Résumé
The increasing concern of authorities for the public living in residential areas close to crops fields has raised several issues related to plant protection applications. First, the limited capability of existing regulations (EFSA Guidance, 2013) does not help to consider, directly into the registration dossier, drift reducing techniques (DRT) providing a drift reducing ratio (DRR) higher than 50%. Second, bystander exposure would benefit from the use of existing DRTs, in a post-registration management scheme, but the current knowledge is rather limited for a wide range of crop contexts (Mercier, 2020, Buttler et al., 2010). Third, there is a need to better characterize the benefit of the combination of existing DRTs with physical barriers like natural or artificial hedgerows or nets. The CAPRIV Project aimed at studying some solutions to conciliate PPP applications with the preservation of residential areas. This two-year project (2020-2021) was funded by the French Ministry of Agriculture and was led by a consortium of researchers from INRAE and agronomists from Technical Institutes for Cereals (ARVALIS), Vines and Wine (IFV) and Fruits and Vegetables (CTIFL). The project was coordinated by the National association of technical Institutes (ACTA) and the French Agency for Food Safety and the Environment (ANSES) was associated to the work. Several work packages were implemented. WP1 aimed at defining consistent spraying references as well as comparable protocols and result format for the evaluation of sedimentation spray drift in Petri dishes, airborne spray drift (PTFE monofilaments) and bystander dermal exposure (cotton T shirts) through the collection of a fluodye (Grimbuhler and Viel, 2024). In particular, means to aggregate results like averages per distance or height, step by step comparison, or through the area under the drift curve (AUC) were defined. A selection of about four different DRTs were tested in each crop context with several DRR levels for nozzles (case of field crop sprayer), or spraying technologies (vineyard and orchard sprayers) in WP2. A different physical barrier was selected for each crop system based on existing facilities in WP3. And a final WP4 aimed at developing a platform for modelling based on these scenarios. In total more than 6000 individual samples were analysed and some raw data are already available for field crop sprayer (Perriot et al., 2023) and vineyard sprayers (Verges et al., 2024). Due the number of modalities tested; results were analysed considering graduated approaches. In a first approach, the comparison of the drift reducing performance of DRTs as measured through sedimentation (1 to 20m downwind) and airborne spray drift captured at 5m downwind was achieved. In most cases, the DRR based on airborne spray drift was lower than for sedimentation spray drift but the order of magnitude was similar. Since the airborne drift catchment was realized at a downwind distance of 5m from the last row, the sensitivity to finer droplets is higher compared to the sedimenting protocol. Under these conditions, low drift nozzles are the favored. In a second approach, the effect of the combination of physical barriers with DRT was evaluated. Physical barriers showed an intrinsic DRR of 25% to 33% depending on the type of barrier when tested with a reference spraying condition. In most cases, the combination of the DRT and physical barriers led to higher resulting DRR than the arithmetic combination of DRTs of both since the level of deposit became sometimes difficult to detect. In a third approach, the effect of DRT on residents dermal exposure was tested. For example, the effect of the sampling distance on mannequins was particularly visible. An example is given for the vineyard case. Many results are still under analysis but examples from different cropping contexts will be highlighted.