A systematic large-scale vector monitoring programme to optimise strategies for controlling vectors of Xylella fastidiosa

Transmission tests carried out in Apulia region (southern Italy) identified three spittlebug species as vector of Xylella fastidiosa (Xf) subspecies pauca, ST53, causing severe decline on olive trees. This information, along with the data on the host-preference and biology, has been essential to assist the implementation of the containment measures in place, in the so called Xylella-demarcated areas, where actions for the control of the vector are mandatory. Since 2019, the Apulian Phytosanitary Authority is supporting a monitoring programme to promote a sustainable and effective application of the vector control strategies (mechanical interventions for reducing the juveniles and applications of insecticides for the adults). The programme aims to provide accurate estimation of the best time to apply the specific interventions, i.e. in relation to the stage of development (juveniles) and to the population dynamics (adults) in olive groves and other crops. A total of 40 representative locations (located at different altitudes) were selected, in the Xf-free area, through the buffer, containment and infected areas. These include cultivated (plots under organic and IPM management) and non-cultivated sites, monitored periodically from March to October. Surveys for juveniles are based on a standard number of field sampling units (transect), whereas the counting of adults is made through traps and a fixed number of sweeping net/canopy/plot. A weekly/biweekly bulletin is then published by the Phytosanitary Authority with recommendations/specific warnings on the most appropriate timing for applying the mandatory control measures. The data so far collected confirmed that the length of the juvenile stages is greatly influenced by the micro-climatic conditions, and as such, the timing for mechanical interventions on the ground vegetation has to be targeted area-by-area. Ultimately, important information is going to be collected regarding the population density, which in the future will help to target the areas/crops/ecosystems where vector control should be prioritised.