Vector Biology of the Soft Scales <i>Parthenolecanium corni</i> (Bouché) and <i>Parthenolecanium persicae</i> (Fabricius) (<i>Hemiptera: Coccidae</i>) With Grapevine Leafroll‐Associated Viruses and Grapevine Virus A

ABSTRACT Controlled experiments were conducted to enrich our knowledge on the transmission of different grapevine leafroll‐associated ampeloviruses (GLRaV‐1, ‐2, ‐3 and ‐4) by Parthenolecanium corni scale insect and to look for vector ability of Parthenolecanium persicae. GLRaV‐1 and the vitivirus GVA were transmitted by P. corni to healthy plants after acquisition on GLRaV‐1 and GVA‐infected grapevines ( Vitis vinifera ); however, GVA was not transmitted after acquisition either on GVA singly infected vines or Nicotiana benthamiana, or on purified GVA virions. These results support the hypothesis of ampelovirus assistance towards vitivirus during transmission. Transmission experiments with P. corni and different GLRaV‐4 strains showed a single transmission of strain 5. No transmission was observed with P. persicae after acquisition on GLRaV‐1, ‐3 and GVA coinfected source vines. P. corni L2 collected from an infected vine and placed on a nonhost plant tested positive for GLRaV‐1 and ‐3 until at least 30 and 50 days, respectively. These results contrast with the few days retention times generally reported in mealybugs. More work is needed to determine whether virions are conserved and, if so, their location inside the insects.