Search

Identifying traits for adaptation to different management and environmental regimes is key to maintaining robust honey bee populations under global climate change. We compared mite-resistant (Pol-line and Russian) and Italian honey bee stocks in variable-temperature cage experiments (200 bees per cage) with respect to food consumption, thermoregulation, gene expression, and lifespan, in 3 experiments over 2 years. The Italian stock bees consumed more syrup and pollen on average than the mite-resistant stocks, but the mite-resistant stocks maintained higher cluster temperatures and had median lifespans 8 days longer, consistent with the increased expression of vitellogenin relative to Italian stock. Model results indicated that, to maintain the same colony size as the mite-resistant stocks, Italian stock colonies would need about 13% more sealed brood to offset reduced worker lifespans. These differences among bee stocks likely influence colony-level productivity and health, and showed the importance of experimental replication. [ABSTRACT FROM AUTHOR]

Internal temperatures of honey bee hives kept at different sites in North Dakota were monitored before and during winter to evaluate the effects of treatment, in the form of exposure to commercial pollination, and location on colony health. In October, hives exposed to commercial pollination during the summer had fewer adult bees and less brood than hives kept near natural forage, as well as lower average temperatures throughout winter. Within-day temperature variability was higher among hives exposed to commercial agriculture than for those kept near natural forage, indicating reduced temperature control. Fungicides, insecticides, varroacides, and an herbicide were detected in bee bread and wax samples; no major differences were observed either in the diversity or in the concentrations of agrochemicals with the exception of chlorpyrifos at one site. Varroa and Nosema densities were low overall. Data from the same site used in successive years showed significantly more brood the first year, as well as lower temperature variability; high levels of chlorpyrifos were detected in bee bread of colonies in the second year. Colony average temperature and temperature variability were informative with respect to colony phenology and post-winter status. [ABSTRACT FROM AUTHOR]

CO2, a byproduct of respiration, is toxic at high concentrations so regulation of CO2 within the honey bee hive is an important colony function. In this study, we measured hive CO2 concentrations at 1-s intervals while ventilation characteristics of the hive were changed every few days, and we analyzed the data for effects of increased ventilation on colony behavior and thermoregulation. Average CO2 concentrations were significantly higher, by > 200 ppm, when hives had screened bottom boards (higher ventilation) compared to hives with solid bottom boards (lower ventilation) at the same time. Daily CO2 concentration amplitudes, hourly temperature, daily temperature amplitudes, nor hourly hive weight changes were not significantly affected by the changes in hive ventilation. In a second experiment, we found average CO2 concentrations at the top center of the upper hive box, on top of the frames, were significantly lower than concentrations at the center of a solid bottom board underneath frames, which was expected due to the higher density of CO2 relative to air. Bee colonies have been reported to cycle air, with shorter periods of 20 to 150 s and longer periods of 42–80 min, but a periodogram analysis of the CO2 concentration data found no evidence of important CO2 cycle periods other than a strong 24-h period. Bee colonies maintained strong daily cycles of CO2 concentration, with average maximum concentrations > 11,000 ppm, even in conditions of increased ventilation, indicating that managing CO2 concentration is a complex colony behavior. [ABSTRACT FROM AUTHOR]

Survivorship, syrup consumption, and cluster temperatures of honey bees were kept in hoarding cages with different numbers of bees. Cages with either 50, 100, 150, or 200 bees each were monitored over 4-6 weeks in incubators with 12h/12h 30° C/15° C temperature cycles to induce clustering. Survivorship and syrup consumption rates per bee were not different among the bee density groups, but cluster temperatures were. Cluster temperatures ranged from 0.45°C above incubator temperature in the 50 bee cages to 4.05° C in the 200 bee cages over the 1st 7 days, with each additional bee adding on average 0.02° C to cluster temperature. In another set of experiments, cages were established with about 200 bees each, and imidacloprid added to the syrup at 0, 5, 20, and 100 ppb. Imidacloprid in the syrup did not affect bee survivorship but it did reduce syrup consumption per bee, with bees fed 100 ppb imidacloprid syrup consuming on average 631 mg per bee over 28 days while average consumption among the other groups ranged from 853 to 914 mg. Cluster temperature was affected by imidacloprid treatment: bees fed 5 ppb imidacloprid syrup had higher cluster temperatures over the 1st 10 days, 4.17° C above incubator temperature, than either bees fed 100 ppb syrup or control (2.35 and 3.19° C, respectively). [ABSTRACT FROM AUTHOR]

Supplemental forage can be used to provide nutrition to bees during winter dearth. We examined the effects of supplemental forage on colony performance, colony survival, worker quality, and queen pheromone signaling in Nosema ceranae-infected overwintering colonies. Colonies were either supplemented with rapini or left unsupplemented for 1 month before almond pollination. Unsupplemented colonies experienced higher mortality than supplemented colonies. Supplemental forage did not affect colony performance, worker mass, or hypopharyngeal gland protein content. However, supplemented queens released more of three queen QMP and QRP compounds (4-hydroxy-3-methoxyphenylethanol, methyl oleate, and 1-hexadecanol) that promote queen care among workers. In addition, colonies that survived almond pollination thermoregulated their hives more than colonies that failed. Supplemental forage may prepare overwintering colonies for the stresses of early spring pollination. [ABSTRACT FROM AUTHOR]

The aim of the present work was to assess the effects of landscape and pesticides on honey bee survival and physiological stress. Integrated use of acetylcholinesterase and detoxification enzymes was tested on honey bee brains for detecting possible exposure to pesticides. Foragers were tracked in agricultural and non-agricultural landscapes in West Tennessee (USA) and then recovered for molecular and chemical analyses. In addition, four honey bee cohorts were fed imidacloprid in the laboratory ad libitum for several weeks and were analyzed by RT-qPCR for gene expression. Pesticides were identified at different concentrations in both crop flowers and recovered foragers. No significant differences in foragers' mortality were found among locations. Acetylcholinesterase and detoxification genes showed no response to exposure to pesticides except for GstS3 and GstS4. Our results suggest that none of the studied genes make suitable biomarkers for honey bee exposed to pesticides. [ABSTRACT FROM AUTHOR]