The second assay for antifungal activity of COS was the agar diffusion method. Mycelial disks (diameter 5 mm) were cut from the periphery of 14-day fungal culture, and placed in the center of Petri dishes (100 mm × 15 cm) containing 20 ml SDA with COS (final concentration 0% (control), 0.1%, 1%, or 5%).