Domestic gardens supply pollinators with valuable habitats, but the risk of exposure to pesticides has been little investigated. Artificial nesting shelters of a red mason bee species (Osmia bicornis) were placed in two suburban gardens and two commercial fruit orchards to determine the contamination of forage sources by pesticides. Larval pollen provisions were collected from a total of 14 nests. They consisted mainly of pollen from oaks (65–100% weight/sample), Brassicaceae (≤34% w/s) and fruit trees (≤1.6% w/s). Overall, 30 pesticides were detected and each sample contained a mixture of 11–21 pesticide residues. The pesticide residues were significantly lower in garden samples than in orchard samples. The difference was attributed mainly to the abundant fungicides pyrimethanil and boscalid, which were sprayed in fruit orchards and were present on average at 1004 ppb and 648 ppb in orchard samples, respectively. The results suggested that pollinators can benefit from domestic gardens by foraging from floral sources less contaminated by pesticides than in adjacent croplands.

Significant proportions of imidacloprid-olefin and imidacloprid-urea in green plant tissues were demonstrated. The greater imidacloprid supply increased the imidacloprid-olefin/imidacloprid molar ratio in the green plant tissues. The absence of imidacloprid-olefin in the root excluded its retransport from leaves. The similar imidacloprid/imidacloprid-urea ratios in the soil and root indicated that the root serves primarily for transporting these substances. © 2016 Society of Chemical Industry.

BACKGROUND Pesticides have often been linked to honey bee colony losses, which occur mainly over winter. In this study, we investigated residues in nine colonies at a model agricultural research site during the period before wintering. Moreover, we applied the acaricide tau‐fluvalinate to the colonies via a strip formulation. The pesticide content was determined by UHPLC‐QqQ‐MS/MS in bees from brood comb initially collected in mid‐September immediately prior to the start of tau‐fluvalinate treatment and 30 later at the time of tau‐fluvalinate strip removal. RESULTS In addition to commonly analyzed pesticides, we detected two plant growth regulators, chlormequat and metazachlor, in the bee colonies. Whereas thiacloprid, chlormequat and acetamiprid decreased after 30 days and contributed considerably to differences between sample time points, other pesticides appeared to be rather stable. Interestingly, we identified diazinon, which has been banned in the European Union since 2007. The residues of methiocarb sulfoxide and imidacloprid‐urea in the absence of their parent compounds indicate historical environmental contamination that can be identified by the detection of residues in a bee colony. tau‐Fluvalinate was detected only after the 30‐day treatment at an average (± SD) concentration of 1.29 ± 1.93 ng/bee, ranging from 0.06 to 7.13 ng/bee. CONCLUSION The multidimensional behavior of pesticides in a bee colony was indicated. Although the research area is used for agriculture, the measured pesticide level was relatively low. The recorded concentrations of tau‐fluvalinate should not be dangerous to bees, as the values were ∼ 200–5000‐fold lower than the reported median lethal dose (LD50) values. © 2019 Society of Chemical Industry

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