| Summary: | The aim of this work was to investigate the most promising natural antimicrobials effective for the growth suppression of <i>Xanthomonas</i> spp. bacteria. The research objects were <i>Xanthomonas</i> spp. strains isolated from tubers and stem of plants growing in Lithuania: <i>Xanthomonas translucens</i> NRCIB X6, <i>X. arboricola</i> NRCIB X7, NRCIB X8, NRCIB X9, and NRCIB X10; the supernatants of lactic acid bacteria <i>Lactococcus lactis</i> strains 140/2, 57, and 768/5, <i>Lactobacillus helveticus</i> strains 14, 148/3, R, and 3, <i>Lb. reuteri</i> 3 and 7, <i>Streptococcus thermophilus</i> 43, <i>Enterococcus faecium</i> 59-30 and 41-2; endophytic bacterial strains <i>Bacillus</i>, <i>Pseudomonas</i>, and <i>Paenibacillus</i> spp.; and essential oils of lavender (<i>Lavandula angustifolia</i>), grapefruit (<i>Citrus paradisi</i>), pine (<i>Pinus sylvestris</i>), thyme (<i>Thymus vulgaris</i>), rosemary (<i>Rosmarinus officinalis</i>), peppermint (<i>Mentha piperita</i>), lemon (<i>Citrus limetta</i>), aqueous extracts of blueberries (<i>Vaccinium myrtillus</i>), and cranberries (<i>Vaccinium vitis-idaea</i>). The antimicrobial activity of tested substances was determined by agar diffusion method. Supernatants of <i>Lb. reuteri</i> strain 7 and <i>Lb. helveticus</i> strains 14, R, 3, and 148/3 were found to have a high antimicrobial activity against <i>Xanthomonas</i> spp. bacteria strains when compared to the positive control—1.0% copper sulfate (diameter of inhibition zones was 28.8 ± 0.7 mm). The diameter of inhibition zones of supernatants ranged from 23.3 ± 0.6 mm to 32.0 ± 0.1 mm. Thyme (2.0%) and lavender (2.0%) essential oils inhibited the growth of <i>Xanthomonas</i> spp. strains. The diameter of the inhibition zones was from 14.7 ± 0.8 mm to 22.8 ± 0.9 mm. The aqueous extracts of blueberries had a weak antimicrobial activity. The diameter of inhibition zones ranged from 11.0 ± 0.2 mm to 13.0 ± 0.2 mm.
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