Neonicotinoids in U.S. Maize: Insecticide Substitution Effects and Environmental Risk

This study exploits a novel dataset containing more than 89,000 farm-level surveys over a 17-year period to investigate how neonicotinoid seed treatments in maize, now ubiquitous, have affected the use of other insecticides. Neonicotinoid insecticides are the most used class of insecticides in the world, but they are controversial because of their high toxicity to honeybees. In the United States, maize production accounts for the majority of neonicotinoid use, mostly as seed treatments. We find that neonicotinoids substituted for other major insecticides: plots planted with neonicotinoid-treated seeds were 52% and 47% less likely to be treated with a pyrethroid and organophosphate insecticide, respectively. Although honeybees have been put at greater risk by neonicotinoids, the changed pattern of pest control instruments has reduced toxicity risk for mammals, birds, and fish. We also find that adoption of genetically engineered insect-resistant maize varieties significantly reduced the use of organophosphate and pyrethroid insecticides, thereby reducing toxicity exposure to all examined taxa. Policies aimed at restricting neonicotinoid use may need to account for undesirable unintended consequences.