Glossary
An examination of how herbicides, while not directly toxic to bees at field-relevant concentrations, devastate pollinator populations by eliminating the wildflowers and flowering weeds that provide essential nectar and pollen forage. The indirect harm of herbicides may rival or exceed the direct harm of insecticides.
Most herbicides do not directly poison bees. However, they destroy the plants that bees depend on for survival. When glyphosate or other broad-spectrum herbicides eliminate dandelions, clover, goldenrod, asters, and other native wildflowers from field margins, roadsides, and agricultural areas, they remove the nutritional foundation that sustains pollinator populations.
A 2016 study estimated that herbicide use in U.S. agriculture has eliminated approximately 60 percent of the milkweed plants in the Midwest, decimating monarch butterfly populations. Similar losses of diverse wildflower communities affect all pollinators, including honey bees, by creating vast areas of nutritional desert between managed crops.
Recent research has added direct-harm concerns about glyphosate. A 2018 study published in the Proceedings of the National Academy of Sciences found that glyphosate exposure disrupts the honey bee gut microbiome, reducing populations of beneficial Lactobacillus and Snodgrassella bacteria that protect bees from pathogens. This microbiome disruption increased susceptibility to Serratia marcescens infection.
The combination of indirect (forage destruction) and potential direct (microbiome disruption) effects makes glyphosate-based herbicides a significant concern for bee health. Beekeepers should be aware of herbicide applications in their bees' foraging range.
Different mechanisms, possibly comparable total impact. Insecticides kill bees directly. Herbicides destroy the food supply, causing slow starvation and nutritional stress across entire landscapes. The chronic, landscape-scale impact of herbicide-driven forage loss may affect more bees than acute insecticide kills.
At field-relevant concentrations, glyphosate does not cause acute bee mortality. However, research shows it disrupts the bee gut microbiome, potentially increasing disease susceptibility. The primary harm remains indirect: destruction of forage plants that bees depend on.
Plant pollinator forage gardens, support conservation programs that maintain wildflower habitat, advocate for pollinator-friendly herbicide management (reduced mowing and spraying of roadsides and field margins), and communicate with neighboring landowners about the importance of wildflower habitat.
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