Studies on the interaction between Ca. Phytoplasma pyri and the vectoring psyllids

Abstract: The quarantine disease Pear Decline (PD) is widespread in Austria and it is a serious problem in high stem as well as in organic pear orchards. The presented data confirmed the occurrence of the three pear psyllid species Cacopsylla pyricola, Cacopsylla pyri, Cacopsylla pyrisuga and the hawthorn psyllid Cacopsylla melanoneura in Austrian pear orchards. The prevalence of the different species is site-specific and influenced by the sampling time. C. pyricola, C. pyri and C. pyrisuga were carrier of ‘Ca. Phytoplasma pyri’ with an average infection rate between 3% and 7%. The summer forms of the psyllids were more often infected than the winter forms. In the present study ‘Ca. P. pyri’ was not ascertained in C. melanoneura. Females of all 3 species were more frequently infected than males, whereby C. pyri females showed the highest infection rate. The obtained results also indicated that the psyllids preferred uninfected pear trees more than infected ones, but further investigations are necessary to verify these findings.