Environmental Project No. 1178 2007 – Evaluation of Pesticide Scenarios for the Registration Procedure

Evaluation of Pesticide Scenarios for the Registration Procedure

6. Conclusions

This study evaluates the reliability and representativeness of both the existing model scenarios (Langvad, Karup, and Hamburg) and the recent PLAP scenarios (Jyndevad, Tylstrup, Silstrup, Estrup, and Faardrup) with the purpose of recommending the two scenarios to be used in the coming registration procedure.

The PLAP scenarios Jyndevad (sand) and Silstrup (clay) are proposed for future use in the Danish pesticide approval procedure. Given the lack of criteria defined by the Danish EPA, this recommendation is based on characterization with respect to precipitation, geology, reliability of field data and conceptual model. Additionally it is based on the authors´ assumption that choosing the worst case scenarios with respect to leaching will best protect the Danish groundwater against pesticides.

The existing scenarios (Karup, Langvad, and Hamburg) were found to be less restrictive than some of the PLAP scenarios. For the sandy scenarios, the highest leaching was found at Jyndevad. The somewhat lower leaching at Karup resembles that of Tylstrup, while that of Hamburg is generally lower. For clay scenarios the leaching at Langvad is higher than that at Faardrup but considerably lower than that of Silstrup and Estrup. These conclusion were based upon modelling results covering a 20 years period where 1 kg/ha of pesticides was applied every year to either spring cereals or winter cereals. Crop parameters, dose and application time of pesticides and pesticide properties were kept the same in all scenarios. The numerical model used for setting up the scenarios comprised PELMO 3.2 (Hamburg), MACRO 4.4.2 (Langvad and Karup) and the recent MACRO 5.1 (the PLAP-scenarios: Tylstrup, Jyndevad, Silstrup, Estrup, and Faardrup).

Often, when comparing pesticide leaching for different scenarios, the question arises, if the ranking of scenarios with respect to leaching is dependant on e.g. choice of pesticide and application date linked with plant evolution. The latter is studied in a sensitivity analysis for the five PLAP scenarios, where the application dates are changed approximately three weeks. Changing the application date and related plant evolution may influence pesticide leaching and subsequent the approval of pesticides.