Spatially variable pesticide application in vineyards: Part II, field comparison of uniform and map-based variable dose treatments

Abstract

Reducing pesticide use is an important concern for many including the European Commission. One way to achieve this goal is to adjust the amount of pesticides in relation to canopy geometry and foliage. This objective currently poses an important challenge in vineyards with uniform vegetation but it is an added difficulty when the canopy shows spatial variability within the field. Is it possible to set a constant volume rate adjusted to this variability? Or is it more convenient to adjusting different volume rates based on a prescription map? Assuming a plant cell density (PCD) vegetation index from multispectral images to be optimal for detecting variations in vigour, two methods to adjust volume rates in spatially variable vineyards were proposed and tested: i) adjustment of a constant volume rate uniformly applied using a conventional sprayer, and ii) adjustment of two volume rates adapted to two vigour classes according to a prescription map. In both methods, PCD was previously correlated to the leaf area index (LAI), then taking the 70th percentile of LAI to determine adjusted volume rates through DOSA3D decision support system (www.dosa3d.cat/en). Leaf deposition with tracer was analysed to compare the proposed methods with the standard volume rate commonly used in the area. Statistical analysis showed no significant differences between treatments. Since pesticide savings can be achieved using the two methods, specifically 25.6% in adjusted uniform and 25.3% in adjusted map-based treatments, adjusted volume rate strategies can be recommended in vineyards with spatial variability.