Dose-response effects of copper, potassium silicate, potassium fosfonate, metalaxil-m and fosetil-al on Phytophthora Mycelial growth in vitro and on chestnut seedlings under greenhouse conditions

European Chestnut (Castanea sativa) is one of several tree species that is affected by Phytophthora root rot. Disease syndrome include root rot that is evidenced above soil by yellow discoloration of leaves, die-back and continuous and severe tree decline. Apoplectic symptoms also occur and tree suddenly collapse during hot weather conditions of summer. Phytophthora root rotting of fruit trees are frequently treated with fungicides which inhibits the growth of pathogens. For chestnut, in Portugal, there is currently no authorized chemical substances for direct control of soilborne Phytophthora species. However, strictly avoidance of disease spread is a basic requisite for disease management of initially localized spots of infected trees which can be largely improved by direct applications of efficient active substances. In this work we focused on the study of direct effects of copper, potassium silicate, potassium fosfonate, metalaxil-M and fosetyl-Al on Phytophthora mycelial growth to improve IDC therapeutic of localized treatment. Crop management still remains the most efficient measure to maintain tree vigor during the long-life span of chestnut trees and conservation tillage methods to reduce inoculum potential and waterborne inoculum spread. A collective management approach integrating all sanitary measure will be necessary to control IDC in chestnut ecosystem.Support was provided by Project BioChestnut-PDR2020-101- 030943 – “Biochestnut-IPM – Implementar estratégias de luta eficazes contra doenças do castanheiro e amendoeira”