Plant-inhabiting predatory mites possess several traits that make them ideal model species for exploring their species richness and diversity. First, these mites are important indicators in agroecosystems, as they serve as efficient natural enemies of pest species. Second, intensive research over the last seven decades has led to the discovery of new species, resulting in a twentyfold increase in recorded species richness. Third, these minute mites complete their entire life cycle primarily on the lower surface of plant leaves, making them ideal sampling units and, at the same time, relevant bioindicators for management intensity. We sampled these mites in apple orchards differing in management regime (extensive, organic and integrated). The objectives were to assess the sampling effort; identify appropriate diversity indexes; and compare the effects of management practices on mite diversity. Extensive (no use of chemicals; meadow orchards), organic (use of limited certified pesticides) and integrated (additional use of synthetic pesticides) apple orchards were located in south-eastern Austria. Eight leaves per tree were sampled once per month from August to October 2023. Mites were then identified at species level. We used rarefaction and extrapolation curves to estimate the sampling effort. The following diversity metrics were estimated: richness S, Menhinick’s index, Shannon diversity, Simpson diversity, and Simpson evenness. The rarefaction and extrapolation curves verified that the number of samples was sufficient to detect nearly all predatory mite species, regardless of the management system. However, only samples with S (number of species) > 1 can be used for calculating the Simpson evenness, which would result in a high loss of samples (57%). Thus, this index was not applied for the estimation of evenness. Twelve Phytoseiidae species were identified in the extensive meadow orchards: three species at high densities (Kampimodromus aberrans, Phytoseius horridus, Typhlodromus (Anthoseius) georgicus), five species at low densities, and four rare species. In contrast, predatory mite richness and diversity were low in organic and integrated orchards, where a single highly dominant species (Typhlodromus pyri) prevailed, accompanied by three to four species in low densities. This pattern might be related to the high pesticide input in organic and integrated systems. These strong management effects on species richness and diversity were supported by the metrics richness S, Shannon- and Simpson diversity, but not by the Menhinick’s index. This research was funded by the Austrian Climate and Energy Fund (48407317).