Pesticides can harm aquatic ecosystems and human health, so scientists need to understand how they move from farm fields into streams. A management tool commonly implemented is riparian buffers—strips of vegetation, like shrubs or grasses, bordering streams—that the U.S. Department of Agriculture (USDA) advises can reduce the amount of nutrients, sediment and pesticides getting into waterways. But it's unclear how effective buffers actually are at stopping pesticides from entering streams, accor...