Regulated dose adjustment of commercial orchard spraying products

Abstract A generalised model of regulated dose adjustment is formulated to examine the potential for reducing the usage of commercial orchard spraying products. The model considers the harmonised regulations for pesticide registration and spray interception by different orchard structures with different distributions of target pest/disease across the tree-row. Different orchard structure standards (i.e. the values of orchard structure parameters that define the limits for safe and efficacious dose adjustment) are used to model the real-world operational constraint of different product types as they are established by the pesticide registration process (i.e. maximum Ground Area (GA) dose rate for safe product use and the manufacturer's Leaf-Wall-Area (LWA) dose rate for efficacious product use). To eliminate the need for a recommended LWA dose rate on the product label a standard ratio of tree height to row spacing is used to express the intersection between the limits for safe and efficacious product use. Light Detection and Range (LiDAR) recordings of commercial pome-fruit orchards are used to determine model inputs. The LiDAR recordings, selected for use in this study, represent a typical sample distribution of commercial orchards of different: tree size, density, cultivation-method, growth-stage, age and variety. The model outputs obtained from LiDAR recordings are grouped to represent the typical uses of different product types, defined by orchard growth-stage and target pest/disease distribution across the tree-row-width. The generalised model of regulated dose adjustment predicts pesticide usage levels in the range 43%–60% of maximum GA dose rate, depending on product type, with very low liability risk to pesticide manufacturers for reduced product efficacy ( c . 1 in 200). This compares with predicted usage levels of (72%–88% of maximum GA dose rate) for the equivalent LWA model. The generalised model of regulated dose adjustment will therefore be needed to provide support for new spraying technologies and regulations in order to achieve the full potential for reducing the use of orchard spraying products as pressure for more sustainable fruit production increase in the future.