Honeybee toxicity of pesticides used in United States maize and soybean production, 1998-2020.

Pesticides are widely used around the world and have demonstrated benefits to crop production. However, pesticides have also been associated with negative impacts to nontarget organisms, including pollinators. Here, we combined pesticide usage and toxicity data to create a toxicity index, which shows that pesticide hazard to honeybees (Apis mellifera) has changed substantially in U.S. maize (Zea mays) and soybean (Glycine max) production between 1998 and 2020. To reduce potential risks to honeybees and increase the eco-efficiency of crop production, efforts should be made to refine management strategies for pests that contribute most to the honeybee toxicity index. In maize, Coleoptera and Lepidoptera pests drive pesticide usage most responsible for hazard to honeybees, although the relative hazard from targeting those pests has decreased over time. In soybean, hemipteran pests were the largest relative contributor to insecticide honeybee hazard. Specific pests that contributed to honeybee toxicity hazard included corn rootworm species (Diabrotica spp.), silk-eating insects, and cutworms in maize, and stink bugs (family Pentatomidae) and aphid species (Family Aphididae) in soybean. We combined crop yield data with the toxicity index to quantify the eco-efficiency, a measure of crop yield per unit of toxicity hazard. While crop yield for both maize and soybean increased steadily throughout the study period, eco-efficiency decreased in both crops between 2012 and 2020, suggesting increases in crop yield have failed to keep pace with increases in insecticide hazard to honeybees.