First Insights into Drift Capture Efficiency of Non-Target Terrestrial Plants

In this upload, three different publications (one presentation deck and two conference papers) are combined that all deal with the topic of plant protection product spray drift exposure of Non-Target Terrestrial Plants. To determine pesticide spray drift exposure of non-target organisms for the risk assessment, drift deposition to horizontal collectors like petri dishes is currently used. There is little information about the volume of airborne drift captured by vertical, 3-D off-crop structures, such as plants. Preliminary wind tunnel investigations indicated that rows of plants capture similar volumes as single plants but that blocks of plants differ in the quantity captured. The front row of plants in a block, unsurprisingly, captures the most spray drift while a few rows back, the amount captured falls off considerably. There are also differences in spray drift capture depending on plant species. The results support the assumption that the standard regulatory spray drift exposure estimations based on horizontal collection do not reflect the reality of spray drift capture by off-crop canopies. Development of new testing and modelling based approaches would allow for a more realistic risk assessment. There is interest in developing approaches to higher tier testing, for non-target terrestrial plants, as an alternative to field trials which are expensive and not standardized. Developing modelling or novel experimental methods requires the main factors that determine exposure and biological effect to be taken account of appropriately. Droplet size is likely to be one of the most important parameters to be considered, and so in this study, both modelling and wind tunnel experiments were used to explore some of the factors that influence the size distribution of droplets that reach downwind non-target plants. These factors include wind speed, distance downwind and nozzle design.