CHI is a foliar spray that improves crop yield, adds resistance to environmental stress, and increases plant vigor. CHI contains chitosan salts, a naturally occurring polymer found in the shells of crustaceans, insects, and many fungi. Research has demonstrated that when plants are exposed to CHI they respond by thickening their cell walls. This increases the plant's resistance to environmental stress and disease while increasing its structural integrity. CHI also induces the activation of genes that stimulate protease inhibitors that help protect against insect attacks.