Neonicotinoids (NNIs) are the most widely used insecticides in the world. In theory, they are the perfect pesticide, coating the seeds of a crop so the growing plant is seeped in their poison, killing any munching marauder. No sloppy spraying, no residue, no toxic runoff into nearby streams - according to the marketing speak. In truth, however, NNIs are much less precise than advertised. They are persistent and water-soluble, so they do wash into streams and they target more than nibbling pests.