Gone with the wind: Aerial dispersal of Parthenolecanium corni crawlers in a newly planted grapevine plot

Soft scales nymphs are suspected to propagate grapevine leafroll viruses in the vineyard, while moving from vine to vine, but results of long distance dispersion, especially those due to wind, are poorly known. Thus, a net of sticky cylindrical traps was placed in a newly planted grapevine plot to evaluate aerial dispersal of Parthenolecanium corni (Hemiptera Coccidae) nymphs. The plot was surrounded by vine plots infested by this species. Number of crawlers collected on traps was generally higher on the trap side exposed downwind and depended on population density of neighbouring vines. Coloured glitters of size and weight similar to that of crawlers were used to simulate wind transport. The highest number of glitters was trapped at the prevailing wind sector. A majority of glitters was found on traps close to dispersion cups, and the most remote were collected up to 165m away from glitter source. Wind dispersal of crawlers was confirmed by colonisation of the new vine plot by P. corni, 2years after plantation. The settling of P. corni on the young plot displayed no significant structure, as expected from a wind dispersal. Although grapevine leafroll viruses and Grapevine virus A were detected by reverse transcription-polymerase chain reaction in several batches of trapped nymphs, these viruses were not found in vines colonised by P. corni in the new plot within the 4years following plantation.