Effect of Two Biological Formulations Based onBacillus subtilisandPseudomonas fluorescenson Control ofDidymella applanata, the Causal Agent of Red Raspberry Cane Spur Blight

Abstract

In vitroandin vivostudies were conducted to estimate the efficacy of the two microbial formulations based onBacillus subtilisCohn. andPseudomonas fluorescensMig. on the fungusDidymella applanata(Niessl.) Sacc., the causal agent of red raspberry (Rubus idaeusL.) spur blight.In vitro, both bacteria reduced the growth ofD. applanata. In inoculation experiments with raspberry canes in two cultivars with different susceptibility toD. applanata, these antagonistic bacteria suppressed fungal development by reducing the lesions area and the number ofD. applanatafruiting bodies. Field trials of two biological formulations under natural conditions showed a significant suppression of the disease.B. subtilisandP. fluorescensincluded in the formulations revealed antagonistic activity towardsD. applanatathat depended on the red raspberry cultivar and weather conditions. In all cases,B. subtilisshowed better results thanP. fluorescensin biocontrol of the raspberry spur blight. This study demonstrated for the first time the ability of the biocontrol agentsB. subtilisandP. fluorescensto suppress red raspberry cane spur blight, a serious worldwide disease.