FUNGAL SPECIES ASSOCIATED WITH A SEVERE DECLINE OF OLIVE IN SOUTHERN ITALY

Abstract

A severe olive decline of unknown aetiology is currently under investigation in Apulia, (southern Italy). The decline affects mainly aged trees (100 years or older) growing in the Gallipoli bay, on an area extending about 10.000 ha located on the western coast of the Salento peninsula. The disease is characterized by a rapid dieback of shoots, twigs and branches followed by death of the entire tree. Leaf tips and margins turn dark yellow to brown, a condition that spreads inward, eventually leading to desiccation. Symptoms progress in severity from older to younger leaves. Desiccated leaves and mummified drupes remain attached to the shoots. Trunks, branches and twigs viewed in cross section show more or less extensive discolorations of the vascular elements, as reported earlier by Carlucci et al. (2008), plus sapwood and vascular cambium. Numerous galleries of the leopard moth, Zeuzera pyrina and bark beetles occurr on the trunks, branches and twigs of affected plants. Isolations from discolored sapwood made on different growing media allowed the recovery of a number of fungi, Phaeoacremonium spp. in particular, which were identified based on morphometric characters and sequencing of ITS and β-tubulin gene regions (Mostert et al., 2006). P. parasiticum was the most frequent species, followed by P. rubrigenun, P. aleophilum, P. alvesi,. Fungi belonging to the genus Phaemoniella were also found. This is the first report of P. parasiticum and P. alvesii on olive in Italy. The role of these fungal species, alone or in combination with other plant pathogens, in determining the symptoms observed on olive trees is currently under investigation.