County-level analysis reveals a rapidly shifting landscape of insecticide hazard to honey bees (Apis mellifera) on US farmland

Abstract

Each year, millions of kilograms of insecticides are applied to crops in the US. While insecticide use supports food, fuel, and fiber production, it can also threaten non-target organisms, a concern underscored by mounting evidence of widespread decline of pollinator populations. Here, we integrate several public datasets to generate county-level annual estimates of total ‘bee toxic load’ (honey bee lethal doses) for insecticides applied in the US between 1997–2012, calculated separately for oral and contact toxicity. To explore the underlying components of the observed changes, we divide bee toxic load into extent (area treated) and intensity (application rate x potency). We show that while contact-based bee toxic load remained relatively steady, oral-based bee toxic load increased roughly 9-fold, with reductions in application rate outweighed by disproportionate increases in potency (toxicity/kg) and extent. This pattern varied markedly by region, with the greatest increase seen in Heartland (121-fold increase), likely driven by use of neonicotinoid seed treatments in corn and soybean. In this “potency paradox”, farmland in the central US has become more hazardous to bees despite lower volumes of insecticides applied, raising concerns about insect conservation and highlighting the importance of integrative approaches to pesticide use monitoring.

Larval pesticide exposure impacts monarch butterfly performance

“…Several studies now confirm the presence of non-target pesticides in diets of pollinators foraging on non-crop, wild plants [4][5][6][7][8][9] . Much of these efforts focus on neonicotinoid insecticides due to their rapid adoption by farmers since the 1990s 10 , resulting in a dramatically higher toxic load for pollinators in agricultural landscapes 11,12 .…”

Beyond the Headlines: The Influence of Insurance Pest Management on an Unseen, Silent Entomological Majority

“…Contrary to popular belief, insecticide use in the U.S. continued to increase after Silent Spring, and those increases continue today (Mart, 2015). In the U.S., where Bt corn is rightly hailed as a target-specific and largely environmentally benign breakthrough in terms of reducing pesticide use (Dively et al, 2018), it is not common knowledge that virtually every kernel of Bt corn is treated with at least one neonicotinoid insecticide, and at steadily increasing levels (Douglas et al, 2020;Hitaj et al, 2020). It is also not widely reported that: (1) these insecticides target a suite of secondary pests that have historically been of only minor and sporadic economic importance, (2) are effective in a relatively short window of a maximum of 14-21 days following planting (Alford and Krupke, 2019), and that (3) most of the acres planted with Bt hybrids that include a neonicotinoid seed treatment are also likely to receive one or more applications of pyrethroid insecticides (United State Geological Survey National Water-Quality Assessment Project, 2020).…”

“…Surveying the current insecticide landscape in the United States reveals that a single class of compounds, the neonicotinoids, clearly stands above the others in terms of both the prevalence of use on the landscape and in terms of their potential toxicity to insects (DiBartolomeis et al, 2019;Douglas et al, 2020). Compared to older classes of insecticides, neonicotinoids were originally touted as being more selective because of their systemic nature (i.e., it was thought that only insects feeding on the crop would be exposed) and their apparently lower toxicity to mammals and other vertebrates (Han et al, 2018), although recent data indicate that the latter should be re-evaluated (Berheim et al, 2019;Eng et al, 2019;Wu et al, 2020).…”

“…Although recent estimates of use rates on these crops are not publicly available (the United States Geological Survey discontinued estimates in 2015), we know these compounds are used on virtually every hectare of corn planted in the United States, and that the amount of active ingredient applied to corn seeds doubled between 2011 and 2014 (Tooker et al, 2017). There are also high rates of use on seeds of soybeans, cotton and many other crop species (Douglas et al, 2015(Douglas et al, , 2020. It is important to note that these trends have been documented even as transgenic hybrids-Bt corn and cotton-have increasingly dominated the market, successfully reducing outbreaks of key pests of these crops (Dively et al, 2018) and even decreasing regional pest populations (Hutchison et al, 2010;Bohnenblust et al, 2014).…”

Time-Cumulative Toxicity of Neonicotinoids: Experimental Evidence and Implications for Environmental Risk Assessments

“…As neonicotinoids have replaced older pesticide chemistries in most countries, the actual toxic loads of insecticides per area have dramatically increased in recent years [86,87]. It is not surprising, therefore, that current declines of biodiversity have been linked to pesticides in both terrestrial [88] and aquatic environments [89][90][91], among which neonicotinoids are prevalent.…”