The nettle (Urtica dioica L.) is the most important host plant for the phytoplasma associated with the Bois noir (BN) disease of the grapevine and for its vector, Hyalesthes obsoletus Signoret. A higher abundance of the vector inside the vineyards is favoured by the nettle growing in edge rows and surrounding ditches. Foliar applications of insecticides appeared not an effective measure for vector and disease control, whereas nettle control could be useful to reduce BN incidence in vineyards. In particular the efficacy of nettle control by selective herbicide applications in early autumn and early
spring was demonstrated. Many authors have suggested that the nettle control applied during H. obsoletus flight could have negative effects, because the vector adults could be forced to migrate onto grapevines. The aim of this research was to evaluate if nettle cutting during the adult flight favours the colonisation of the vineyards by the vector. For this purpose, three different weed managements (no cut, one cut during adult flight, frequent cuts) were applied on the herbaceous
vegetation of a ditch bordering a vineyard. In this ditch, nettle was one of the principal components.
The flight dynamic of H. obsoletus was recorded by yellow sticky traps placed on herbaceous vegetation along the ditch and at different positions inside the vineyard. Results showed that nettle cutting induced a reduction in vector presence in the ditch, but favoured its dispersion inside the vineyard. The implications of these observations on disease control are discussed.