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

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.

In silico identification and assessment of insecticide target sites in the genome of the small hive beetle, Aethina tumida

“…Evaluating the sensitivity of small hive beetle to these compounds may present an opportunity for selective control. Other insecticides that act at the cys-loop ligand-gated ion channels such as spinosad, fipronil, and avermectin are extremely toxic to honey bees [32,83,84]. Selectivity for SHB with these compounds is likely to be based on differences in spatial exposure rather than physiological differences in the target sites for these compounds, as observed in the effectiveness of Apithor® traps that are impregnated with fipronil for SHB control [14,85].…”

Biological control of leaf‐cutter ants using pathogenic fungi: experimental laboratory and field studies

“…The traditional and most effective method of controlling LCAs has been chemical pesticides, the most efficient being those applied in the form of baits (De Britto et al., 2016). However, all ant pesticides are completely banned or in the process of being removed from the market (e.g., organochlorines, organophosphates, and sulfluramid) due to the enormous negative effects that they cause (Stockholm Convention, 2009; De Britto et al., 2016; FSC, 2019), including mortality to natural enemies (e.g., Guillade & Folgarait, 2014a), to bees (e.g., Li et al., 2010), or toxicity in water and soil (e.g., Hayasaka et al., 2012), not to mention the impact on human health (e.g., Vilela, 1986). Therefore, there is an urgent need for alternative strategies, among which biological control agents (BCAs) – especially those using microorganisms – are the most promising so far (Shah & Pell, 2003).…”

Potential of some soil amendments in reducing leaching of fipronil to groundwater

“…Besides this, it also acts as a slow poison and provides a serious threat to aquaculture as it is highly toxic to fish, aquatic invertebrates, etc. (Stehr et al 2006;Li et al 2010).…”