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Two groups of eight honey bee colonies were fed with two different concentrations of imidacloprid in saccharose syrup during summer (each colony was given 1 litre of saccharose syrup containing 0.5 microg litre(-1) or 5 microg litre(-1) of imidacloprid on 13 occasions). Their development and survival were followed in parallel with control hives (unfed or fed with saccharose syrup) until the end of the following winter. The parameters followed were: adult bee activity (number of bee entering the hive and pollen carrying activity), adult bee population level, capped brood area, frequency of parasitic and other diseases, mortality, number of frames with brood after wintering and a global score of colonies after wintering. The only parameters linked to feeding with imidacloprid-supplemented saccharose syrup when compared with feeding with non-supplemented syrup were: a statistically non-significant higher activity index of adult bees, a significantly higher frequency of pollen carrying during the feeding period and a larger number of capped brood cells. When imidacloprid was no longer applied, activity and pollen carrying were re-established at a similar level for all groups. Repeated feeding with syrup supplemented with imidacloprid did not provoke any immediate or any delayed mortality before, during or following the next winter, whereas such severe effects are described by several French bee keepers as a consequence of imidacloprid use for seed dressing in neighbouring cultures. In any case, during the whole study, mortality was very low in all groups, with no difference between imidacloprid-fed and control colonies. Further research should now address several hypotheses: the troubles described by bee keepers have causes other than imidacloprid; if such troubles are really due to this insecticide, they may only be observed either when bees consume contaminated pollen, when no other sources of food are available, in the presence of synergic factors (that still need to be identified), with some particular races of bees or when colonies are not strong and healthy.

International audienceTetracyclines are used to control bacterial diseases like European and American foulbrood which may cause severe losses in honey bee population and honey production. This study, using 24 hives randomly distributed into four groups of 6 hives, was performed for measuring the occurrence of tetracycline (TC) residue levels in honey following two types of TC application. Two groups of colonies were treated 3 times with 0.5 g of TC in 1 litre of syrup (group S) or in 10 g of powdered sugar (group P). Six hives of a first control group (group C) fed with untreated syrup were installed at 20 and 45 metres from groups S and P respectively. A second control group (group DC) was disposed 3 km apart. TC residues in honey sampled at different times in all hives and in honey artificially contaminated with TC and stored in the laboratory at 4, 20 and 35°C were analysed by ELISA and HPLC methods. One day after the last application, the mean TC concentration in brood chamber honey was ten times higher in group S (40.7 mg.kg-1) than in group P (4.34 mg.kg-1). After 8 days, TC residues were detected in all hives of group C. After 146 days, the mean TC concentration in harvested honey was 1.54, 0.35, and 0.15 mg.kg-1 for groups S, P and C respectively. The control group C had been contaminated by drifting. In all hives of the group DC, no residues were detected at any time of the study. The honey harvested at day 504 did not contained any detectable TC residues, except in one super from group C (0.026 mg.kg-1). The half-life time of TC in honey from supers was similar in groups C, S and P and equal to 65 days. This duration was twice lower than in honey stored in laboratory in similar conditions : at 35°C in the dark (t1/2 = 121 days). In honey stored at 20°C, TC was quite stable as its half-life time was 242 days. The data from these experiments specify levels of TC residues in honey after a treatment in hives, their persistence and diffusion into the apiary. These results show that the TC must be used with precaution in honey production

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