Invertebrate biodiversity in apple orchards: agrichemical sprays as explanatory variables for inter‐orchard community differences

Abstract

1 Invertebrates are important providers of ecosystem services to orchards and the orchards may benefit where there is greater biodiversity. Previous research has shown that apple orchards using organic or integrated pest management support different invertebrate communities, as can different orchards within the same management system. 2 In the present study, we examined the potential for agrichemical usage to explain inter-orchard invertebrate community differences in 10 New Zealand apple orchards under integrated pest management. 3 Multiple regression models were used to examine relationships between spray diary data and invertebrates collected by branch tapping, pitfall and sticky traps in 2011/2012. Insecticides, fungicides, plant growth regulators and fertilizers were used as explanatory variables in these models and the most parsimonious models were identified. 4 Plant growth regulators were significant in most of the models for inter-orchard variability in total invertebrate diversity. Insecticides featured strongly in models explaining pest assemblages, although not so strongly for models for their natural enemies. Fungicide and fertilizer use featured in models explaining communities of decomposers and fungivores. 5 The results generated several hypotheses about the impacts of specific agrichemicals on invertebrate biodiversity, which, if tested, could establish the feasibility of customizing spray schedules to meet both biodiversity and production goals. orchard to orchard depending on the demands of the site and the preferences of the manager. Similarly, those producing apples using the IFP system may employ a range of different practices to optimize the outputs from each orchard block and to meet specific production goals for access to particular markets. It appears likely that these differences in the suites of practices used in each orchard could at least partially explain inter-orchard variation in invertebrate diversity within a set of orchards using the same production system. If this is the case, then it raises the possibility of customizing management practices to support invertebrate communities that will fulfil particular biodiversity goals. Many factors can influence invertebrate populations in orchards, including agrichemical use, crop species, soil type, altitude, aspect, climate, seasons and weather. Neighbouring land uses, proximity of alternative resources for invertebrates, the composition of plant communities in the understorey and