UC Davis

This thesis assesses the environmental impact of insecticides applied during a 10- year extension project conducted across Mexico by the International Maize and Wheat Improvement Center (CIMMYT). Utilizing the internationally recognized USEtox model, we calculated the freshwater ecotoxicity of over 46,000 applications of insecticides from a dataset collected by CIMMYT since 2012. The database not only includes informa- tion on active ingredients applied but also on management practices and two extension approaches: traditional extension services and so-called innovation modules, which involve side-by-side comparisons of conventional and recommended applications of in- secticides. This study provides a unique opportunity to apply USEtox to real-life data that has been collected over more than a decade, using it as a tool to evaluate an extension project. Results reveal substantial variability in terms of the ecotoxicity of active ingredi- ents applied, with some active ingredients being substantially toxic even in small doses applied compared to other active ingredients, highlighting the importance of includ- ing as much data in impact assessments as possible. Not only did we calculate the most and least toxic active ingredients, but we also plotted trends over time. These revealed partial success in reducing the environmental footprint of the extension effort. Additionally, we could show which management practices and extension modes were associated with lower freshwater ecotoxicity scores. This study not only contributes to advancing the application of USEtox in real-life scenarios but also highlights the importance of field-based data and standardized models to make recommendations for agricultural pest management practices to lower their impact on the environment.