The last 10 years have seen a surge in the use of tiny substances called nanomaterials in agrochemicals like pesticides and fungicides. The idea is to provide more disease protection and better yields for crops, while decreasing the amount of toxins sprayed on agricultural fields. But when combined with nutrient runoff from fertilized cropland and manure-filled pastures, these ‘nanopesticides’ could also mean more toxic algae outbreaks for nearby streams, lakes and wetlands, researchers report.