Bactericera trigonica and B. nigricornis (Hemiptera: Psylloidea) in Tunisia as potential vectors of “Candidatus Liberibacter solanacearum” on Apiaceae

A new vegetative disorder was observed in Tunisian carrot (Daucus carota subsp. sativus) fields consisting of leaf curling, a yellowish purply-bronze discolouration of the leaves, as well as a stunted carrot shoots with an abundance of secondary roots. The causal agent was recently proven to be a bacterium ’Candidatus Liberibacter solanacearum’ (Lso) which infects plants and seeds. Subsequently, using multiple sampling techniques, a wide-scale survey was carried out in all the symptomatic areas in order to identify the insects potentially capable of vectoring the bacterium. This revealed in all the symptomatic carrot fields two psyllid species, Bactericera trigonica and B. nigricornis (Förster, 1848), never before reported in Tunisia and shown in the literature to be vectors of Lso. In addition to carrot, surveys across Tunisia found these psyllid species on other host plants belonging to the Apiaceae family, such as wild fennel, celery and parsley, and confirmed the diversity of their host range and their potential to develop on many wild and cultivated plants. The possible phytosanitary risks which derive from the presence of these two insects on carrot and associated crops are discussed as well as their potential role as vectors of Lso.