Chemical Management of Anthracnose-Twister (Colletotrichum gloeosporioides Penzig and Sacc-Gibberella moniliformis Wineland) Disease of Onion (Allium cepa L.)

Among all other diseases of onion, anthracnose-twister caused by Colletotrichum gloeosporioides and Gibberella moniliformis remained the most destructive every cropping season. It destroys onion production especially when left unmanaged. Studies showed that chemical management is still the best option in addressing this disease, thus this study was conducted. It aimed to: (a) evaluate the different protectant fungicides available in the market in managing the disease; (b) test Paclobutrazol in suppressing the rapid production of gibberellic acid that triggers the development of the disease; and (c) compare the performance of Paclobutrazol and other fungicides in suppressing the disease when applied as preventative and curative.

                  Results showed that onion plants treated with Captan and Paclobutrazol had the least incidence of disease under protective spray application while onion plants applied with Carbendazim and Paclobutrazol had the least severity on both spray applications. Whereas, onion plants applied with Difenoconazole-Propiconazole and Auxin showed the highest disease incidence and severity in both spray applications. The shortest length of neck was observed in onion plants treated with Benomyl+Paclobutrazol and Paclobutrazol alone, while the longest was observed in Difenoconazole-Propiconazole. The highest yield was obtained in onion plants treated with Carbendazim+Paclobutrazol and Captan, whereas the lowest yield was obtained in onions applied with Auxin and Difenoconazole-Propiconazole.

                Protective spray application obviously showed lower disease incidence and severity, shorter neck and higher yield compared to curative spray application.