Antagonistic effect in vitro of three commercial strains of Bacillus sp. against the forest pathogen Diplodia corticola

Botryosphaeria canker of Quercus suber (causal agent: Diplodia corticola) poses a major threat for cork production along the western Mediterranean Basin. Infection by D. corticola induces cankers, which reduce tree vigour and compromise phellem regeneration. European policies in forest health advise the use of environmentally friendly methods, such as biocontrol, rather than the use of chemicals in natural stands. In this study, we assessed the antagonistic potential of three commercial products involving bacteria (Bacillus amyloliquefaciens and Bacillus mojavensis) using two culture media [potato-dextrose-agar medium (PDA), and PDA amended with copper oxychloride, an inorganic fungicide] against D. corticola. Five indices based on colony dimensions showed significant antagonistic effects of bacteria on fungal growth in vitro. The copper salt showed high toxicity against D. corticola. Preliminary results suggest that the three commercial products might be used as biocontrol agents against D. corticola, whose control capacities in the field deserve further investigation.