FIRST REPORT OF STEMPHYLIUM sp. ON OLIVE TREES IN SICILY.

Abstract

In the last five years, we have observed a new decline of Olea europaea in north-western and southern Sicily (insular Italy). The syndrome consists in more or less extensive leaf chlorosis, sometimes with irregular necrotic marginal or apical spots. Apical defoliation of twigs showing cortical necrosis and withering has often been observed. Isolations, carried out in 2007/08, yilded a complex of fungal genera associated with the syndrome. Among these, Stemphylium sp., a well-known foliar pathogen of other plants, was constantly isolated from all the alterations observed. In December 2010, single spore colonies of this fungus were used for artificial inoculations on healthy 3-year-old olive plants (cv. Biancolilla). Necrotic foliar spots, extending from the inoculum site to the apex leaf, and twig cortical necrosis with darkening of internal tissues were, observed from 15/40 and 90/120 days, respectively, after inoculations. Colonies of Stemphylium sp. were always re-isolated from all symptomatic organs, thus fulfilling Koch’s postulates. To our knowledge, this is the first report of Stemphylium sp. as a pathogen to olive trees in Sicily. Further morphological and molecular studies are in progress to achieve specific identification.