Dietary quercetin impacts the concentration of pesticides in honey bees
Graphical abstract
Introduction
The detrimental effect of pesticides on bee health is a topic of global concern. Bees provide a fundamental pollination service in ecosystems, and declines in their populations will have serious ecological and economic consequences (Goulson et al., 2008). Declining bee populations could lead to a pollination crisis and reduce crop yields (Holden, 2006; Goulson et al., 2015). Honey bees (Apis mellifera L.) are considered the most important pollinators due to both their efficiency and omnipresence (Winfree et al., 2011; Codling et al., 2016). Since 2007, colony collapse disorder (CCD) has impacted honey bee colonies in many parts of the world (Underwood and Vanengelsdorp, 2007; Vanengelsdorp et al., 2009). Proposed explanations for the observed cases of CCD include multiple stressors, such as reduced food availability, decreased flower diversity, parasites, modern beekeeping practices, and continuous agrochemical exposure (Goulson et al., 2015). Focus has often been on honey bee exposure to different classes of pesticides during foraging. Neonicotinoids are the most extensively used systemic insecticides worldwide due to their efficacy against a wide range of crop pests (Sánchez-Bayo, 2014). Neonicotinoids have commonly been used as seed coatings, in soil applications, and in foliar applications on agricultural crops such as oilseeds, grains, fruits, vegetables and on ornamental plants, many of which are attractive to honey bees (Codling et al., 2016; Jiang et al., 2018). Thus, honey bees consume imidacloprid during their foraging. In 2018, the EU banned the three main neonicotinoids (clothianidin, imidacloprid, and thiamethoxam) for outdoor use on plants visited by honey bees. Once exposed to imidacloprid, honey bees are quickly immobilized; however, within 24 h, they recover due to their continuous metabolism of imidacloprid (Schott et al., 2017). Imidacloprid is more toxic to honey bees when they digest it compared to when they are contact-exposed to it (EFSA, 2018). Tebuconazole, an ergosterol biosynthesis inhibitor (EBI) in the triazole fungicide group, is heavily used in Europe and may spread to flowering wild plants (EFSA, 2008; David et al., 2016). In a study in the UK, tebuconazole was found at concentrations up to 73 ng/g in all oilseed pollen samples taken (David et al., 2016). Tebuconazole was reported to be the most frequent fungicide in beeswax samples in Uruguay (Harriet et al., 2017). Tau-fluvalinate is an insecticide used as an in-hive acaricide (Mullin et al., 2010) to control the Varroa mite, which is a serious and devastating ectoparasite in honey bee colonies (Francis et al., 2013). Thus, honey bees are regularly subjected to tau-fluvalinate in their hives. Its low acute toxicity to honey bees means that acute tau-fluvalinate poisoning is rare. Tau-fluvalinate and tebuconazole have low toxicity (LD50 = 12 μg/bee and >200 μg/bee, respectively) to honey bees, but investigation of the mechanisms contributing to acaricide and fungicide metabolization is essential to determine synergistic and antagonistic interactions with natural xenobiotics (EFSA, 2008, 2010).
The flavonol quercetin, an abundant phytochemical in pollen, is an intrinsic part of the honey bee diet. Daily rates of quercetin ingestion depend on the floral sources of pollen and nectar that honey bees consume. Consumption of quercetin-sucrose paste (10 mg quercetin/g) can reduce the acute toxicity of tau-fluvalinate in honey bees (Johnson et al., 2012) and increase their longevity in the presence of pyrethroids (Liao et al., 2017). Cytochrome P450s (CYPs) are a large group of enzymes that contribute to the detoxification of xenobiotics in insects (Dulbecco et al., 2018). The CYP9Q sub-family (CYP9Q1, CYP9Q2, and CYP9Q3) metabolizes imidacloprid as well as phytochemicals (Mao et al., 2011; Liao et al., 2017). Dietary quercetin upregulated P450 genes and triazole fungicide mycobutanil disturbed the metabolization pathway of quercetin (Mao et al., 2017). Thus, we hypothesized that consumption of quercetin alters the concentrations of imidacloprid and tau-fluvalinate while concentrations of tebuconazole will not be affected by dietary quercetin in honey bees (Fig. 1). The aim of this study was to quantify the effect of adding quercetin to honey bee diets on the concentration of three pesticides which honey bees are inadvertently exposed to: an insecticide (imidacloprid), a fungicide (tebuconazole), and an acaricide (tau-fluvalinate). The results of this study determine whether the exploitation of plants with high concentrations of quercetin in their pollen should be recommended as supplementary fodder in beekeeping.
