Management of Botryosphaeria dieback in Australian walnut orchards

Dead branches, dried fruiting spurs, necrotic lesions on current season’s growth, and black fruits with shrivelled kernels are widespread in walnut orchards in Australia, resulting in significant yield loss. Fungal species belonging to the family Botryosphaeriaceae have been reported as the causative agents in similar diebacks in other crops in Australia, and in walnuts in other countries. The disease, referred to as Botryosphaeria dieback, has been implicated in economic loss in many horticultural crops of economic importance including nut crops such as almond, macadamia, and pistachio. Against this background, this research identified the species of Botryosphaeriaceae present in walnut orchards in Australia and investigated their pathogenicity and methods of control.