After 5 d of incubation, colonies of S. sclerotiorum grew up to 7.87 cm in diameter on potato dextrose agar while the diameter of chitosan-treated colonies was only 0.92 cm , and the growth inhibition rate reached 88.31%. my celial biomass wass also strongly inhibited by 1% chitosan (Fig.1-B). The mycelial biomass of untreated cultures in-creased dramatically during the first 2 d of incubation in PDB. In contrast,mycelial biomass remained at a low level and 1% chitosan . And the growth inhibition rate increased to 97.40% after 2 d of incubation