A survey in carrot reveals a widespread aster yellows infection, and a first case of ‘Candidatus Liberibacter solanacearum’ in Belgium

In an attempt to identify the agent of widespread yellowing and reddening symptoms, as well as the presence of adventitious roots in commercial carrot in Belgium, an extensive survey on the presence of phytoplasmas and ‘Candidatus Liberibacter solanacearum’ was organised in 2015 and 2016. The survey on 29 fields in the regions Flanders and Hainaut revealed a widespread aster yellows phytoplasma (‘Candidatus Phytoplasma asteris’; AY) presence associated to the majority of the symptoms. A second survey, specifically focused on identifying (potential) plant- and leafhopper vectors (Auchenorrhyncha) was set-up in selected carrot fields. This vector survey resulted in identifying Macrosteles sexnotatus as the most likely vector, and several other plant- and leafhoppers (notably Philaenus spumarius and Typhlocyba quercus) potentially playing a role in the spread of AY. During the insect survey, ‘Candidatus Liberibacter solanacearum’ haplotype D, was found in two commercial carrot fields, however its known psyllid vectors were not found.