Toxicities of fipronil enantiomers to the honeybee Apis mellifera L. and enantiomeric compositions of fipronil in honey plant flowers

Authors

  • Xiqing Li,

    Corresponding author
    1. Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871 People's Republic of China
    • Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871 People's Republic of China.
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  • Chen Bao,

    1. Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871 People's Republic of China
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  • Daibin Yang,

    1. Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100094 People's Republic of China
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  • Mingqi Zheng,

    1. Department of Applied Chemistry, China Agricultural University, Beijing, 100094 People's Republic of China
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  • Xuefeng Li,

    1. Department of Applied Chemistry, China Agricultural University, Beijing, 100094 People's Republic of China
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  • Shu Tao

    1. Laboratory of Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871 People's Republic of China
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Abstract

Fipronil is a chiral phenylpyrazole insecticide that is effective for control of a wide range of agricultural and domestic pests at low application rates. Wide application of fipronil also causes poisoning of some nontarget insects, such as honeybees. In the present study, toxicities of fipronil enantiomers and racemate to the honeybee Apis mellifera L. were determined to examine whether using formulations of single or enriched fipronil enantiomer is a possible option to reduce risks to bees. Contact toxicity tests yielded median lethal doses (LD50) of 3.45, 3.38, and 3.86 ng/bee for the R(−)-enantiomer, S(+)-enantiomer, and racemate, respectively. Analysis of variance indicates that the LD50 values are not statistically different (p = 0.41). Oral toxicities of the R-enantiomer, S-enantiomer, and racemate (nominal median lethal concentration = 0.037, 0.045, 0.053 mg/L, respectively) were also demonstrated to be not statistically different (p = 0.20). In addition, enantiomeric fractions of fipronil in the flowers of three honey plants (Brassica campestris, Cucumis sativus, and Chrysanthemum indicum L.) were examined after treatment with fipronil. It was found that degradation of fipronil in all three plants is not enantioselective. These results indicate that it is unlikely that use of formulations with single or enriched fipronil enantiomer would reduce the risk that fipronil poses to honeybees. Improved fipronil application practices (based on safest timing and bloom conditions) and reduction of overall fipronil usage seem to be more realistic options. Environ. Toxicol. Chem. 2010;29:127–132. © 2009 SETAC

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