Contribution à l'amélioration de la lutte contre la pourriture brune des cabosses de cacaoyer : Influence des facteurs agro-écologiques sur la dynamique des populations du Phytophthora SPP. en Haïti, cas de la commune de Port-Margot

Abstract

The brown rot on which our study is based was the most widespread and the most damaging in the commune with a statistically higher incidence in the Bas-Quartier (29%) than the Petit-Borgne (26%) and the Coral (24%). In order to contribute to the improvement of the control of this disease due to species of the genus Phytophtora spp., a survey of producers and laboratory tests were carried out. The results obtained have identified two main factors that are at the origin of the population density of Phytophtora spp: pedoclimatic factors (presence of inoculum of Phytophtora spp in the soil, rainfall episodes, luminosite) and cultivation operations carried out by cocoa farmers in Port-Margot (pruning, sanitary pruning, weeding, shade management...) Pathogen isolates obtained from symptomatic pods collected from plots in Port-Margot have been morphologically identified as belonging to one of the two species of Phytophtora spp: P. capsici or P. palmivora. The results of comparisons of these isolates with the five strains of Trichoderma asperellum (C306, PR10, PR11, PR12, 659-6) in vitro revealed a non-significant inhibitory effect at the 5% threshold (P>0.05), that the five strains of T. asperellum had the same antifungal activity against both Phytophtora spp. But statically different between PR12 and C306 (27oC) for direct confrontation at 22oC and between the factors studied (T. asperellum x Phytophtora spp) in indirect confrontation. In fact, the results of confrontations (pathogen - antagonist) showed an antagonistic effect, especially in the interpenetration zone between Trichoderma spp. and Phytophthora spp. In fact, the strains of T. asperallum evaluated showed interesting potential in the control of P. capsici and P. palmivora as biological control agents. The different strains have produced potential antibiotics (volatile metabolites, diffusible non-volatile metabolites), competitive and have the ability to thwart, parasitize pathogens (P. capsici and P. palmivora). But, the different strains have the same antifungal activity against both Phytophtora spp maintained at 22oC and 27oC according to statistical analyses.