Abstract‘Bois noir’ (BN) and flavescence dorèe (FD), the two main diseases of the grapevine yellows complex associated with genetically distinct phytoplasmas, have a complex epidemiology including multiple insect vectors and reservoir plants. This study investigated the presence of BN and FD phytoplasmas in nine groundcover plant species commonly utilized for inter-row vineyard green manure in Franciacorta (North Italy). The activities conducted in 2020 included monitoring and sampling groundcover plant species and symptomatic grapevines in September, and phytoplasma identification and typing by amplification and sequence analyses of stamp and map genes. Molecular analyses identified BN phytoplasma (strains carrying the stamp gene sequence variants St5, St19, St30) and FD phytoplasma (strains carrying the map gene sequence variant M54) in 72% and 28% of symptomatic grapevines, respectively. BN phytoplasma strains St5 and St30 were found also in Eruca sativa, Vicia sativa, and Polygonum fagopyrum. FD phytoplasma strain M54 was found also in Vicia faba, Trifolium incarnatum, and Polygonum fagopyrum. These results reinforced the evidence of the increasing range of BN and FD phytoplasma alternative plant hosts and suggested a criterium for the selection of the groundcover plant species utilized for green manure, excluding the ones putatively involved in BN and FD diffusion.

Scaphoideus titanus is the main vector of phytoplasmas associated with Flavescence dorée (FD), one of the most serious threats to viticulture in many European countries. To minimize the spread of this disease, mandatory control measures against S. titanus were decided in Europe. In the 1990s, the repeated application of insecticides (mainly organophosphates) proved to be an effective measure to control the vector and the related disease in north-eastern Italy. These insecticides and most of the neonicotinoids were recently banned from European viticulture. Serious FD issues detected in the recent years in northern Italy could be related to the use of less effective insecticides. Trials aimed at evaluating the efficacy of the most used conventional and organic insecticides in the control of S. titanus have been performed in semi-field and field conditions to test this hypothesis. In efficacy trials, carried out in four vineyards, etofenprox and deltamethrin proved to be the best conventional insecticides, while pyrethrins were the most impactful among organic insecticides. Insecticide residual activity was evaluated in semi-field and field conditions. Acrinathrin showed the most significant residual effects in both conditions. In semi-field trials, most of the pyrethroids were associated with good results in terms of residual activity. However, these effects declined in field conditions, probably due to high temperatures. Organic insecticides showed poor results in terms of residual efficacy. Implications of these results in the context of Integrated Pest Management in conventional and organic viticulture are discussed.