title: Determination of exposure levels of honey bees foraging on flowers of mature citrus trees previously treated with imidacloprid.
abstract: BACKGROUND
  Field and tunnel cage studies were undertaken to determine the extent to which honey bees foraging on citrus blossoms were exposed to imidacloprid and its metabolites when citrus trees were treated with soil applications of the insecticide. Residues were measured by LC/MS/MS in nectar and pollen samples from trees treated up to 232 days prior to bloom.
  
  
  RESULTS
  Imidacloprid, imidacloprid olefin and 5-hydroxy imidacloprid were detected in nectar and pollen sampled from the flowers of citrus trees treated with imidacloprid up to 232 days prior to bloom. In tunnel studies, where foraging was restricted exclusively to citrus, imidacloprid residues in nectar extracted from flowers and from bee crops were similar (<10 ng mL(-1) ) and below the established no-observed-effects limit; however, the residue levels were about threefold higher in nectar sampled from comb. Concentrations of imidacloprid in nectar were higher in trees treated with higher application rates.
  
  
  CONCLUSIONS
  Imidacloprid and its metabolites were detected in the nectar and pollen of citrus trees treated up to 232 days prior to the onset of bloom. However, based on published bioassay data, the imidacloprid concentrations in the floral nectar did not surpass levels that would compromise foraging activity under normal use conditions for imidacloprid. Further research is needed to assess the impact of elevated levels of imidacloprid within stored nectar in the comb.
authors.affiliation: Department of Entomology, University of California, Riverside, CA, USA.
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Byrne
authors.forename: P Kirk
authors.initials: PK
authors.lastname: Visscher
authors.forename: Bill
authors.initials: B
authors.lastname: Leimkuehler
authors.forename: Dave
authors.initials: D
authors.lastname: Fischer
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Grafton-Cardwell
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Morse
mesh_terms: D000818:Animals; D001516:Bees / Q000737:chemistry* / Q000187:drug effects; D002957:Citrus / Q000737:chemistry* / Q000254:growth & development; D004781:Environmental Exposure / Q000032:analysis; D035264:Flowers / Q000737:chemistry* / Q000254:growth & development; D007093:Imidazoles / Q000032:analysis* / Q000633:toxicity; D007306:Insecticides / Q000032:analysis* / Q000633:toxicity; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000032:analysis* / Q000633:toxicity; D011058:Pollen / Q000737:chemistry; D053719:Tandem Mass Spectrometry
chemical_list: D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; C082359:imidacloprid
keywords: Apis mellifera ligustica; citrus; honey bees; imidacloprid; nectar