Effect of Leaf Removal and Insecticide Applications on Population Densities of Leafhoppers and Mites Associated with Grapevines

SIMPLE SUMMARY: A study was conducted in two vineyards located in Northern Italy to investigate the effects of mechanical leaf removal, insecticide application, and their interaction on grapevine arthropods. The results showed that the use of insecticides reduced the population densities of leafhoppers and predatory mites. Mechanical leaf removal had a greater impact on the populations of predatory mites compared to leafhoppers. Interestingly, in one of the vineyards, phytophagous mite populations increased some weeks after both leaf removal and insecticide application. These effects are discussed within the IPM framework. ABSTRACT: In this study, we tested the effects of mechanical leaf removal, insecticide application, and their interaction on leafhoppers and phytophagous and predatory mites occurring in two vineyards over three growing seasons. Leaf removal was performed in the fruit zone using a two-head pulsed air leaf remover, while insecticides were applied with a tunnel air-assisted sprayer at the maximum dose/ha recommended on the product label. Results demonstrated the efficacy of insecticide application in reducing the population densities of leafhoppers but also their detrimental effects on predatory mites. In a number of case studies, leaf removal reduced leafhopper and predatory mite densities. In one vineyard, phytophagous mite populations increased some weeks after leaf removal and insecticide application, highlighting the need to carefully consider the potential impact of vineyard management practices on non-target arthropods in the IPM framework.