Phytoplasma infection induces changes in vibrational mating behaviour of Cacopsylla pyri: sex-specific shifts in frequency, amplitude, and timing

The pear psyllid ( Cacopsylla pyri ), the main vector of ‘ Candidatus Phytoplasma pyri’, relies on substrate-borne vibrational signals for mate recognition and duet coordination. As pathogens can alter insect communication, we examined whether phytoplasma infection alters key parameters of male and female mating signals. We used laser vibrometry on a standardised artificial substrate, as well as playbacks, to examine this. We detected clear sex-specific effects of infection at the level of individual signals. Infected females produced significantly longer inter-chirp intervals and higher dominant frequencies than uninfected females. In males, infection significantly reduced the amplitude of chirps, whereas uninfected males showed a markedly higher number of interruptions within their trill units. These infection-induced changes likely reflect a physiological burden, such as altered energy allocation or in cuticular stiffness, which affects vibrational mechanics. Despite these clear differences at the individual level, however, duet communication between males and females did not differ significantly between infection treatments. This suggests that basic mating communication is preserved, indicating that it probably has no negative impact on mating success. However, we recommend focusing on mating success in future studies to determine whether the duets on a natural substrate remain also unaffected.