Activity of synthetic and natural compounds for phytoplasma control

A sustainable and rational procedure to evaluate the activity of synthetic and natural substances towards phytoplasma agents of important tree diseases was developed with the aim of finding new strategies of control. The method of testing is based on 1) the utilization of Catharanthus roseus plants; 2) the artificial infection of periwinkles with two phytoplasma strains; 3) scion dipping, selected as the most suitable method of applying the substances. A series of natural and synthetic compounds were chosen among a) new agrochemical entries, registered as plant-resistance in-ducers; b) secondary metabolites of fungal and plant origin; c) new and known biologically active substances never tested before for their antiphytoplasmal properties. The activity of this series of compounds on healthy and phytoplasma-infected periwinkles was evaluated on the basis of several parameters: phytotoxicity, evolution of symptoms and microscope observations. The involvement of the third component in the triangular interaction between phytoplasma, plant and compound is discussed.