Evaluation and comparison of the effects of three insect growth regulators on honey bee queen oviposition and egg eclosion

Authors: Fine, Julia

Submitted to: Ecotoxicology and Environmental Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2020
Publication Date: 8/20/2020
Publication URL: https://handle.nal.usda.gov/10113/7081556
Citation: Fine, J.D. 2020. Evaluation and comparison of the effects of three insect growth regulators on honey bee queen oviposition and egg eclosion. Ecotoxicology and Environmental Safety. 205. https://doi.org/10.1016/j.ecoenv.2020.111142.
DOI: https://doi.org/10.1016/j.ecoenv.2020.111142

Interpretive Summary: Honey bees are highly valued pollinators that help to ensure national food security in the United States, but reports of heavy annual losses to managed colonies have caused concerns and prompted investigations into the causes of colony losses. One of the major players that negatively affects honey bee health and survival is agrochemical exposure. Investigations into the sublethal effects of agrochemicals on important metrics of colony health such as reproduction and queen health has been limited by the availability of targeted methods to study honey bee queens. Here, we investigate the effects of three insect growth regulators (IGR), a class of agrochemicals known to affect aspects of insect reproduction, on honey bee queen oviposition, egg hatching, and worker hypopharyngeal development in order to quantify their effects on the fecundity of mated queens. Our results demonstrate that none of the IGRs affected oviposition, but all three affected egg hatching. Worker bees consuming methoxyfenozide had significantly larger hypopharyngeal glands at two weeks of age than bees not fed this compound. The results suggest that although IGRs may not exhibit direct toxic effects on adult honey bees, they can affect larval eclosion from eggs and the physiology of workers, which may contribute to colony population declines over time.

Technical Abstract: Honey bees (Apis mellifera) are highly valued pollinators that help to ensure national food security in the United States, but reports of heavy annual losses to managed colonies have caused concerns and prompted investigations into the causes of colony losses. One of the major players that negatively affects honey bee health and survival is agrochemical exposure. Investigations into the sublethal effects of agrochemicals on important metrics of colony health such as reproduction and queen fecundity has been limited by the availability of targeted methods to study honey bee queens. Here, we investigate the effects of three insect growth regulators (IGR), a class of agrochemicals known to target pathways involved in insect reproduction, on honey bee queen oviposition, egg hatching, and worker hypopharyngeal development in order to quantify their effects on the fecundity of mated queens. Our results demonstrate that none of the IGRs affected oviposition, but all three affected egg eclosion. Worker bees consuming methoxyfenozide had significantly larger hypopharyngeal glands at two weeks of age than bees not fed this compound. The results suggest that although IGRs may not exhibit direct toxic effects on adult honey bees, they can affect larval eclosion from eggs and the physiology of workers, which may contribute to colony population declines over time.