Abstract: The effects of biological agent HY01 on seedling main diseases of cucumber（Cucumis sativus L.） was investigated. The results showed that the incidence of seedling damping-off and rhizoetonia rot was reduced by 94.8% and 92.7%,respectively,which were significantly higher than that of chemical fungicide treatment. Compared to the water control and chemical fungicide,some index including plant height,root length and root number of seedlings cucumber were significantly increased. Laboratory toxicity test showed that HY01 had only weak antibacterial effect and not enough to produce bactericidal effect in the field. it was suggested that biological agent HY01 significantly improved the disease resistance of cucumber seedling by inducing plant resistance,and also had obvious effect of promoting plant growth.

Key words: biological agent, cucumber（Cucumis sativus L.） seedling, damping-off, rhizoetonia rot, toxic test