# More than Just Host Plant Preferences for the Two Main Vectors of Xylella fastidiosa in Europe: Two Insect Species and Two Different Behaviors

## TL;DR

This study shows that two insect vectors of Xylella fastidiosa in Europe have different plant preferences and behaviors, which can inform strategies to control the spread of the disease.

## Contribution

The study reveals distinct oviposition and nymphal development behaviors of two Xylella vectors under semi-field conditions.

## Key findings

- Neophilaenus campestris prefers grass for egg-laying and nymph development.
- Philaenus spumarius lays eggs on dry soil and favors single-host environments for higher oviposition rates.
- Nymphs of both species survive best on their preferred host plants.

## Abstract

Xylella fastidiosa is a plant disease-causing bacterium that has devastating impacts on global agriculture, affecting crops such as olives, grapes, and citrus. In Europe, two main insect species are responsible for transmitting the disease: the spittle bugs Neophilaenus campestris and Philaenus spumarius. Understanding how these insects interact with plants is essential to limiting the spread of the disease. In this work, we studied how plant species and habitat diversity influence the oviposition behavior of adult females and the development of nymphs in both species. Neophilaenus campestris showed a strong preference for grass plants for both egg-laying and nymph development, while P. spumarius primarily laid its eggs on dry soil substrates, regardless of the host plant species. Interestingly, P. spumarius females had increased oviposition rates when only a single preferential host was present. These findings underscore the importance of managing agricultural landscapes to disrupt the interactions between host plants and vectors, thereby reducing the spread of X. fastidiosa.

Xylella fastidiosa is a vector-borne bacterium causing significant economic losses in global agricultural industries. Management strategies focus primarily on controlling vector populations. The diversity of vector species, their polyphagy, and the wide range of host plants supporting bacterial development make X. fastidiosa pathosystems particularly challenging to manage. Understanding vector and host plant relationships is key to developing effective strategies. This study examined the oviposition strategies, host preferences, and nymphal development of Europe’s main X. fastidiosa vectors, Philaenus spumarius and Neophilaenus campestris, under semi-field conditions (screenhouse). The two species exhibited distinct behaviors. Neophilaenus campestris primarily laid eggs on its preferential host, the grass Festuca arundinacea, while P. spumarius preferred dry soil substrates, irrespective of the host plant species. The presence of multiple hosts reduced the oviposition rates of P. spumarius compared with single-host scenarios. The nymphs of P. spumarius quickly identified and settled on preferential hosts, while the N. campestris nymphs initially moved randomly but later congregated on their preferred host. Despite their polyphagy, nymph survival was limited to preferential hosts. These findings highlight opportunities for habitat management strategies, such as enhancing plant diversity and eliminating overwintering egg sites, to mitigate vector populations and limit the spread of X. fastidiosa.