Strategies for reducing vector populations and transmission of Xylella fastidiosa in olive groves

Much of the work regarding insecticidal efficacy against Philaenus spumarius has been initiated only in the past few years, when the control of this spittlebug species in the area where outbreaks of Xylella fastidiosa emerged, became essential. Among the numerous formulations (synthetic and organic insecticides) tested to control the adults on olives, a major affected European crop, neonicotinoids and pyrethoids showed the highest efficacy and persistence (Dongiovanni et al., 2018). These trials were extended in 2018 and 2019 by testing a new formulate based on acetamiprid and one based on cyantraniliprole, a systemic insecticide belonging to anthranilic diamide. For both, results showed high efficacy against P. spumarius indicating they could be adopted for controlling spittlebug populations in the framework of the application of containment measures for X. fastidiosa.<br> Whereas, with the purpose of reducing the efficiency of X. fastidiosa vector transmission under organic farming management, applications of kaolin were tested for four consecutive years as a preventive approach to protect a new olive plantation exposed to the natural inoculum pressure. Although, applied on a calendar basis, the use of kaolin did not protect the young olives from infections and subsequent symptoms development. Surprisingly, this was also the case of the plants treated with the insecticide used as control, based on imidachloprid, for which, even if to a lower extent, infections also occurred.<br> Attempts were also made to implement strategies, alternative to the mechanical control of weeds, for controlling the juveniles, a stage of the insect life when they are more vulnerable and control can be more efficient. Sowing different gramineous species to replace the natural ground vegetation, applications of herbicides and pyroherbicides, were compared. Soil tillage, pyroherbicides and herbicides applied in spring were the only interventions able to reduce almost to zero the presence of juvenile spittlebugs.<br> The experimental data herein developed will be helpful for the end-users to choose better options for the management of this vector in different agroecosystems.