XVII Pesticide Symposium Piacenza – Workshop

XVII Pesticide Symposium Piacenza – Workshop Proposal (1/2 Day)

September 3, 2024 (afternoon)


Quantitative mitigation of runoff of pesticides in regulatory assessments with VFSMOD

This workshop aims at introducing the most recent version of VFSMOD with several mechanistic upgrades, new VFS filter strip scenarios, and the new SWAN user shell. VFSMOD is a mechanistic model that predicts the reduction of run-off, erosion, and pesticide transport by vegetated filter strips. Unlike the current FOCUS (2007) approach with its fixed reduction factors that are not dependent on event magnitude or other environmental conditions, VFSMOD calculates the reduction based on environmental conditions and hydraulic load (volume of water inflow per VFS area), i.e., the most critical factors for VFS efficiency. Sound exposure assessments require a dynamic, event-based, and widely tested model such as VFSMOD. It is also the modelling tool recommended by the MAgPIE (2017) working group to assess VFS performance and has recently been endorsed in the CERSA workshop by North American regulators from USEPA, Canadian PMRA and Californian CDPR (Chen et. al, 2023), with an EPA PWC scenario parametrization report developed recently (Ritter et al., 2023).

Remaining issues in VFSMOD flagged by MAgPIE related to the empirical pesticide trapping equation by Sabbagh et al. (2009) have meanwhile been resolved with the introduction of the mechanistic pesticide equation by Reichenberger et al. (2019). Recently, a multiple-regression equation derived from a powerful machine-learning-based approach has been developed, tested, and implemented in VFSMOD to dynamically estimate the incoming sediment characteristics, which is the most critical parameter that determines the reduction of eroded sediment load by the VFS (Reichenberger et al., 2023). In addition, a new pesticide leaching and remobilization algorithm has been implemented, which allows for a more realistic prediction of residues that are trapped in the VFS and may be remobilized during a following run-off event (Muñoz-Carpena et al., 2022).

VFSMOD has been extensively tested against field studies. Hydrology and sediment trapping have been successfully validated in numerous studies (Muñoz-Carpena et al., 1999; Poletika et al., 2009; Muñoz-Carpena et al., 2010). The empirical pesticide reduction part has been assessed and validated with extensive experimental data (Sabbagh et al., 2009; Poletika et al., 2009; Winchell et al., 2011; Phillips et al., 2016; Reichenberger et al., 2019; Luo, 2019; Zhang et al., 2019). The mechanistic mass-balance equation for pesticide trapping has been validated in Reichenberger et al. (2019) along with the development of a large validation dataset to complete the full mechanistic set-up of the model.

For regulatory quantitative pesticide mitigation, new VFS scenarios have been developed for all four FOCUS run-off scenarios (R1 – R4) to ensure that a realistic worst-case pesticide trapping efficiency (10th percentile) is calculated for each of the scenario zones (Reichenberger et al., in prep.). For regulatory predictions the SWAN tool integrates PRZM, VFSMOD, the VFS scenarios, and TOXSWA in a user-friendly manner to calculate a FOCUS-compliant Step 4 surface water concentration (PECsw). VFSMOD integration in the FOCUS framework provides more realistic, although still protective, quantitative estimates of the pesticide reduction potential of vegetated filter strips compared to current simplistic fixed coefficients. Importantly, in accordance with the best scientific knowledge, these reductions can either be greater or smaller compared to the fixed reduction fractions from FOCUS (2007) based on the selected scenario / field conditions and event characteristics (Sur et al., 2019).VFSMOD is accepted in some EU member states for regulatory use and just recently its use on EU level has been approved by the endorsement of the Compendium of Risk Mitigation Measures by SCoPAFF, which can improve further regulatory uptake as it alleviates concerns about lacking harmonization (Read more in PDF).

Objective of the Workshop

We are aiming at a tripartite workshop with representation from academia, regulators, and industry to present, discuss, and assess the upgrades that have been added to VFSMOD including new VFS scenarios and the new SWAN user shell. It is proposed that the group kicks off an initiative to create a user manual or framework for the application of VFSMOD in regulatory simulations and dossiers (e.g., as a scientific paper in a SETAC journal).

Organizing and Scientific Committee

[NOTE: We are still looking for interested regulators and scholars to serve on the Scientific Committee. The tasks will be to set up the final agenda and to take part in the discussions.]



  • Rafael Muñoz-Carpena (U. of Florida, USA)
  • Roger Holten (NIBIO, Norway)
  • Others tbc



  • Robin Sur (Bayer)
  • Stefan Reichenberger (knoell)
  • Horatio Meyer (Bayer)
  • Peter Rainbird (Syngenta)
  • Bernhard Jene (BASF)
  • Amy Ritter (Waterborne)



  • José Luis and/or Elena Alonso Prados (Spanish Regulatory Agency)
  • Igor Kondzielski (IOŚ-PIB, Poland)
  • Others tbc