Copper Gluconate as an Ecofriendly Compound Protecting Apple and Orange Trees against the Most Common Pathogens Affecting Them during the Pre-harvest Stages

Abstract

Objective: The aim of this study was to investigate the efficacy of liquid copper (Cu) complexed with gluconic acid as an alternative to classical treatments based on large amounts of inorganic Cu, and to determine the efficacy of Cu gluconate in apple (Malus domestica) against bacterial and fungal pathogens, Erwinia amylovora, Venturia inaequalis, and Monilinia fructicola, as well as in orange (Citrus sinensis) against fungal pathogens, Alternaria alternata and Phytophthora citrophthora. Methods: Applications of Cu gluconate were performed by foliar applications when the first symptoms of the diseases were detected. The doses tested of Cu gluconate were 3mL/L, 4mL/L, and 5mL/L compared to absolute control and a reference commercial product, namely Cu sulfate pentahydrate 25% at 3L/ha. Evaluations were conducted regarding the development of infection and the effectiveness of the treatment. After the first and second applications of this compound, the efficacy of the compound was evaluated. Results: It was found that the higher dose of Cu gluconate (5mL/L) provided the best efficacy in controlling the infection, with no difference in efficacy between the reference commercial product and Cu gluconate. Conclusion: It was concluded that Cu gluconate is an effective alternative for the control of bacterial and fungal diseases in apple trees and orange trees, with the advantage of reducing the levels of Cu in the environment as well.