In a study with the leafhopper Euscelidius variegatus (Kirschbaum) (Cicadellidae: Deltocephalinae), it was found that when a dual infection of the phytoplasma subgroup 16SrI-B or chrysanthemum yellows (CYP) and subgroup 16SrV or Flavescence dorée phytoplasma (FDP) occurred, CYP was not affected by FDP, while FDP was suppressed by CYP regardless of the order of infection. The gene discussed is PPIG; the disease is infection.