Research on European stone fruit yellows (ESFY) in Germany

Since 2000, surveys have been conducted in different stone fruit growing regions in southwest Germany to detect European stone fruit yellows (ESFY) disease in Germany. Each year visual inspections for typical symptoms of ESFY have been done on different Prunus species. Branch samples of all trees with typical symptoms as well as randomized samples from trees with doubtful symptoms have been taken in summer and analysed for infection with 'Candidatus Phytoplasma prunorum'. The pathogen could be detected in the regions Rheinland, Rheinhessen, Vorder- and Suepfalz and Baden and was present in all cultivated Prunus species: P. armeniaca, P. persica, P. domestica and P. amygdalus. For apricots, more than 80% of the samples were infected while peach and European plum were less affected. Almost no infection was found in the wild Prunus species P. spinosa and P. cerasifera. Regular psyllid captures on different Prunus species gave high populations of Cacopsylla pruni on P. spinosa and P. cerasifera while only few individuals were collected from cultivated orchards. The natural infection rate of field collected C. pruni was between 2 and 3%. Transmission trials under controlled conditions showed the capability of C. pruni to transmit the phytoplasma to healthy test plants and proved that C. pruni is also a vector of 'Ca. P. prunorum' in Germany.