This study aims at screening and testing for effects of aqueous plant extracts on rice bacterial leaf blight (Xanthomonas oryzae pv. oryzae) and investigating disease reduction mechanisms. Except Cymbopogon citratus, all extracts tested did not give observable adverse effects on seed germination and development. Under greenhouse conditions, seed soaking with Kalanchoe pinnata extract showed the highest effects until 21 days after pathogen inoculation. The effects involved induced resistance. Activities of the defense-related and antioxidant enzymes (peroxidase, catalase, polyphenol oxidase and phenylalanine ammonia-lyase) increased after pathogen inoculation and extract treatment. Furthermore, the extract showed a direct inhibitory effect on the pathogen.