IN VITRO ASSESSMENT OF BIOPESTICIDE BACILLUS THURINGIENSIS VAR. KURSTAKI HD- 1 EFFECTIVENESS ON PHYTOPHTHORA PALMIVORA, AGENT OF COCOA BLACK POD ROT IN CÔTE D’IVOIRE
Phytophthora Palmivora is responsible for the cocoa black pod rot in Côte d'Ivoire, with production losses varying from 20 to 40% depending on the regions. Effectiveness of the environmentally friendly biopesticide Bacillus thuringiensis var. kurstaki HD-1 was evaluated in vitro on the pathogen. The medium pea supercooled has been incorporated with the bioproduct at different concentrations: C1 = 100%, C2 = 50%, C3 =25%, C4 = 12.5% and C5 = 6.25%. This medium into Petri dishes was inoculated either by spreading, with 0.1 mL of P. palmivora inoculum at103 zoospores /mL, or with a mycelial disc of P. palmivora calibrated at 6 mm diameter in the center of the box. The results showed that the germination of zoospores was inhibited at the rate of 100% in the presence of the concentrations C1 and C2. This rate was 74.82 ± 21.53%, 73.17 ± 20.88% and 59.12 ± 39.05%, respectively, for C3, C4 and C5. The efficacy of the bioproduct is revealed by a significant reduction of mycelia growth ranging between 57.77± 2.4 to 100% in the presence of the concentrations C5 to C1. The IC50 of germination was 3.36% of concentration and the IC90 was 43.22%; while those which inhibit 50% and 90% of mycelial growth were 5.67% and 77.94% respectively. The biopesticide Btk HD-1 has a proven fungistatic effect against P. palmivora. Its effectiveness increases with its concentration. So it can be a valuable component of an integrated cocoa black pod management
