Phytophagous mites and their predators during the establishment of apple orchards under biological and integrated fruit production in Central Otago, New Zealand

Abstract

Phytophagous mites and their predators were monitored from 1994 to 2000 on a range of cultivars of apple trees under biological fruit production (BFP) and integrated fruit production (IFP) methods, and compared with those on trees sprayed with an organophosphate insecticide programme (OPP). Two-spotted spider mite (TSM) was the dominant mite pest but it remained below economic thresholds under BFP and IFP, primarily through predation by Galendromus occidentalis, assisted by a range of other predatory mites and insects. The latter were largely absent under OPP, and OP-resistant G. occidentalis were unable alone to prevent TSM from causing unacceptable fruit infestation at harvest in some seasons. High populations of apple rust mite (ARM), Aculus schlechtendali, provided a valuable food source for G. occidentalis under BFP and IFP that was not available under OPP. Similarly, the use of acaricidal sulphur and lime sulphur as trial fungicides in the BFP orchard greatly reduced ARM density and disrupted phytoseiid control. European red mite (ERM), Panonychus ulmi, caused no economic damage in any production system, primarily because of predation by Typhlodromus pyri. The density of the anthocorid Orius vicinus, which feeds on ERM and TSM, was shown across all three production systems to be dependent on the density of ARM on the foliage, but no such relationship was found for the mirid Sejanus albisignata. This research has provided further evidence of the need to find alternative disease management strategies for organic production to substitute for the broad-spectrum fungicidal, acaricidal and insecticidal impacts of sulphur and lime sulphur.