Section snippets
Chemicals and preparation of reagents
Imidacloprid (98% purity), tebuconazole (99.3% purity), tau-fluvalinate (91.2% purity), quercetin (95% purity), ammonium formate (99% purity), and sucrose (99.5% purity) were purchased from Sigma-Aldrich (Steinheim, Germany). Acetic acid was purchased from Fisher Scientific (Leicestershire, UK). Formic acid was purchased from Merck (Darmstadt, Germany). Methanol (HPLC grade), acetonitrile (HPLC grade), and acetone were purchased from Rathburn (Walkerburn, UK). Bond Elut QuEChERS dispersive kits
Recovery, precision, LOD and LOQ
The percent recoveries, LODs and LOQs of the pesticides are shown in Table 2. The obtained percent recoveries were within the range (60–140%) recommended by the EU guidelines and ranged from 72% with an RSD of 22% for imidacloprid, 92% with an RSD of 7.3% for tebuconazole and 105% with an RSD of 12% for tau-fluvalinate (SANTE/11,813/2017, 2017).
The LODs and LOQs were below 3.6 and 12.1 ng/g, respectively (Table 2). The lowest and highest limits were achieved for tau-fluvalinate (LOD: 2.4 ng/g;
Conclusions
The results support the hypothesis that quercetin increases the metabolization of imidacloprid. Accelerated turnover of imidacloprid reduces exposure to toxic compounds. However, our results illustrate that dietary quercetin cannot significantly alter the concentrations of tebuconazole or tau-fluvalinate in honey bees. The obtained results demonstrated that exposing honey bees to tebuconazole enabled them to metabolize quercetin more efficiently. Importantly, our findings provide additional
Credit authorship contribution statement
Hamidreza Ardalani: Data curation, Formal analysis, Investigation, Validation, Visualization, Writing - original draft. Nanna Hjort Vidkjær: Data curation, Investigation, Methodology, Conceptualization, Supervision, Writing- Reviewing and Editing, Funding acquisition. Bente B. Laursen: Data curation. Per Kryger: Methodology, Conceptualization, Supervision, Writing- Reviewing and Editing. Inge S. Fomsgaard: Methodology, Conceptualization, Supervision, Writing- Reviewing and Editing, Funding
Funding
This study was funded by a project (27060) at the Graduate School of Science and Technology, Aarhus University (GSST, AU), Denmark.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
We would like to thank GSST, AU, for financial support and Kirsten Heinrichson and Elena-Claudia Jensen for technical support.
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2022, Science of the Total EnvironmentCitation Excerpt :The harmful impacts of poor nutrition on bee health have also been repeatedly demonstrated through field studies and complementary laboratory studies of captive bees (Tasei and Aupinel, 2008; Di Pasquale et al., 2013; Brunner et al., 2014; Cane, 2016; Costa et al., 2020). Studies on the interactions between pesticides and nutrition have primarily been performed in the well-studied western honey bee Apis mellifera, where pollen diet composition appears to reduce sensitivity to some pesticides (Schmehl et al., 2014; Ardalani et al., 2021a, 2021b; Barascou et al., 2021). Pollen diets can vary considerably in nutrient content and concentrations (Roulston T’ai and Cane, 2000) and in secondary metabolites (Palmer-Young et al., 2018); consequently, unique pollen diets might mediate pesticide effects on bees differently.