This recent USDA study was co-authored by Tom Rinderer & Robert Danka of the USDA-ARS Honey Bee Breeding, Genetics and Physiology Laboratory. Glyphosate ranks at the very bottom of the list of toxicity to honey bees


Twenty insecticides are highly toxic chemicals, including thiamethoxam, clothianidin, three organophosphates (acephate, chlorpyrifos, and dimethoate), and most pyrethroids tested. 

Ten pesticides are moderately toxic, including imidacloprid and a few carbamate insecticides. The remaining 11 pesticides are slightly toxic chemicals to honey bees, including acetamiprid, spiromesifan and novaluron. If LD50s (µg/g of active ingredient) are used for the classification, 33 pesticides would fall into extremely toxic category. 

From this study, it is clear that tetraconazole (a fungicide), etoxazole (miticide), and glyphosate (a popular herbicide) have very minor or no acute toxicity to honey bees based on 48-h mortality data, with the results being supported by an additional week-long observation.

Zhu, Y. C., Adamczyk, J., Rinderer, T., Yao, J., Danka, R., Luttrell, R., & Gore, J. (2015). Spray toxicity and risk potential of 42 commonly used formulations of row crop pesticides to adult honey bees (Hymenoptera: Apidae). Journal of economic entomology

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