Comparison of the effectiveness of several commercial products and two new copper complexes to control Pseudomonas syringae pv. actinidiae

Many research groups, institutions and organizations are involved in discovering the most efficient kiwifruit farming practices for effective control of Pseudomonas syringae pv. actinidiae (Psa). This complicated process requires the analysis and understanding of how environmental factors affect vine susceptibility, which factors favor grow and infection of Psa and, overall, how to implement the most effective practices in protecting against Psa. Several reports have pointed out that there are not curative treatments, but only preventive measures, against Psa. Among these treatments, antibiotics, disinfectants and bactericides have been employed. In this work, we applied six commercial products with copper (Nordox^® and Cobre-Lux^®), zinc (Biobacter^®), aluminum (Fosetil-Al^®) and silver and manganese (Yeti-R^® and Yeti‑F^®, respectively). In addition, two copper(I) complexes synthesized in our laboratory and commercial copper(II) chloride were tested for their efficacy to control Psa from Italy. Among the commercial products tested, only Biobacter^® and Fosetil-Al^® showed in-vitro bactericidal activity, completely inhibiting the growth of all Psa strains isolated and identified from kiwifruit plants of Galicia (Spain). Interesting, the two new copper(I) complexes were very efficient, completely inhibiting bacterial growth of a strain isolated in Italy, used as a control.