The aim of studies to find out which parts of Ageratum conyzoides or kinds of leaf neem extract hd abiliry of induced resistance against blast disease. Experiments were conducted on rice cultivar OM 4218 at Cantho Univrsity, with randomized completed design including 7 treatments and 5 replications. Plant extracts 4% treated by seed soaking and spraying at 15 days after sowing (DAS) fungal inoculation at 20 DAS. Percent of leaf blast disease was recorded at 5 and 14 days after inoculation (DAI) based on scale of Pinnschmidt et al (1993). Sporulation was counted at 5 and 7 DAI. Results showed that treatments of seed soaking and spraying by either stem of Ageratum conyzoides or old leaf neem had good effect on disease suppression and limitation of sporulation.