Pleurostomophora richardsiae, Neofusicoccum parvum and Phaeoacremonium aleophilum associated with a decline of olives in southern Italy

Abstract

In a recent survey of olive groves in the Canosa di Puglia, Cerignola and Foggia areas of southern Italy a decline of olive trees was observed. The symptoms consisted of a generalised decline of the trees beginning with foliar discolouration and leaf drop, wilting of apical shoots, die-back of twigs and branches, and brown streaking under the bark of the trunk, branches and twigs. At later stages of the disease necrosis and cankers were observed on the bark. The symptoms were similar to those caused by Verticillium wilt, but morphological and molecular analyses demonstrated that the fungal agent responsible was Pleurostomophora richardsiae. Pathogenicity tests carried out on young shoots showed rapid infection by P. richardsiae following artificial inoculation. To our knowledge, this is the first report of P. richardsiae as the causal agent of brown streaking under the bark of olive trees, and of wilt of twigs and leaves. It is not clear if this fungus moves through the phloem or xylem, but on the basis of the sub-cortical symptoms, it appears that it moves through the phloem.