Evaluation of fungicides and biocontrol products for the control of Phytophthora root rot of hydrangeas

Phytophthora root rot is one of the most important diseases in almost all hydrangeas of nursery production. In this study, the efficacy of fungicides and biocontrol products against Phytophthora root rot of hydrangea was assessed in greenhouse and field experiments. Treatments used in field or greenhouse experiments were RootShield PLUS+, MBI110, IT-5103, Grotab, OxiPhos, TerraClean 5.0 + TerraGrow program, Segovis, Pageant Intrinsic, Empress Intrinsic and Subdue Maxx. Pots/plots were inoculated with Phytophthora nicotianae grown on rice grains, sterilised rice grains were used for negative controls. After the trials, plant growth data (total plant weight, root weight, plant height, plant width) were recorded, and roots were assessed for disease severity using a scale of 0-100%. The treatments most effective in reducing Phytophthora root rot severity were Segovis, Empress Intrinsic, Subdue Maxx, TerraClean 5.0 + TerraGrow program in both greenhouse and field experiments. This study will help nursery producers make proper management decisions by using recommended fungicides and biocontrol products of this study in a rotation or alone to manage Phytophthora root rot of hydrangea.