Antibacterial Activities of Euphorbia hirta and Lantan camara Extracts on the Growth of Some Bacteria that Causes Banana Plant Disease

Bananas (Musa acuminata L.) are confronted with a number of challenges imposed by bacterial diseases which lead to huge yield losses.  In order to improve the yields of the banana plantation, one of the recommended management strategies which would be inexpensive and environmentally friendly was developed. The objective of this study was to improve the sanitary state of banana plant. To achieve this objective, bacteria associated with the different banana organs were isolated on Nutrient Agar (culture medium) and their morphological identification was carried out based on the cultural characteristics and the colour of the bacterial walls observed under an optical microscope and using reference documents (bacteriological identification keys).  Antibacterial activity of Lantana camara and Euphorbia hirta extracts were evaluated in vitro on agar medium aginst Xanthomonas campestris pv. Pseudomonas solanacearum and Ralstonia solanacearum. The results showed that the banana plant harbours a diversity of bacteria species, the most frequent being Ralstonia solanacearum as it was isolated from all infected organs. The yields of the equeous extacts of Euphorbia hirta and Lantana camara were particularly high (7% and 13%) respectively, compared to those of the ethanolic extracts which were lower. Aqueous extracts of Euphorbia hirta, at 50 mg/ml, had bactericidal activity against Ralstonia solanacearum and Pseudomonas celebensis. Aqueous extracts of Lantana camara, at concentrations of 25 mg/ml and 50 mg/ml, exhibited bactericidal activity against P. celebensis. Meanwhile, the ethanolic extracts of L. camara, at 50 mg/ml had bacteriostatic activity against the development of P. celebensis. Ethanolic extracts of E. hirta had bactericidal activity on the growth of Xanthomonas campestris at 25 mg/ml and 50 mg/ml. The same activity was obtained with P. celebensis at 50 mg/ml. These results suggest that the aqueous and ethanol extracts of the tested plants at high concentrations could be used as alternatives to chemical products in the fight against banana diseases especially Xanthomonas, Pseudomonas and Ralstonia. Hence further studies need to be undertaken in order to isolate the active compounds from these extracts with bactericidal potential.