Efficacy of Biological Control Agents and Resistance Inducer for Control of Mal Secco Disease

Mal secco, caused by is an economically important fungal vascular disease in citrus-growing countries of the Mediterranean basin. Preventing fungal infections usually requires a high number of copper treatments but European legislation imposes the minimization of their accumulation in soil. In our study, biological control agents (BCAs) and a plant resistance inducer (PRI), tested in four different experiments on citrus seedlings under controlled conditions, have resulted in promising strategies to control mal secco disease. Foliar (Experiment I) and soil (Experiment II) applications of two formulations of strain D747 (Amylo-X LC and Amylo-X WG) provided similar performances in reducing the disease amount (incidence and symptoms severity) over time compared to the untreated control, whereas copper hydroxide (Kocide Opti ) used as standard was the most effective treatment over time. In the third experiment, strain M1 (Polyversum ) and strain ICC012 strain ICC080 (Remedier ) were able to reduce disease incidence and symptoms severity compared to the untreated control. Remedier provided the best performances in reducing the disease amount, whereas the Polyversum application was the least effective treatment over time. The effectiveness of the spp. formulation in reducing infections did not significantly differ from the standard copper compound (Kocide Opti ). Comprehensively, in the last experiment (IV), acibenzolar-S-methyl (ASM) alone and in mixture with metalaxyl-M proved as effective as strain FZB24, with no dose-response relationships observed. These findings provide important insight for the integrated management of mal secco disease.