Interspecific interactions within a vector-borne complex are influenced by a co-occurring pathosystem.

Potato virus Y (PVY) and zebra chip (ZC) disease are major threats to solanaceous crop production in North America. PVY can be spread by aphid vectors and through vegetative propagation in potatoes. ZC is associated with "Candidatus Liberibacter solanacearum" (Lso), which is transmitted by the tomato/potato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae). As these two pathosystems may co-occur, we studied whether the presence of one virus strain, PVY°, affected the host preference, oviposition, and egg hatch rate of Lso-free or Lso-carrying psyllids in tomato plants. We also examined whether PVY infection influenced Lso transmission success by psyllids, Lso titer and plant chemistry (amino acids, sugars, and phytohormones). Lso-carrying psyllids showed a preference toward healthy hosts, whereas the Lso-free psyllids preferentially settled on the PVY-infected tomatoes. Oviposition of the Lso-carrying psyllids was lower on PVY-infected than healthy tomatoes, but Lso transmission, titer, and psyllid egg hatch were not significantly affected by PVY. The induction of salicylic acid and its related responses, and not nutritional losses, may explain the reduced attractiveness of the PVY-infected host to the Lso-carrying psyllids. Although our study demonstrated that pre-existing PVY infection can reduce oviposition by the Lso-carrying vector, the preference of the Lso-carrying psyllids to settle on healthy hosts could contribute to Lso spread to healthy plants in the presence of PVY infection in a field.