ABSTRACT
The antibacterial activity of methanol leaf extract of Psidium guajava L. was performed on six plant pathogenic bacteria, namely Xanthomonas citri, Xanthomonas euvesicatoria, Xanthomonas oryzae, Xanthomonas oryzicola, Pectobacterium carotovorum and Pectobacterium chrysanthemi by cup-plate agar diffusion method. Different concentrations gave different range of means diameter inhibition zones where at concentrations o f 25, 50, 100 and 200 mg/ml, the range was 10.00±0.00 mm to 15.00±0.00 mm, 12.00±0.00 mm to 17.00±0.00 mm, 15.00±0.00 mm to 20.00±0.00 mm and 16.00±0.00 mm to 25.00±0.00 mm, respectively. X. oryzae gave the highest mean diameter inhibition zone when tested with all concentrations compared to the mean diameter inhibition zones of other plant pathogenic bacteria. The minimal inhibitory concentration (MIC) of the methanol extracts was performed by macrobroth dilution technique and the lowest concentration used that was still able to inhibit the bacterial growth was 0.391 mg/ml for X. oryzae.