Transmission of Grapevine virus A and Grapevine leafroll-associated virus 3 by Heliococcus bohemicus

Heliococcus bohemicus Sulc is very frequently found in vineyards in Northern Italy, where grapevine leafroll is widespread. Grapevine leafroll-associated virus 1 (GLRaV-1) and Grapevine leafroll-associated virus 3 (GLRaV-3) are also quite frequently observed, often in association with Grapevine virus A (GVA). The capacity of the mealybug to transmit these viruses to vine was therefore evaluated. Virus-free insects were fed on infected vines and then transferred to healthy test-plants. GLRaV-3 was transmitted to two out of 77 inoculated test-plants and GVA to one out of 38; GLRaV-1 was not transmitted. This is the first report of GVA transmission by H. bohemicus and the first report of the capacity of this mealybug to transmit GLRaV-3 to grapevine in Italy.