Does minimal pruning and reduced fungicide use impact spiders in the grapevine canopy?

Abstract

Agricultural management should aim at high densities of beneficial organisms such as spiders. Here, we asked whether spiders in vineyards can be promoted either by using novel disease resistant grape varieties that allow for a reduced number of fungicide applications, or by minimal pruning which enhances the structural complexity of the grapevine canopy. We compared spider communities in vineyards planted with fungus-resistant varieties (PIWIs) to vineyards with traditional grapevine varieties, and minimally pruned vineyards to vertical shoot positioned vineyards. Densities of Theridiidae were more than doubled in fungus-resistant grape varieties, but the remaining families were not significantly affected. Minimal pruning enhanced Philodromidae and Dictynidae but reduced Salticidae. However, neither pruning method, nor the reduced fungicide use in PIWI vineyards, had significant effects on overall spider abundance or species richness. Hence, effects of vineyard management were family-specific and possible consequences for pest regulation will thus depend on the pest control potential of the involved families.