New mealybug species vectoring Grapevine leafroll-associated viruses-1 and-3 (GLRaV-1 and-3)

Many grape viruses, such as filamentous Grapevine leafroll-associated viruses in the Closteroviridae family, are spread primarily through infected propagating material. However, there is increasing evidence that leafroll disease are spread in the field by insect vectors, namely mealybugs and other scale insects. This study was carried out in the northern wine-growing regions of France where Grapevine leafroll-associated virus-1 and -3 (GLRaV-1 and -3) are the most widespread grape Ampelovirus species. The vineyards were inspected for presence of mealybug and scale insects and grapes infected by GLRaV-1 and -3. Mealybugs, Heliococcus bohemicus, Phenacoccus aceris (Pseudococcidae) and the soft scale insect Parthenolecanium corni (Coccidae), were capable of a transmission efficiency of 14%, 23% and 29% respectively. GLRaV-1 and -3 infections that resulted from virus transmission were confirmed with DAS-ELISA using polyclonal antibodies. This is the first report of GLRaV-1 and -3 transmission by mealybug and coccid species in France, and the first report of the ability of H. bohemicus and Phenacoccus aceris to transmit these viruses to grapevines. The relevance of these findings with regards to maintenance of virus-free grapevine stocks and to control leafroll spread in commercial vineyards is discussed.