Vector transmission and epidemiology of ‘Candidatus Phytoplasma pyri’ in Austria and identification of Cacopsylla pyrisuga as new pathogen vector

Abstract

Pear decline, induced by the phytoplasma 'Candidatus Phytoplasma pyri', transmitted by pear psyllids, is one of the most devastating diseases on Pyrus communis in Europe and North America. Investigations of pear psyllids in 4 pear orchards in lower Austria showed the presence of Cacopsylla pyri, C. pyricola and C. pyrisuga at all locations. PCR analyses revealed overall phytoplasma infection rates for C. pyri of 5.4%, for C. pyricola, of 4.6%, for C. pyrisuga remigrants of 9.6% and for C. pyrisuga emigrants of 0%. The rates of PCR-positive C. pyri and C. pyricola individuals varied greatly in the course of the year, and the highest infection rates were observed in late summer, autumn and in late winter. In transmission experiments with healthy pear seedlings, winterform individuals of C. pyri and C. pyricola transmitted the pathogen to 19.2% (5 out of 26) and 4.8% (2 out of 41) of the test plants, respectively. The vectoring ability of C. pyrisuga was experimentally proven for the first time, and in transmission experiments with remigrants, 9.5% (2 out of 21) of the pear seedlings were infected. Our data indicate a significant risk of pathogen transmission in pear orchards during the greater part of the year, especially in late winter, early spring and autumn. Multilocus sequence analysis by aid of the genes aceF and imp allowed the discrimination between 15 phytoplasma types. Three so far undescribed aceF genotypes and four undescribed imp genotypes were identified.

The importance of assessing the population structure and biology of psylla species for pest monitoring and management in pear orchards

“…These psylla species are also vectors of some typical pear tree pathogens (Moreno et al, 2021) such as the bacterium Erwinia amylovora Burrill, which causes fire blight (Hildebrand et al, 2000), one of the most devastating pear diseases (Sestras et al, 2008). It has also been confirmed that the pear psyllid is the vector transmitting the phytoplasma known as 'Candidatus Phytoplasma pyri' that causes a serious disease known as 'pear decline' (Tešanović et al, 2016;Riedle-Bauer et al, 2022).…”

First systematic inventory of the jumping plant lice of Luxembourg (Hemiptera, Sternorrhyncha, Psylloidea)

“…However, it has been recently confirmed as a vector of " Ca. Phytoplasma pyri ", the causing agent of Pear Decline ( Riedle-Bauer et al 2022 ).…”

Microbiome of pear psyllids: A tale about closely related species sharing their endosymbionts

“…C. pyrisuga had not been considered a competent vector of ‘ Ca . Phytoplasma mali’ (Jarausch et al, 2019 ; Jarausch & Jarausch, 2010 ), until Riedle‐Bauer et al ( 2022 ) recently demonstrated experimentally that remigrants of C. pyrisuga are able to transmit ‘ Ca . Phytoplasma mali’ to pear trees in Austria.…”

“…Both vectors produce up to 3–5 generations per year and show resistance to insecticides, making it difficult to control population outbreaks (Civolani, 2012 ). In contrast to C. pyri and C. pyricola , C. pyrisuga had been considered a non‐vector species until recently, when its vector competence was experimentally proven in Austria (Riedle‐Bauer et al, 2022 ). However, it is not known to what extent this species acts as a vector in other parts of Europe.…”