Comparative Efficacy of Biofungicides (NECO and ASTOUN) and Synthetic Fungicide against Black Pod Rot of Cocoa Caused by Phytophthora palmivora in Côte d'Ivoire

Abstract

Black pod rot, caused by the oomycete Phytophthora spp., is one of the most important and widespread diseases of cocoa worldwide. In Côte d'Ivoire, production losses are estimated at 25 % to 60 %. The use of synthetic fungicides, which are still dangerous for producers and the environment, remains the most widely practiced method against this pathogen. This study evaluates the efficacy of two plant-based biofungicides, NECO and ASTOUN, in comparison to Callomil super, a conventional fungicide, for managing black pod rot in Côte d'Ivoire. However, the field application rates of these two biofungicides need to be controlled. To this end, a complete randomized Fisher block design was set up with seven treatments (NECO at 5 and 10 ml/l; ASTOUN at 5 and 10 ml/l; Callomil super at 5 and 10 ml/l and controls) and three blocks. Each block was a replicate. The products were applied at 1.7 and 3.4 l/ha in a 332.5 l spray mixture once a month, followed by weekly evaluation of the parameters. A total of three applications were made during the trial. Healthy and diseased pods and cherries were counted to determine black rot rates. A significant difference was observed between treatments for all parameters (P=0.00). The lowest rate (3.00 %) was recorded with NECO at 5 ml/l and the highest rate (6.43 %) with Callomil super at 10 ml/l in 2018. Whereas in 2019, the lowest rate of black rot (4.99 %) was obtained with NECO at 10 ml/l and the highest rate (12.24 %) with ASTOUN at 10 ml/l. In contrast, untreated cocoa trees had a high rate of pod rot during 2018 (15.78 %) and 2019 (22.30 %). NECO at 5 and 10 ml/l, synthetic fungicide at 5 ml/l and ASTOUN at 10 ml/l were more effective in controlling infected pods. It should also be noted that climatic conditions influenced the incidence of black pod rot. The average black rot rate curves varied with the amount of rainfall recorded each week. Temperature and relative humidity varied very little. Rainfall in 2019 was higher (863 mm) than in 2018 (496 mm), as were black rot rates. The biofungicides NECO and ASTOUN have been registered for use against black pod rot in Côte d'Ivoire.