Behaviour response of Philaenus spumarius, the main vector of Xylella fastidiosa, to traditional Portuguese olive cultivars

Abstract: In Portugal, Xylella fastidosa, a gram-negative phytopathogenic bacterium, has been detected in 2019 in the North of the country in urban areas, raising concerns with the possibility of this bacterium spread up to crops of economic importance such as the olive grove. This bacterium is transmitted by the xylem sap feeder Philaenus spumarius (Linnaeus, 1758). Understanding the olfactory response of P. spumarius to traditional olive cultivars of Portugal is essential to determining the most attractive olive cultivar to this vector. This could help to implement proper prevention and control measures against the spread of X. fastidiosa throughout Portuguese olive groves. The goal of this work was to evaluate the olfactory response of females and males of P. spumarius to five traditional Portuguese olive cultivars (Cvs. “Cobrançosa”, “Negrinha de Freixo”, “Santulhana”, “Madural” and “Verdeal Transmontana”). The olfactory response to the cultivars was assessed by two trials on an eight-chamber olfactometer. In the first trial, the behaviour of 16 individuals towards the cultivars “Verdeal Transmontana”, “Cobrançosa” and “Madural” was recorded. The second assay was used to assess the behavior of 16 individuals towards the most chosen cultivar in the first trial (“Cobrançosa”) and the cultivars “Negrinha de Feixo” and “Santulhada”. The insects were allowed to make their choice during 30 minutes for each trial. For each trial and sex, 20 repetitions were made. A stream of purified air was used as control. In the first trial, females and males were significantly more attracted by “Cobrançosa” (P < 0.001). “Negrinha de Feixo” was the cultivar significantly most chosen in the second trial (P < 0.001). No significant differences were observed between males and females (P = 0.38). On average, two out of 16 individuals did not make any choice. Our results suggest that the “Negrinha de Feixo” could be the most attractive cultivar to the main vector of X. fastidiosa. However, assays of feeding preference and studies of presence and abundance of P. spumarius in olive groves must be conducted to confirm our results.