Sustainable products to control the strawberry angular leafspot

Within the scope of the EU Regulation proposal on the sustainable use of pesticides to reduce dependence on chemicals until reaching Zero-tolerance by 2030, reliable and convenient alternatives to control the plant bacteriosis are investigated. Unfortunately, sustainable biocontrol agents are not always available or their economic impact on crop production is penalizing compared to the conventional products (e.g. heavy metals and antibiotics). In this study, the essential oils-based product Microsap® BIO 458 (458), the foliar fertilizer Probaction® and the resistance inducer Bion® (unregistered on strawberry) were tested in vitro against Xanthomonas fragariae (Xf, DISTAL 12191 strain), the causal agent of strawberry angular leafspot (ALS). Two experiments on young strawberry plants were carried out under controlled conditions by using 458 at 0.15% and 1%, Probaction® at 0.4% and Bion® treated once at 150 ppm and twice at 100 ppm against ALS. In vitro, all the tested products, except Bion®, resulted bactericidal. In vivo, all products reduced the ALS severity on strawberry plants, in particular, 458 at 0.15% and 1% gave a relative protection (RP) of about 40% and 34%, respectively; Probaction® gave 67% RP, while Bion® treated once and twice provided approx. 38% and 74% RP, respectively. Streptomycin sulphate (100 ppm) used as positive control gave RP of about 65% in the first experiment and of 44% in the second. All tested products showed their ability in reducing ALS severity and thus they offer a valid alternative to chemicals in the disease management to reduce the inoculum sources.