Monitoring in-hive residues of neonicotinoids in relation to bee health status

Abstract

A field study was done to search for residues of neonicotinoids in twelve honeybee hives in four apiaries in the corn and soybean growing area of southern Ontario, in Canada, and to determine if any bee loss or symptoms of stress were associated with such residues. Dead bees in front of the hive, and live forager bees at the hive entrance and inside the hive were collected. Pollen, honey and nectar were also sampled. Acetamiprid, clothianidin and thiamethoxam and the metabolite TZNG were included in the analysis, and extensive diagnostic tests were done to monitor mites and diseases. Clothianidin, thiamethoxam and TZNG were found in dead bees collected in front of the hives and forager bees from the hive entrance but not in bees from inside the hive. The concentrations found in bees and hive products were below the NOELs for bees, and were not associated with any evidence of stress or bee loss. Mite levels were low, but viruses were frequently found. The pattern of distribution of residues was parallel to what has been reported for other chemicals including chlorpyrifos. Implications of this pattern for the role of the eusocial behaviour of bees in allowing a bee colony to forage on plants bearing natural or xenobiotic toxins are discussed.

Keywords: honeybee, colony loss, virus, neonicotinoid, resistance