Response of Philaenus spumarius and Neophilaenus campestris to potential semiochemicals

Before the Xylella fastidiosa outbreak in Europe and the identification of spittlebugs as the main vectors of this xylem-inhabiting bacterium, little was known about this insect group. The need of effective control tools has highlighted the lack of knowledge on several aspects of spittlebugs’ ecology, such as their response to olfactory stimuli and the potential role of different volatile compounds as semiochemicals. Recently, the antennal sensilla fine structure and the response to several volatile organic compounds were investigated in Philaenus spumarius. Although its antennal chemoreceptors are limited, the meadow spittlebug seems to be able to recognize and react to some substances. While the study of P. spumarius chemical ecology is ongoing, for Neophilaenus campestris this topic is still uninvestigated.
In order to evaluate the response of P. spumarius and N. campestris adults to volatile organic compounds, several Y-tube olfactometer bioassays were carried out. Bergamot essential oil, farnesene, nonanal and undecenal were selected through a preliminary electroantennographic examination. In addition to these compounds, insect body extracts obtained from 5 males and five females of both species were tested too. The average linear speed of the insect in the olfactometer and time spent in the two arms (treatment vs. control) were considered. In response to almost all the substances, a decrease in the linear speed for both males and females of N. campestris was evidenced in comparison to pure air. Males of both species responded to farnesene remaining for a longer time in the arm containing the substance compared to the arm with pure air. Moreover, when considering the body extracts of males or females both species showed a linear speed significantly different compared to the control tests. These results may suggest that one or more volatile compounds extracted from spittlebug bodies could play a role as semiochemicals, especially in N. campestris.