Efficacy of spraying intervals of Ridomil Plus 66 WP for control of taro leaf blight disease

Abstract

Taro leaf blight causes up to 100% yield loss in susceptible taro (Colocasia esculenta L. (Schott)) cultivars. The use of fungicides in disease management is fast and effective; however efficacy of fungicides could be affected by frequency of application. The objective of this study was to evaluate the efficacy of spraying intervals and economic benefits of Ridomil Plus 66 WP (12% Metalaxyl-M and 60% Copper (1) oxide) on taro leaf blight disease. The study consisted of four fungicide spraying intervals, viz at one, two and at four weekly intervals, all at the concentration of 3.3 g l-1 and no fungicide application as the control. Results showed no significant differences (P > 00.5) between one and two weekly spraying intervals in terms of taro leaf blight disease incidence and severity. These were, however, significantly different (P < 0.05) from four weekly and no fungicide applications. Taro corm yield was higher in weekly spraying interval, but not significantly different (P > 0.05) from biweekly application intervals. Yields in weekly intervals were 2.9, 33.0 and 44.0% higher than biweekly, four weekly and no application intervals. Applying fungicide at a biweekly interval was found to be economically efficient as it recorded higher total revenue and net present values. Applying 66 WP (12% Metalaxyl-M and 60% Copper (1) oxide) at 2 weekly interval was the optimum period and most efficient to reduce the incidence and severity of Phytophthora leaf blight disease and increase yield of taro.