a type of fat that supports brain function, cell growth and heart health - may help protect honey bees against the toxic effects of pesticides, according to a study led by researchers at Penn State.
The study, published in the Journal of Insect Physiology, described the effects of diets rich in various fats - saturated, monounsaturated or polyunsaturated fatty acids - on bee survival after exposure to the pesticide chlorpyrifos.
The team found that bees fed a diet high in polyunsaturated fatty acids had a 90% survival rate after exposure to the pesticide, whereas fewer than 50% of bees fed diets high in saturated or monounsaturated fats survived.
Jaya Sravanthi Mokkapati, assistant research professor at Penn State and lead author on the paper, said the findings suggest that improving the quality - not just the quantity - of dietary fats, or lipids, available to bees could help strengthen their resilience to pesticide exposure.
"This could inform the development of supplementary diets for managed honey bees and the design of pollinator habitats containing plant species that provide pollen with beneficial fatty-acid profiles, particularly polyunsaturated fatty acids," she said. "However, these results come from a controlled laboratory study and should not be interpreted as suggesting that nutrition can replace efforts to reduce pesticide exposure."
Instead, Mokkapati added, nutritional support could serve as an additional protective strategy alongside reduced pesticide use, safer application practices and integrated pest management.
"Pesticides are a helpful tool for managing pests that threaten crops, but they also pose a threat to vital pollinators," said Christina Grozinger, Publius Vergilius Maro Professor of Entomology, director of the Huck Institutes of the Life Sciences and co-author on the paper. "While reducing exposure to these pesticides is important, it could also be helpful to develop strategies that help pollinators tolerate unavoidable exposure in agricultural landscapes."
Nutrition is one factor that could influence how well bees cope with pesticide stress, Mokkapati said. Previous studies from the Grozinger lab in the Center for Pollinator Research showed that specific protein-to-lipid ratios in the diet can affect pesticide tolerance in honey bees, but Mokkapati said much less was known about whether the specific type of dietary fat also matters.
"These questions are important because identifying nutrients that improve pesticide resilience could inform the design of pollinator-friendly habitats, floral plantings and supplementary diets," Mokkapati said. "Ultimately, improving the nutritional quality of the resources available to bees may provide a practical way to strengthen their resilience while broader efforts continue to reduce pesticide risks."
For the study, different groups of bees were fed a protein-based diet enriched with either saturated fatty acids, monounsaturated fatty acids or polyunsaturated fatty acids for five days. The bees also were fed either sucrose-only diets or protein-only diets without added fats alongside the fat-enriched diets.
"This allowed the bees to consume and assimilate the different dietary components before pesticide exposure," Mokkapati said.
For each diet, the cages were then divided into two treatment groups: an unexposed control group and a group exposed to chlorpyrifos, a pesticide used extensively in agriculture. The researchers then monitored food consumption and survival for another five days before analyzing different physiological markers in the surviving bees.
"We then measured the bees' abdominal energy reserves - carbohydrates, proteins and lipids - as well as glutathione-S-transferase activity, a detoxification enzyme that helps remove toxins from cells," Mokkapati said. "We also analyzed acetylcholinesterase activity, an important enzyme in the nervous system, to determine whether dietary fatty-acid composition influenced the bees' physiological responses and resilience to pesticide exposure."
The researchers found that bees consumed more of the monounsaturated fatty acid and polyunsaturated fatty acid diets than the saturated fatty acid diet, indicating a preference for unsaturated fats.
The polyunsaturated fatty acid diet also helped bees maintain greater reserves of lipids in their abdomens as well as higher acetylcholinesterase activity after chlorpyrifos exposure, suggesting the diet supported better energy balance and nervous system function under stress from the pesticide.
In contrast, glutathione-S-transferase activity was not significantly different among the three diets, suggesting that the protective effect of polyunsaturated fatty acids was not mainly driven by this detoxification pathway.
It's important to note, Mokkapati said, that the chlorpyrifos concentration used in the study was substantially higher than residue levels generally reported in honey bee foraging areas and should be considered a laboratory challenge dose rather than a realistic approximation of what a honey bee would encounter naturally.
"In agricultural landscapes, bees are more likely to encounter lower concentrations of multiple pesticides, together with other stressors such as poor nutrition, pathogens, parasites and temperature extremes," she said. "Future studies could examine whether the protective effects of polyunsaturated fatty acids are maintained under environmentally relevant concentrations, pesticide mixtures, and combinations of nutritional and environmental stressors."
This research was supported by the Human Frontier Science Program under grant number RGP0057/2021, the United States Department of Agriculture's National Institute of Food and Agriculture Federal Appropriations under project number PEN04944 and accession number 7008085, the Publius Vergilius Maro Professorship, and Huck Institutes of the Life Sciences. This content is solely the responsibility of the authors and does not necessarily represent the official views of the funders.
