‘Candidatus Liberibacter solanacearum’ is associated with decline of ash trees in Canada
In North and Central America, 'Candidatus Liberibacter solanacearum' (Solanaceae haplotypes are listed in the EPPO A1 List) is associated with psyllids of the genus Bactericera including Bactericera cockerelli (Hemiptera: Triozidae - EPPO A1 List), and causes diseases on Solanaceae plants.
Over the past 20 years ash trees (Fraxinus nigra and F. mandshurica) in parts of the western USA (Montana, South Dakota, and North Dakota) and Canada (Alberta, Manitoba, Saskatchewan) showed a decline including pseudogalls, canopy loss and eventually tree death. The decline was associated with infestation by the psyllid Psyllopsis discrepans (Hemiptera: Psyllidae), a species originating in Europe and introduced in North America in the 1900s. Before 2000, infestations of Fraxinus trees by P. discrepans did not result in tree deaths. Recent analysis detected ‘Ca. Liberibacter solanacearum' in P. discrepans collected from ash trees in Saskatchewan, and suggested that this pathogen may be causing the recent ash decline. It is hypothesized that P. discrepans may have acquired ‘Ca. Liberibacter solanacearum' while feeding on the same host plant as Bactericera maculipennis.
Sources
Boone J, Wist TJ, Prager SM (2022) Evaluating acephate and azadirachtin for control of Psyllopsis discrepans (Flor) (Hemiptera: Psyllidae) and prevention of decline of ash trees. The Canadian Entomologist 154(1), e13. https://doi.org/10.4039/tce.2021.61
Wamonje FO, Zhou N, Bamrah R, Wist T, Prager SM (2022) Detection and identification of a ‘Candidatus Liberibacter solanacearum’ species from ash tree infesting psyllids. Phytopathology 112(1),76-80.