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.La br\ufblure des feuilles de taro peut causer une perte de rendement allant jusqu\u2019\ue0 100% chez les cultivars sensibles de taro ( Colocasia esculenta L. (Schott)). L\u2019utilisation de fongicides dans la gestion des maladies est rapide et efficace; cependant, l\u2019efficacit\ue9 des fongicides pourrait \ueatre affect\ue9e par la fr\ue9quence d\u2019application. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer l\u2019efficacit\ue9 des intervalles de pulv\ue9risation et les avantages \ue9conomiques de Ridomil Plus 66 WP (12% de m\ue9talaxyl-M et 60% d\u2019oxyde de cuivre (1)) sur la maladie du taro. L\u2019\ue9tude consistait en quatre intervalles de pulv\ue9risation de fongicide, c\u2019est-\ue0-dire \ue0 une, deux, quatre intervalles hebdomadaires, le tout \ue0 la concentration de 3,3 g l-1 et sans application de fongicide. Les r\ue9sultats n\u2019ont montr\ue9 aucune diff\ue9rence significative (P> 00,5) entre un et deux intervalles de pulv\ue9risation hebdomadaires en termes d\u2019incidence et de gravit\ue9 de la br\ufblure du taro. Celles-ci \ue9taient cependant significativement diff\ue9rentes (P <0,05) de quatre applications hebdomadaires et sans fongicide. Le rendement en corme de taro \ue9tait plus \ue9lev\ue9 dans l\u2019intervalle de pulv\ue9risation hebdomadaire, mais pas significativement diff\ue9rent (P> 0,05) des intervalles d\u2019application bihebdomadaires. Les rendements \ue0 intervalles hebdomadaires \ue9taient de 2,9, 33,0 et 44,0% sup\ue9rieurs \ue0 ceux des deux semaines, quatre semaines et aucun intervalle d\u2019application. L\u2019application d\u2019un fongicide toutes les deux semaines s\u2019est av\ue9r\ue9e \ueatre \ue9conomiquement efficace car elle a enregistr\ue9 des revenus totaux et des valeurs actuelles nettes plus \ue9lev\ue9s. En conclusion, l\u2019application de 66 WP (oxyde de m\ue9talaxyl-M \ue0 12% et oxyde de cuivre (1) \ue0 60%) \ue0 intervalles de 2 semaines s\u2019est av\ue9r\ue9e \ueatre la p\ue9riode optimale et la plus efficace pour r\ue9duire l\u2019incidence et la gravit\ue9 de la maladie phytophthora et augmenter le rendement du taro