HYSHIELD™ Plant Immune Activator — 20 Litres (5.28 gal) From the creators of Hygrozyme comes HYSHIELD™ — a natural plant defense activator formulated with chitosan, a biopolymer derived from recycled crustacean shells (crab and shrimp exoskeletons). Chitosan triggers a plant's systemic acquired resistance (SAR), essentially tricking the pl...