Abstract
We sampled ca 2500 specimens of Philaenus spumarius (Hemiptera: Aphrophoridae) throughout Corsica without a priori knowledge on the presence of symptoms on plants. We screened 448 specimens for the presence of Xylella fastidiosa (Xf) using qPCR and a custom nested PCR. qPCR appeared versatile and under-estimated the prevalence of Xf. Nested PCR showed that Xf was present in all populations. Molecular results were validated by prediction on the distribution of Xf made from tests conducted on plants, which shows the pertinence of using vectors in risk assessment studies. Xf was detected in tenerals and adults. Thus, P. spumarius could acquire Xf from its host plant, mostly Cistus monspeliensis in Corsica, which may act as reservoir for the next season. This contrasts with other observations and suggests that management strategies may have to be adapted on a case-by-case basis. At least two genetic entities and several variants of Xf not yet identified on plants were present in the insects, which suggests ancient introductions of Xf and a probable underestimation of the current diversity of the strains present in Corsica. Interestingly 6% of the specimens carried two subspecies of Xf. Studies are required to better characterize the strains present in Corsica and to determine how the disease was introduced, spread and why no sign of a potential epidemic was detected earlier. This study shows that, when sensitive enough methods are implemented, spittlebugs (and more specifically P. spumarius for which species distribution modelling shows it could be a good sentinel for Europe) can be used to predict and better assess the exact distribution of Xf. Furthermore, Xf multiply only in their foregut and does not become circulative, which facilitates its detection.
Highlights
In the last few years several subspecies of Xylella fastidiosa (Xf) have been detected in Europe
Xf multiplex was detected in eastern parts of the Iberian peninsula and Xf multiplex, Xf pauca and Xf fastidiosa were detected in the Balearic Islands[12]
We propose to make a large-scale preliminary identification of the subspecies/strains of Xf that may be present in the ecosystem
Summary
In the last few years several subspecies of Xf have been detected in Europe (https://gd.eppo.int/taxon/ XYLEFA/distribution, https://ec.europa.eu/food/plant/plant_health_biosecurity/legislation/emergency_measures/xylella-fastidiosa/latest-developments_en). As suggested by the “spy insect” approach set up in buffer zones and symptom-less areas closed to contaminated olive groves in Italy[34,35,36], implementing massive surveys to test whether or not insect populations in different ecosystems do carry Xf would efficiently complement studies on plants and improve the early detection and monitoring of the disease. We propose to test the feasibility of a large screening of insect populations for the presence of Xf and for the possible characterisation of the carried strains via PCR amplification and sequencing of the loci included in the MLST of Xf. We sampled 62 populations of Philaenus spumarius throughout Corsica (Fig. 1, Table S1) from early June (when there was still a mix of larvae and adults, Fig. S1) to late October (before the adults are presumably killed by winter). We collected occurrence data of P. spumarius throughout Europe and estimated its geographical range using species distribution modelling to discuss the interest of using this insect species as a sentinel for the early detection and monitoring of Xf in Europe
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
