Effective management of white rust disease in red amaranth: a field study in Dhaka, Bangladesh

Abstract: This study aimed to evaluate the effective management strategies of Albugo candida, a pathogen of white rust disease in red amaranth (Amaranthus tricolor L.), accountable for the reduction of seed production. The study was performed during the Rabi season of 2018 and the Kharif season of 2019 at Sher-e-Bangla Agricultural University in Bangladesh. Eight treatments, including chemical, botanical, and biopesticide treatments such as Ridomil Gold 68 WG, Autostin 50 WP, Dithane M 45, Goldton 50 WP, the Bordeaux mixture, G-Derma, Garlic bulb extract, and Allamanda leaf extract, were evaluated. Four foliar sprays were applied at seven-day intervals after disease symptom onset. The field experiments followed a randomized complete block design with three replications. A microscopic study confirmed that Albugo candida was the causal organism. In both seasons, Ridomil Gold demonstrated superior efficacy in reducing disease incidence in plants, disease incidence in leaves, and disease severity, which were 63.07%, 62.78.5, and 84.31%, respectively, in Rabi and 69.73%, 65.71%, and 88.41%, respectively, in the Kharif season. Allamanda leaf extract also had statistically similar results, while Autostin exhibited promising effectiveness. Furthermore, compared with the other treatments, the combination of Ridomil Gold and Allamanda leaf extract significantly enhanced the growth parameters and seed yield in both seasons. Assessing the collective effectiveness of the treatments, Ridomil Gold demonstrated the most efficient control of white rust disease. Consequently, Ridomil Gold holds promise for application in red amaranth seed production. Additionally, the use of Allamanda leaf extract is an environmentally friendly approach to white rust disease management and promotes safer crop production practices. This study offers significant guidance to practitioners seeking optimal disease management strategies.