The spread of Xylella fastidiosa depends almost exclusively on insect transmission. So far, in European regions, the principal vector of infection is the meadow spittlebug Philaenus spumarius. It is vital, thus, to keep this insect’s population under control. Scientists are trying to identify P. spumarius natural enemies and assess their efficacy. Although the importance of parasitoids in biological control of pest insects is unquestionable, the scientific literature on the parasitoids of the meadow spittlebug is very scarce.
This work aims at assessing the presence and abundance of a parasitoid fly, Verrallia aucta, in field-collected spittlebugs – namely P. spumarius and Neophilaenus campestris – and its life cycle on the host. Neophilaenus campestris is known as an alternative, although poorly efficient, vector of X. fastidiosa ST53 in Apulia.
The authors developed a new species-specific molecular tool (PCR) to identify the parasitoid. This method allows to detect even very early stages (eggs and first instar larvae) of the developing fly. Then, they estimated the parasitization rate in different sites of northern Italy using both PCR and the dissection of insect bodies. Finally, they established a small-scale rearing to describe the fly’s life cycle on its spittlebug host.
Results showed that V. aucta is quite common in northern Italy, even though with low prevalence. Collected data and rearing observations allow the researchers to conclude that V. aucta is univoltine (meaning it reproduces at a rate of one generation per year) and synchronous with P. spumarius. It lays eggs in newly emerged adults, developing as an endoparasitoid through two larval stages during the whole summer, and overwinters as a pupa in the soil. The exploitation of this parasitoid in conservation/inoculation biocontrol programs against the meadow spittlebug is discussed.