First detection of apple proliferation and pear decline phytoplasmas in Luxembourg

The present article reports the first detection of the apple proliferation and pear decline phytoplasmas (‘Candidatus Phytoplasma mali’ and ‘Ca. P. pyri’, respectively) in Luxembourg. These phytoplasmas, belonging to the 'Apple Proliferation group' 16SrX, are causing severe losses in European fruit tree production, respectively, on apple (Malus domestica) and pear (Pyrus communis), and they are on the EPPO A2 List of pests recommended for regulation as quarantine pests. The main insect vectors of these phytoplasmas belong to the superfamily Psylloidea, also known as psyllids or jumping plant lice (Insecta: Hemiptera). No data was available for Luxembourg concerning the distribution of phytoplasma infections, while many of their psyllid vectors were recently detected in a countrywide assessment. The present work reports the results of a survey of both psyllids and their vectored phytoplasmas on apple, plum, pear, cherry, blackthorn and common hawthorn. Among the collected samples, plant samples from Malus spp. trees and insect samples of Cacopsylla picta—both from orchards—tested positive for apple proliferation phytoplasma, while only plant samples from Pyrus spp. trees in orchards tested positive for pear decline phytoplasma. The implications of these findings within Luxembourg and the Greater Region are discussed.