Antibacterial Effects of Aqueous Ethanolic Leaf Extracts of Ocimum gratissimum, Cymbopogon citratus, Vernonia amygdalina and Annona muricata on the Isolated Pathogenic Organism of Citrus Canker from Citrus sinensis (Sweet Orange)

The aqueous ethanolic extracts of Vernonia amygdalina, Ocimum gratissimum, Cymbopogon citrates and Annona muricata were screened for antibacterial activities at 200mg/ml concentration. Antibacterial efficacy of extracts against the bacteria were identified by gram staining techniques, coagulase and catalase tests and the bacterial isolate was indicated by the appearance of clear zones of inhibition around the disks. The extracts of Vernonia amygdalina and Ocimum gratissimum showed inhibitory activities against the bacterial isolate with zones of inhibition of 12mm and 8.5mm respectively while extracts of C.citratus and A.muricata showed no zone of inhibition. Result of the antimicrobial activity of the extracts compared effectively with the activity of standard fumigant with extract of V. amydalina showing the highest potency which was used in preparation of a local fumigant. The minimum inhibitory concentration of V.amygdalina and O.gratissimum were 25mg/ml and 50mg/ml respectively which were not determined in C.citratus and A.muricata. In conclusion, the results of this investigation showed that the aqueous ethanolic leaf extracts of V. amygdalina and O. gratissimum can be used as an effective control measure for the elimination of citrus canker of Citrus sinensis.