Isolation of the Pathogenic Organism of Bacterial Blight of Psidium guajava and the Antibacterial Effects of Aqueous Ethanolic Leaf Extracts of Ocimum gratissimum, Cymbopogon citratus, Vernonia amygdalina and Annona muricata on the Pathogen

The research work was aimed at isolation, characterization and identification of pathogenic organism responsible for the infection of guavas (Psidiumguajava) referred to as bacterial blight of guava and also the antibacterial potency of ethanolic leaf extracts of Vernoniaamygdalina, Ocimumgratissimum, Cymbopogoncitratus and Annonamuricata were screened against bacterial blight isolate (Erwiniapsidii) using agar disk diffusion method. The leaf extracts were screened for antibacterial activities at 200mg/ml concentration. Antibacterial efficacy of extracts against the bacterial isolate was indicated by the appearance of clear zones of inhibition around the disks. The extracts of Vernoniaamygdalina and Ocimumgratissimum showed inhibitory activities against the bacteria isolate with zones of inhibition of 13mm and 9mm respectively while extracts of C.citratus and A.muricata showed no zone of inhibition. Result of the antagonistic activity of the extracts compared favourably with the activity of standard fumigant. The minimum inhibitory concentration of V.amygdalina and O.gratissimum were 25mg/ml and 50mg/ml respectively and not determined in C.citratus and A.muricata.