RootShield WP from BioWorks has been approved by the Organic Materials Review Institute (OMRI) for use in organic production. RootShield WP provides preventive control for up to 12 weeks per application of major root diseases including Pythium, Fusarium, Rhizoctonia, Thielaviopsis and Cylindrocladium. This patented hybrid fungus Trichoderma harzianum ( strain T-22) grows on roots, protecting them against damaging fungi. RootShield WP is registered for indoor and outdoor root disease control on greenhouse and outdoor ornamentals, herbs and vegetables. It has a 0-hour REI.