Scrutinizing the efficacy of plant extracts and bactericidal agents applied against Xanthomonas axonopodis, the causative agent of bean blight

Common bean (a major staple seed crop and legume) is susceptible to bean blight (Xanthomonas axonopodis). The study controlled bean blight in the laboratory and screen-house using botanicals and bactericides. Completely randomized and replicated design was used and recorded percentage germination, number of leaves, shoot length, seed weight, shoot fresh weight, disease incidence, and severity. In vitro, control of the pathogen depended on the application of antibiotics: tetracycline, cephalosporin, lincomycin, and erythromycin in order of efficacy, giving 52.2–100 % inhibition of the pathogen. In vitro, aqueous extracts of Eucalyptus globulus, Aframomum melegueta, Ricinus communis, and Acmella oleracea effectively inhibited 25.0–62.5 % of the bacterial growth. In screen-house, effects of chemical bactericides on Xanthomonas species revealed a significant difference in the number of leaves at 49 days after inoculation (DAI). Also, percentage inhibition of Xanthomonas species by the bactericides ranged from 46.2-97.5 % from 6-56 DAI. Shoot lengths were significantly different under the influence of plant extracts at 35 DAI and 49 DAI. Plant extracts caused 36.4-90.9 % percentage inhibition of the pathogen from 6-56 DAI. Formulation of agricultural applications using these control agents is required.