Xylella fastidiosa subspecies and sequence types detected in Philaenus spumarius and in infected plants in France share the same locations

Abstract

In Europe, the meadow spittlebug Philaenus spumarius is the main known vector of the quarantine bacterium Xylella fastidiosa. So far detection and identification of X. fastidiosa has more often been performed from plant matrices than insects, mainly using a real‐time PCR and multilocus sequence typing (MLST) approach. Detection of X. fastidiosa in its insect vectors would enhance knowledge of the epidemiologic situation in France, specifically in the already infected Corsica and Provence‐Alpes‐Côte d’Azur (PACA) regions. The aim of this study was to validate a methodological approach to detect X. fastidiosa in P. spumarius, analysed individually or in groups of 10, using real‐time PCR and MLST, and to apply the approach to more than 4,000 individuals collected between 2015 and 2019 from infected areas. The corresponding results expanded our knowledge of the epidemiology of X. fastidiosa in France: (a) X. fastidiosa subsp. multiplex including the sequence types ST6 and ST7 were identified in the insect vector; (b) the rate of positive insects per infected area was as high as 33.3% in Corsica or 50% in the PACA region; (c) positive adults were found during winter; and (d) the bacterial load in P. spumarius (droplet digital PCR) usually ranged from 103 to 104 cells per insect, but could be as high as 105 or 106 cells per insect for some individuals (13%). The subspecies and sequence types detected in P. spumarius corresponded to the situation officially reported for plants in the same areas.

Climate tolerances of Philaenus spumarius should be considered in risk assessment of disease outbreaks related to Xylella fastidiosa

“…The meadow spittlebug is a univoltine species overwintering as eggs; eggs hatch in late winter or early spring and nymphal instars develop producing characteristic foams that presumably act as a thermoregulation and defensive strategy (Weaver and King 1954;Tonelli et al 2018). Adults usually appear in spring and live until late summer or fall, even though few adults of P. spumarius were occasionally sampled in late winter in France and Italy (Bodino et al 2019;Cunty et al 2020). In Mediterranean regions characterized by high precipitation seasonality, adults usually spend spring feeding on herbaceous vegetation and migrate to woody hosts-including a large range of trees, shrubs and agricultural crops-in late spring or early-summer concomitantly to rainfall decreases when herbaceous vegetation dries out (Cornara et al 2018;Cruaud et al 2018;Morente et al 2018;Antonatos et al 2019;Bodino et al 2020).…”

Diseases Caused by Xylella fastidiosa in Prunus Genus: An Overview of the Research on an Increasingly Widespread Pathogen

“…In France, P. spumariusis is considered the main vector for both diseases in Corsica; and in the region of PACA, captured specimens showed both strain types (ST6 and ST7) of subsp. multiplex present in these regions (Cunty et al, 2020).…”

Aphrophoridae Role in Xylella fastidiosa subsp. pauca ST53 Invasion in Southern Italy

“…Based on the impact of an insect-borne pathogen [ 183 , 184 ] vector control is the only available approach. The infectious efficiency of spittlebug vectors, the high percentage of virulent adults [ 185 ], and their mobility [ 36 ] concerning the rapid induced decline of olive suggest that Xylella -vectors should be considered the new key-pest of olive trees [ 186 ].…”

“…The juvenile-vector population size knowledge is crucial in establishing an effective control strategy whereby choosing action thresholds, tuning control action intensity, and estimating control efficacy [ 73 ]. The first experience on spittle quantitative sampling, by direct in-field scrutiny, revealed an expensive approach in time and workforce [ 185 ]. Moreover, the population size gathered data are not congruous among pre-imaginal instar.…”