Bee populations declining in the United States, especially in the midwest

“Since at least the 1960’s it has been widely recognized that insecticide application can also negatively affect non-target species, including populations of insect pollinators [like bees] and natural enemies that serve to support crop production.” The development of neonicotinoid insecticides (insecticides chemically similar to nicotine) have made their effect more potent.

Featured article:

Douglas, M. R., Sponsler, D. B., Lonsdorf, E. V., & Grozinger, C. M. (2020). County-level analysis reveals a rapidly shifting landscape of insecticide hazard to honey bees (apis mellifera) on US farmland. Scientific Reports, 10(1), 797. [PDF] [Cited by]

“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.

Studies suggest recent and widespread declines in insect abundance, diversity, and range, and insecticide use has been identified as a likely contributor along with habitat loss, species introductions, and climate change. In the US, declines have been documented in populations of several wild bee species, butterflies in Ohio and lowland California, and the migratory monarch butterfly. Meanwhile, beekeepers sustain losses of >40% of their managed honey bee colonies annually.

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.”

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