Abstract
Simple SummarySustainable agriculture becomes more important for biodiversity conservation and environmental protection. Viticulture is characterized by relatively high pesticide inputs, which could decrease arthropod populations and biological pest control in vineyards. This problem could be counteracted with management practices such as the implementation of diverse vegetation cover in the vineyard inter-rows, reduced pesticide input in integrated or organic vineyards, and a diverse landscape with trees and hedges. We examined the influence of these factors on predatory mites, which play a crucial role as natural enemies for pest mites on vines, and pollen as important alternative food source for predatory mites in 32 organic and integrated Austrian vineyards. Predatory mites benefited from integrated pesticide management and spontaneous vegetation cover in vineyard inter-rows. Pest mite populations were very low and sometimes completely absent on vines. This showed that agri-environmental schemes should consider less intensive pesticide use and spontaneous vegetation cover in the vineyard inter-row due to the beneficial effect on predatory mite populations and their related biological control potential in vineyards.Viticultural practices and landscape composition are the main drivers influencing biological pest control in vineyards. Predatory mites, mainly phytoseiid (Phytoseiidae) and tydeoid mites (Tydeidae), are important to control phytophagous mites (Tetranychidae and Eriophyidae) on vines. In the absence of arthropod prey, pollen is an important food source for predatory mites. In 32 paired vineyards located in Burgenland/Austria, we examined the effect of landscape composition, management type (organic/integrated), pesticide use, and cover crop diversity of the inter-row on the densities of phytoseiid, tydeoid, and phytophagous mites. In addition, we sampled pollen on vine leaves. Typhlodromus pyri Scheuten was the main phytoseiid mite species and Tydeus goetzi Schruft the main tydeoid species. Interestingly, the area-related acute pesticide toxicity loading was higher in organic than in integrated vineyards. The densities of phytoseiid and tydeoid mites was higher in integrated vineyards and in vineyards with spontaneous vegetation. Their population also profited from an increased viticultural area at the landscape scale. Eriophyoid mite densities were extremely low across all vineyards and spider mites were absent. Biological pest control of phytophagous mites benefits from less intensive pesticide use and spontaneous vegetation cover in vineyard inter-rows, which should be considered in agri-environmental schemes.
Highlights
Plant diversity at the local and landscape scale plays a crucial role for herbivorous pest species, natural enemies, and their interactions in agroecosystems [1,2,3]
Phytoseiid mite densities increased with higher proportion of vineyards at the landscape scale
The categorical toxicity rating for T. pyri showed no correlation with the predatory mite densities. We suggest that this could be related to the higher pesticide resistance of T. pyri field populations [127] compared to lab strains, which are usually used for ecotoxicological tests [128]
Summary
Plant diversity at the local and landscape scale plays a crucial role for herbivorous pest species, natural enemies, and their interactions in agroecosystems [1,2,3]. Large crop monocultures in simple landscapes could promote pest outbreaks because of two main reasons: (1) food is not a limiting resource for herbivores, specialized to feed on the crop species in monocultures (i.e., resource concentration hypothesis), and (2) the lack of alternative food resources, oviposition sites, overwintering locations, and shelter for natural enemies hinder their permanent establishment in monocultures (i.e., natural enemy hypothesis) [2,4,5,6]. The nearly unlimited food resources and the lack of natural enemies constitute ideal conditions for specialized herbivores in such agroecosystems. Pest abundance might be dependent on non-crop habitats as alternative food resources or for overwintering [7], which could limit the positive feedback of simple landscapes for pest outbreaks. Studies evaluating the natural enemy hypothesis [4,5] have provided divergent results—high plant diversity increased the abundance of natural enemies, resulting in lower pest densities in peach orchards and cacao agroforestry systems [8,9], whereas such positive plant diversity effects were not observed in annual crops such as squash and cabbage [10,11].
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