Abstract
As a vector of Xylella fastidiosa (Wells, 1987) in Europe, the meadow spittlebug Philaenus spumarius (Linnaeus, 1758) (Hemiptera, Aphrophoridae) is a species of major concern. Therefore, tools and agents to control this ubiquitous insect that develops and feeds on hundreds of plant species are wanted. We conducted a field survey of P. spumarius eggs in Corsica and provide a first report of Ooctonus vulgatus Haliday, 1833 (Hymenoptera, Mymaridae) as a potential biocontrol agent of P. spumarius in Europe. To allow species identification, we summarized the main characters distinguishing O. vulgatus from other European species of Ooctonus and generated COI DNA barcodes. Parasitism rates were variable in the four localities included in the survey but could reach 69% (for an average number of eggs that hatched per locality of 109). Based on the geographic occurrences of O. vulgatus obtained from the literature, we calibrated an ecological niche model to assess its potential distribution in the Holarctic. Obviously, several questions need to be addressed to determine whether O. vulgatus could become an effective biocontrol agent of P. spumarius in Europe. So far, O. vulgatus has been reared only from P. spumarius eggs, but its exact host-range should be evaluated to ensure efficiency and avoid non-target effect. The top-down impact of the parasitoid on vector populations should also be assessed on large data sets. Finally, the feasibility of mass rearing should be tested. We hope this report serves as a starting point to initiate research on this parasitoid wasp to assess whether it could contribute to reduce the spread and impact of X. fastidiosa in Europe.
Highlights
Xylella fastidiosa (Wells, 1987) is a xylem-dwelling insect-borne bacterium, that originates from the Americas and causes a variety of scorch-like diseases in more than 500 species of plants including many cultivated species (Almeida & Nunney 2015; EFSA 2015; EFSA 2018; Sicard et al.2018)
All parasitoids reared from the eggs of P. spumarius were identified as O. vulgatus (Figure 2)
In the Holarctic region, O. vulgatus can be discriminated from other species of Ooctonus by the following unique combination of features (Figure 2): vertex without stemmaticum; mesoscutum without median groove; posterior part of scutellum and frenum smooth with weak sculpture laterally; metanotum and propodeum without reticulate sculpture; propodeum without median carina, but with a pentagonal areole formed by dorsolateral carinae; short petiole, 0.9–1.2x as long as metacoxa; forewing at least slightly truncate apically; females funicle with multiporous placoid sensilla on F7 and F8
Summary
Xylella fastidiosa (Wells, 1987) is a xylem-dwelling insect-borne bacterium, that originates from the Americas and causes a variety of scorch-like diseases in more than 500 species of plants including many cultivated species (Almeida & Nunney 2015; EFSA 2015; EFSA 2018; Sicard et al.2018). Studies on the economic impact of X. fastidiosa are scarce and have primarily focused on the vineyard and wine industry. X. fastidiosa has been recently detected in Europe and is present in Italy (Saponari et al 2013), France (Denancé et al 2017), Spain (Olmo et al 2017) and Portugal (DGAV 2019). X. fastidiosa represents a serious threat to European agriculture and natural ecosystems
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