Risk mitigation measures for diffuse pesticide entry into aquatic ecosystems: proposal of a guide to identify appropriate measures on a catchment scale.

Measures to mitigate the risk of pesticide entry into aquatic ecosystems are becoming increasingly more important in the management of hot spots of pesticide transfer; such management, for example, is required by the European Union's directive for the sustainable use of pesticides (2009/128/EC). Measures beyond those currently stipulated for pesticide product authorization may be needed. A concise compilation of the appropriate measures for users (that are primarily farmers but also, e.g., regulators and farm extension services) and a guide for practically identifying these measures at the catchment scale is currently not available. Therefore, a proposal was developed for a guide focusing on the most important diffuse entry pathways (spray drift and runoff). Based on a survey of exposure-relevant landscape parameters (i.e., the riparian buffer strip width, riparian vegetation type, density of ground vegetation cover, coverage of the water body with aquatic macrophytes, field slope, and existence of concentrated flow paths), a set of risk mitigation measures focusing on the specific situation of pollution of a water body catchment can be identified. The user can then choose risk mitigation measures to implement, assisted by evaluations of their efficiency in reducing pesticide entry, feasibility, and expected acceptability to farmers. Currently, 12 landscape-related measures and 6 application-related measures are included. The present guide presents a step toward the practical implementation of risk mitigation measures for reducing pesticide entry in aquatic ecosystems.