Tracking vectors of bacteria and phytoplasma threatening our carrot production

Several harmful phytoplasmas and bacteria such as Aster Yellows phytoplasmas (AY phytoplasma) or ‘Candidatus Liberibacter solanacearum’ have an important impact on our carrot production. These ob-ligate phloem pathogens are also threatening other Apiaceae, such as celery, and even our potato in-dustry. These pathogens are mainly transmitted by phloem and xylem feeding insects belonging to the Auchenorryncha or Sternorrhyncha, commonly referred to as leaf-, plant- and treehoppers, as well as psyllids. However, for many of them, transmission of the diseases has not yet been investigated. Knowledge on vectors involved, their phytosanitary status in specific areas, their host range, alternative hosts, and influence of abiotic factors on the vector occurrence and disease transmission capacity is fragmented or lacking. A comprehensive scientific insight is indispensable in order to improve risk eval-uation and define effective regulation and phytosanitary management strategies adapted to local con-ditions for this type of vectored plant diseases. One of the selected crops for which a 2-year intensive vector survey was organised, was carrot. Two of these fields appeared to be infected with both AY phytoplasma and ‘Ca. L. solanacearum’. A number of widely used trapping methods were compared, proving sticky traps to be the most effective. The known vector Macrosteles sexnotatus, as well as the experimental phytoplasma vector Empoasca decipiens (most abundant in summer), Zyginidia scutel-laris (most abundant in autumn) and other species such as Javesella pellucida and E. atropuncata were found and population dynamics were assessed. The number of psyllids that were collected from the carrot fields was rather limited. The (potential) vectors were tested for the presence of the phytoplas-mas and ‘Ca. L. solanacearum’ and an overview of positive testing insects will be presented and further investigated through transmission trials.

Publication year:2018