The WUR Drift Calculator for estimating downwind deposits of spray drift

Summary

In 2003 the IMAG Drift Calculator was developed to compute downwind spray deposits onto surface water. Recently, it was renewed, improved and expanded resulting in the WUR Drift Calculator (WDC). The calculator is a tool to quantify spray drift deposits onto non-target areas downwind from a treated field. The calculator uses statistically obtained regression curves to calculate downwind spray deposition next to the sprayed field. These spray drift curves are derived from experimental data on drift deposition for field crops, fruit orchards and avenue tree nurseries. The WDC has two major evaluation goals. The first goal is the computation of spray drift deposits onto an edge-of-field watercourse next to an arable crop, fruit orchard or avenue tree nursery. Secondly, spray drift deposits onto off-field terrestrial non-target zones can be computed to evaluate exposure of non-target terrestrial plants (NTP) and arthropods (NTA) to pesticides. Drift mitigation measures such as additional buffer zones and the use of drift reducing application techniques (DRTs), can be selected as well. For field crops, a distinction is made between applications on bare soil (including low-height emerging crops) and applications on higher or full-grown crops. For fruit orchards, dormant trees and trees in full leaf are distinguished. With avenue tree nurseries, a distinction between spindle trees, transplanted trees and high avenue trees is made. The WDC follows the current regulations and measures described in the Environmental Activity Decree of the Dutch Ministry of Infrastructure and Water Management. For arable crops, the Dutch crop definition list (DTG list) is implemented to predefine the settings of the boom sprayer (including DRT class) and crop-free buffer zone. The WDC has been implemented by the Dutch Ctgb as a mandatory tool since January 2022. It can be downloaded free of charge.