The document discusses the antimicrobial properties of chitosan and its applications in plant disease control. Chitosan exhibits antimicrobial activity against viruses, bacteria, fungi and oomycetes. The level of suppression varies based on factors like molecular weight and chemical composition. It has been used as a seed coating agent to improve germination and as a foliar treatment to increase photosynthetic rates in plants. Studies have found chitosan and its derivatives can restrict the growth of pathogens and be effective for controlling plant diseases when applied as a soil amendment or foliar treatment.