Species diversity, population dynamics and spatial distribution of mites on blackberry (Rubus ulmifolius Schott): A comparison between organic and conventionally-managed orchards.

We studied the species diversity of mites in five blackberry orchards [Rubus ulmifolius Schott (Rosales:Rosaceae)], three using organic production techniques and two conventional. Samples (n = 40 per orchard) were taken monthly over a period of eight months and each sample was comprised of leaves, flowers and fruits. We collected 16,667 mites in total; 1,391 specimens were mounted for identification. We analysed the population dynamics of the most abundant species and determined their spatial distribution using Spatial Analysis by Distance Indices (SADIE). We recorded 11 species from seven taxonomic families. The most abundant species throughout the study were Tetranychus urticae Koch (Acari: Tetranychidae) and Diptacus rubuscolum Trinidad, Duarte & Navia (Acari: Diptilomiopidae). Two predatory mite species were present in both production systems: Typhlodromalus peregrinus Muma and Neoseiulus californicus McGregor (Acari: Phytoseiidae). There was no significant relationship between the population dynamics of D. rubuscolum or T. urticae and either precipitation or temperature. The distribution of both these phytophagous species was generally aggregated and uniform. Overall, species diversity was significantly greater in conventional compared with organic production orchards, whereas mite abundance was greater in organic orchards compared with conventional orchards. [ABSTRACT FROM AUTHOR]