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Bacterial spot disease caused by Xanthomonas axonopodis pv. vesicatoria is an important seed-borne disease of pepper and tomato. Antibacterial effects of aqueous extracts of radish (Raphanus raphanistrum), garlic (Alium sativum), mint (Mentha piperita), onion (Allium cepa), marata (Clematis marata), oleander (Nerium oleander), rosmary (Rosmarinus officinalis), eucalyptus (Eucalyptus sp.), pepper tree (Schinus sp.), terebinth tree (Pistacia terebinthus) and pine tree (Pinus sylvestris) were investigated in-vitro and in-vivo experiments for the bacterial disease agent X. a. pv. vesicatoria. Two different extract sterilization methods, autoclaving and filtering, were used in-vitro experiments. No growth inhibitions were recorded with the aqueous extracts of radish, mint, onion, maratha, oleander, rosemary, peppertree, terebinth tree and pine tree. Garlic and eucalyptus extracts, however, showed antibacterial activity in vitro experiments. Although filtered-sterilized garlic extract was effective on the growth of pathogen, autoclaved-sterilized garlic extract did not show antibacterial effect. This result clearly indicates that inhibitory compound(s) of garlic was thermolabile. Aqueous extracts of eucalyptus and garlic were very effective to reduce the seed-borne inoculum source of the disease in-vivo conditions. Eucalyptus extract was found to the best seed treatment. Symptom development on pepper and tomato seedlings was completely inhibited by eucalyptus extract as a seed treatment. Disease incidence was reduced at ratios of 95 and 86% by filtered-sterilized garlic extract on tomato and pepper seedlings, respectively. Similarly, disease severity on tomato and pepper seedlings was reduced between 77 and 96% at ratios by garlic and eucalyptus extracts, respectively. This study clearly demonstrated that aqueous garlic and eucalyptus extracts are effective seed treatments against seed-borne infections of bacterial spot disease of tomato and pepper for traditional and organic seedling production