malaysian Journal of Sustainable Agriculture (MJSA)

A field experiment was conducted in Chaurjahari Municipality, Rukum-west, Nepal during the rabi season of 2019 to study the management of purple blotch complex of onion through chemicals and bio fungicides. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications of each treatment. Six different chemical fungicides; Hexaconazole, Tebuconazole, Mancozeb+Cymoxanil, Dimethomorph, Chlorothalonil, Carbendazim and one biological fungicides Trichoderma were evaluated in field condition against Alternaria porri and Stemphylium vesicarium for effective control of purple blotch complex. The fungicides were spread in fortnight interval and data were collected on biometric parameters like plant height, number of umbel stalk, umbel diameter; yield contributing characters like thousand seed weight and yield of onion. Likewise, data on disease incidence and disease severity were also recorded. Hexaconazole and Mancozeb + Cymoxanil were proved to be best in controlling this complex with the Percent Disease Control (PDC) of 84.45 percent and 80.00 percent respectively. The highest yield 878.7 kg/ha and thousand seed weight 3.72gm were recorded from Hexaconazole treated plot followed by Mancozeb + Cymoxanil with yield and thousand seed weight of 878.3kg/ha and 3.64gm respectively. The economic analysis of fungicides was also done where Hexaconazole at 0.1 percent concentration was found most economic with the Benefit Cost ratio of 3.02. Similarly, the study of weather parameter in relationship to disease occurrence was done, the coefficient of multiple determinants (R2) obtained was 0.7858 indicating 78.58 percent of variation in purple blotch development explained by the different weather parameter under study.