Honey bee immune response to sublethal concentrations of clothianidin goes beyond the macronutrients found in artificial diets

Authors: Lau, Pierre; Tundo, Giovanni-Pao; Caren, Joel; Zhang, Weiqiang; Zhu, Yu Cheng

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2025
Publication Date: 3/28/2025
Citation: Lau, P.W., Tundo, G., Caren, J.R., Zhang, W., Zhu, Y. 2025. Honey Bee Immune Response to Sublethal Concentrations of Clothianidin Goes Beyond the Macronutrients Found in Artificial Diets. Scientific Reports. https://doi.org/10.1038/s41598-025-94647-1.
DOI: https://doi.org/10.1038/s41598-025-94647-1

Interpretive Summary: Pesticides and poor nutrition are key factors that together can negatively affect bee health leading to colony decline. In regions with intensive agricultural landscapes, such as row crops in the mid-south regions of the United States, agrochemicals are indispensable, leading to elimination of diverse forage for bees and exposure to harmful chemicals meant to limit damage from crop pests. Here we tested the impacts of a commonly used seed treatment neonicotinoid, clothianidin (CLO), on honey bee health when bees are exposed to diets varying in nutritional quality. Our results show that the supplementing proteins in diets improves longevity and bees receiving natural pollen had higher expression and activity levels of the genes and enzymes linked to pesticide detoxification. In conclusion, macronutrients in artificial diets can help promote glandular development, but natural pollen, a complex mixture of micro- and macro-nutrients and phytochemicals, has a positive impact on honey bee tolerance to pesticide stress.

Technical Abstract: Honey bees often encounter a variety of stressors in their environment, including poor nutrition and pesticides. These stressors interact and can be exacerbated in heavily anthropized habitats such as large-scale agroecosystems. In this study, we examine how diets varying in macronutrient ratios can affect nurse bee susceptibility to pesticide stressors. We did so by orally exposing nurse bees to varying sublethal concentrations of clothianidin (CLO), a neonicotinoid insecticide known to have sublethal and lethal effects on honey bees, after newly emerged bees were given an artificial high protein diet, intermediate diet, high lipid diet, natural pollen diet, or no diet at all. We monitored bee longevity and assessed bee physiology, enzyme activity levels, and gene expression to determine if there were effects on nutrition and CLO on honey bee fitness. We found benefits to bee longevity, physiology, enzyme activity, and gene expression when having access to a pollen diet and no individual effect of sublethal 5ppb and 20ppb CLO treatments. In the absence of pesticide stressors or at low concentrations, bees given the higher protein, balanced diet, and pollen had better survivorship compared to bees given no diet or a high lipid diet. The artificial diets improved bee health, but not to the extent of natural pollen diets. In contrast to honey bees given pollen, the artificial diets did little to promote honey bee detoxification enzymes and genes. Honey bees given natural pollen had demonstrated higher upregulation of detoxification genes and enzyme activity related to pesticide metabolism, which may be linked to their lower susceptibility when exposed to higher concentrations of CLO. Our results suggest that macronutrients in artificial diets can help promote bee nutrient levels and glandular development, but other nutrients in pollen, such as phytochemicals, are more directly linked honey bee tolerance to pesticide stress.