County-level patterns in contact (a,b) and oral (c,d) bee toxic load of agricultural insecticides in 2012 (a,c) and fold change from 1997–2012). Toxic load is normalized by the total area (ha) of each county, to account for variable county size. Note that California data excludes seed-applied insecticides. Color scales are based on Jenks natural breaks, which maximize similarity within classes and minimize similarity between classes, adjusted for (b,d) to center on zero. Black outlines show USDA Farm Resource Regions. Maps were created using the R statistical language version 3.6.1 (https://www.R-project.org) using the data generated in this study.