International audiencePollen resources may become a constraint for the honey bee in cereal farming agrosystems and thus influence honey bee colony development. This survey intended to increase knowledge on bee ecology in order to understand how farming systems can provide bee forage throughout the year. We conducted a 1-year study to investigate the flower range exploited in an agrarian environment in western France, the physico-chemical composition of honey bee-collected pollen, the territorial biodiversity visited by the bee at different periods, and the relationships between these three datasets. Palynological analyses showed the importance of maize among crop pollens and that of weeds during the food shortage period. Pollen protein varied from 16% to 29% and lipids from 7% to 24%. The contribution of different habitats to pollen harvest, was from crops (62%), woods (32%), grasslands (4%), and gardens (1%)

Thirty-two honeybee (Apis mellifera) colonies were studied in order to detect and measure potential in vivo effects of neonicotinoid pesticides used in cornfields (Zea mays spp) on honeybee health. Honeybee colonies were randomly split on four different agricultural cornfield areas located near Quebec City, Canada. Two locations contained cornfields treated with a seed-coated systemic neonicotinoid insecticide while the two others were organic cornfields used as control treatments. Hives were extensively monitored for their performance and health traits over a period of two years. Honeybee viruses (brood queen cell virus BQCV, deformed wing virus DWV, and Israeli acute paralysis virus IAPV) and the brain specific expression of a biomarker of host physiological stress, the Acetylcholinesterase gene AChE, were investigated using RT-qPCR. Liquid chromatography-mass spectrometry (LC-MS) was performed to detect pesticide residues in adult bees, honey, pollen, and corn flowers collected from the studied hives in each location. In addition, general hive conditions were assessed by monitoring colony weight and brood development. Neonicotinoids were only identified in corn flowers at low concentrations. However, honeybee colonies located in neonicotinoid treated cornfields expressed significantly higher pathogen infection than those located in untreated cornfields. AChE levels showed elevated levels among honeybees that collected corn pollen from treated fields. Positive correlations were recorded between pathogens and the treated locations. Our data suggests that neonicotinoids indirectly weaken honeybee health by inducing physiological stress and increasing pathogen loads.

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Caracterisation de signaux chimiques impliques dans les relations plantes-abeilles domestiques. (Characterization of chemicals involved in honeybee-plant interactions.)-Gnna 33: 184-190. ISSN To characterize plant chemicals cueing honeybees preferences between sunflower genotypes selected to produce hybrid seeds, combined behavioral and chemical analyses were undertaken. From observations of the foraging behavior under field conditions, bees' preferences between female and male parent lines were shown. Since bees' attraction to plants is based upon an associative conditioning between food, provided by nectar and pollen, and plant volatiles, these components were compared between genotypes. Sugar composition of nectars was analyzed by gas chromatography: glucose. fructose and sucrose were identified, with sucrose inducing bees' preferences. Pollen production was quantified on parent lines and resulting hybrid varieties, using a coulter-counter device. Differences among parent lines and heredity effect were found. However, there were strong interaction between parental lines and high variability within genotypes. Pollenkitt analysis using thin layer chromatography was undertaken to separate the main classes of lipids (hydrocarbons, sterols, mono-, di-and triglycerids). Fatty acids composition was analyzed by gas chromatography, the main components being two unsaturated fatty acids. Comparison of volatile components collected by air-entrainment method showed differences between male and female genotypes. Discriminative components were limited to 10% of the volatile blends and were identified by coupled gas chromatography-mass spectrometry.