Hedges as potential sources ofTyphlodromus pyri,the most important predatory mite in vineyards of Northern Switzerland

This paper presents the results of an acarological survey started in 1984 in hedges bordering vineyards in Northern Switzerland where natural populations of the economically important predatory miteTyphlodromus pyri occur. The objective of these investigations was to identify those plant species in the hedges and forest margins adjacent to vineyards that carry high populations of this important predator, and to evaluate the potential role of hedges as ecological refuges and sources ofT. pyri. We found high and consistent densities ofT. pyri onRubus fruticosus, and less regularly onCornus sanguinea, Corylus avellana andLonicara xylosteum. We conclude that hedges can provide ecological refuges and sources of this economically important predatory mite where earlier applications of inappropriate pesticides have eliminated these important antagonists. However, the inoculative release ofT. pyri along with the increase of the internal ecological diversity of the vineyard achieved by proper management of the green over plants (“weed”) will have a strong influence on predator densities within the vineyards.