Moreover, the disease control effects of chitosan and oligochitosan were concentration-dependent and weakened over inoculated time. The IC50 of chitosan on disease incidence caused by A. kikuchiana was 1.32 g/L after inoculation 72 h, 7.94 g/L after inoculation 96 h and 10.7 g/L after inoculation 120 h, meanwhile the IC50 of oligochitosan was 1.75 g/L after inoculation 72 h and 10 g/L after inoculation 96 h (Table 3).