Influence of nettle control along a ditch on spatial distributionof Hyalesthes obsoletus Signoret in a neighbouring vineyard

Abstract: The nettle (Urtica dioica L.) is the most important host plant for the phytoplasmaassociated with the Bois noir (BN) disease of the grapevine and for its vector, Hyalesthesobsoletus Signoret. A higher abundance of the vector inside the vineyards is favoured by thenettle growing in edge rows and surrounding ditches. Foliar applications of insecticides appearednot an effective measure for vector and disease control, whereas nettle control could be useful toreduce BN incidence in vineyards. In particular the efficacy of nettle control by selectiveherbicide applications in early autumn and early spring was demonstrated. Many authors havesuggested 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 researchwas to evaluate if nettle cutting during the adult flight favours the colonisation of the vineyardsby the vector. For this purpose, three different weed managements (no cut, one cut during adultflight, 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 wasrecorded by yellow sticky traps placed on herbaceous vegetation along the ditch and at differentpositions inside the vineyard. Results showed that nettle cutting induced a reduction in vectorpresence in the ditch, but favoured its dispersion inside the vineyard. The implications of theseobservations on disease control are discussed.