Effect of Two Biological Formulations Based on<i>Bacillus subtilis</i>and<i>Pseudomonas fluorescens</i>on Control of<i>Didymella applanata</i>, the Causal Agent of Red Raspberry Cane Spur Blight

In vitro and in vivo studies were conducted to estimate the efficacy of the two microbial formulations based on Bacillus subtilis Cohn. and Pseudomonas fluorescens Mig. on the fungus Didymella applanata (Niessl.) Sacc., the causal agent of red raspberry ( Rubus idaeus L.) spur blight. In vitro , both bacteria reduced the growth of D. applanata . In inoculation experiments with raspberry canes in two cultivars with different susceptibility to D. applanata , these antagonistic bacteria suppressed fungal development by reducing the lesions area and the number of D. applanata fruiting bodies. Field trials of two biological formulations under natural conditions showed a significant suppression of the disease. B. subtilis and P. fluorescens included in the formulations revealed antagonistic activity towards D. applanata that depended on the red raspberry cultivar and weather conditions. In all cases, B. subtilis showed better results than P. fluorescens in biocontrol of the raspberry spur blight. This study demonstrated for the first time the ability of the biocontrol agents B. subtilis and P. fluorescens to suppress red raspberry cane spur blight, a serious worldwide disease.