A biological control model to manage the vector and the infection of Xylella fastidiosa on olive trees

Abstract

Xylella fastidiosa pauca ST53 is the bacterium responsible for the Olive Quick Decline Syndrome that has killed millions of olive trees in Southern Italy. A recent work demonstrates that a rational integration of vector and transmission control measures, into a strategy based on chemical and physical control means, can manage Xylella fastidiosa invasion and impact below an acceptable economic threshold. In the present study, we propose a biological alternative to the chemical control action, which involves the predetermined use of an available natural enemy of Philaenus spumarius, i.e., Zelus renardii, for adult vector population and infection biocontrol. The paper combines two different approaches: a laboratory experiment to test the predation dynamics of Zelus renardii on Philaenus spumarius and its attitude as candidate for an inundation strategy; a simulated experiment of inundation, to preliminary test the efficacy of such strategy, before eventually proceeding to an in-field experimentation. With this double-fold approach we show that an inundation strategy with Zelus renardii has the potential to furnish an efficient and "green" solution to Xylella fastidiosa invasion, with a reduction of the pathogen incidence below 10%. The biocontrol model presented here could be promising for containing the impact and spread of Xylella fastidiosa, after an in-field validation of the inundation technique. Saving the fruit orchard, the production and the industry in susceptible areas could thus become an attainable goal, within comfortable parameters for sustainability, environmental safety, and effective plant health protection in organic orchard management.

Xylella fastidiosa in Olive: A Review of Control Attempts and Current Management

“…More recently, the occurrence of the egg parasitoid Ooctonus vulgatus Haliday was reported in Corsica [ 95 ]. The predation dynamics of the generalist predator Zelus renardii Kolenati on P. spumarius were reported by Liccardo et al [ 96 ]. Furthermore, Molinatto et al [ 97 ] reported the infestation of field-collected spittlebugs by the parasitoid fly Verrallia aucta Fallén.…”

Biology and Prevalence in Northern Italy of Verrallia aucta (Diptera, Pipunculidae), a Parasitoid of Philaenus spumarius (Hemiptera, Aphrophoridae), the Main Vector of Xylella fastidiosa in Europe

“…Following the discovery of X. fastidiosa in Europe, namely of the subsp. pauca transmitted to olive by P. spumarius, interest in biological control agents of this pest has greatly increased and has prompted research on natural enemies, namely an egg parasitoid, O. vulgatus [20] and a generalist predator, Z. renardii [21]. Verrallia aucta does not rapidly kill the host, which can survive until late in the season.…”

“…Interestingly, very recently, one of the oophagous parasitoids recorded from US, Ooctonus vulgatus Haliday, has been found commonly and locally abundant in Corsica island of France [20]. Finally, the newly introduced predatory bug Zelus renardii Kolenati (Hemiptera, Reduviidae) has been proposed for the inundative control of P. spumarius with the aim of suppressing the spread of X. fastidiosa in olive groves of Apulia [21]. However, the mass release of such a generalist predator may be risky for local biodiversity, especially for beneficial arthropods [22], while its efficacy under field conditions has yet to be demonstrated.…”

Screening of Olive Biodiversity Defines Genotypes Potentially Resistant to Xylella fastidiosa

“…Xf can be limited by agronomic practices affecting the vector Philaenus spumarius (Liccardo et al, 2020;Schneider et al, 2020) and, possibly, by acting on the soil microbiome (Fernández-González et al, 2019). However, replanting with resistant genotypes appears as the most feasible and promising strategy to control the bacterium.…”