Xylella fastidiosa, a new phytosanitary threat for olive crops

Xylella fastidiosa Wells et al. 1987 (family Xanthomonadaceae) is a Gram-negative, non-motile, non-sporing bacterium endowed with a very peculiar biological and epidemiological behaviour: it colonizes the xylem vessels of the hosts and is transmitted from plant to plant by xylem fluid-feeding insects (leafhoppers of the family Cicadellidae). Because of its polyphagy, when X. fastidiosa enters a new environment with congenial climatic conditions, it becomes rapidly entrenched in the territory. This is what has presumably taken place in Salento, an area where, a few years ago, a destructive disease of olive (Olea europaea L.) developed, denoted olive quick decline syndrome (OQDS), together with a leaf scorch condition of oleander, cherry and almond. Information stemming from studies carried out by the Bari team has laid the basis for implementing a strategy for OQDS containment, based on: (i) accurate surveillance of the territory north of the infected area; (ii) elimination of inoculum sources in newly developed infection foci through the uprooting of infected hosts and the surrounding healthy plants; and (iii) control of vectors by mechanical weeding in late winter/spring to kill juvenile forms, followed by insecticide treatments against the adults when, in late spring, they move from weeds to olives.