Efficacy of Conventional and Organic Insecticides against Scaphoideus titanus: Field and Semi-Field Trials

SIMPLE SUMMARY: The efficacy of conventional and organic insecticides on nymphs and adults of Scaphoideus titanus, the main vector of phytoplasmas associated with the grapevine yellow Flavescence dorée, was evaluated. In trials carried out in the open field, etofenprox and deltamethrin proved to be the best conventional insecticides, while pyrethrins were the most impactful among organic insecticides. Insecticide residual effects were evaluated in semi-field and field conditions. Acrinathrin showed the most significant residual effects, followed by other pyrethroids. Organic insecticides gave poor results in terms of residual efficacy. In field trials there was a loss of residual activity coinciding with higher temperatures. Implications for S. titanus control strategies are discussed. ABSTRACT: 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.