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Increasingly frequent warm periods during winter, which are associated with climate change, may cause mismatches between the colony phenology of the western honey bee, Apis mellifera L., and their floral resources. Warmer winter periods can also affect colony brood rearing activity and consequently the reproduction of the invasive brood parasite Varroa destructor Anderson and Trueman. Until now little is known about the effects of climate change on biotic interactions in such a multitrophic system comprising flowering plants, a pollinator, and its parasite. We performed a reciprocal translocation experiment with honey bee colonies to simulate climate change-induced phenology shifts. Honey bee brood phenology was highly sensitive to environmental conditions in late winter. Colonies in which phenology was experimentally delayed had smaller worker populations in early spring and reduced amounts of stored honey during the following months. During summer, the varroa load in colonies with non-shifted phenology was three times higher than in colonies with delayed phenology. High varroa loads during summer were negatively correlated with worker population growth. Despite a remarkable resilience of colony development to phenology shifts, our results show that mismatches between the phenology of honey bee colonies and flowering plants can affect the build-up of resource stores. Further, an advanced onset of brood rearing activity after hibernation can reinforce the negative impact of the brood parasite V. destructor. We conclude that trade-offs between synchronisation with earlier flower phenology and prolonged brood phases with build-up of varroa populations might constrain the honey bees’capability to adapt to climate warming.

Beekeepers commonly supplement honey bee (Apis mellifera L.) colonies' nutrition with commercial pollen and nectar substitutes in an effort to encourage growth and reduce colony losses. However, there is a broad lack of understanding regarding the extent to which supplemental protein feeding affects honey bee colony health. We conducted a field study to determine if feeding protein substitutes affected colony strength and Nosema spp. spore intensity in commercially managed honey bee colonies. Seventy-five honey bee colonies were randomly assigned to one of six treatments (no supplemental protein, one of four commercially available protein supplements, or wildflower pollen supplement).The number of adult bees, the number of capped brood cells, and Nosema intensity were assessed prior to-, 4 wk post-, and 8 wk post-treatment. There was an overall decrease in Nosema intensity across all treatments over time. However, there were no statistically detectable differences in colony strength or Nosema intensity between any of the pollen feeding treatments and those of the negative control treatment. Thus far, multiple investigations regarding supplemental protein feeding have failed to provide a clear consensus on the impact that this practice has on honey bee colony strength or productivity. Additional research is needed to determine the impact, if any, that diet supplementation, including microbial and nutritional supplements, has on colony health, to better inform beekeepers' management decisions.

Managed honey bees are the most important commercial pollinators of those crops which depend on animal pollination for reproduction and which account for 35% of the global food production. Hence, they are vital for an economic, sustainable agriculture and for food security. In addition, honey bees also pollinate a variety of wild flowers and, therefore, contribute to the biodiversity of many ecosystems. Honey and other hive products are, at least economically and ecologically rather, by-products of beekeeping. Due to this outstanding role of honey bees, severe and inexplicable honey bee colony losses, which have been reported recently to be steadily increasing, have attracted much attention and stimulated many research activities. Although the phenomenon “decline of honey bees” is far from being finally solved, consensus exists that pests and pathogens are the single most important cause of otherwise inexplicable colony losses. This review will focus on selected bee pathogens and parasites which have been demonstrated to be involved in colony losses in different regions of the world and which, therefore, are considered current threats to honey bees and beekeeping.

A honey bee colony is characterized by high genetic diversity among its workers, generated by high levels of multiple mating by its queen. Few clear benefits of this genetic diversity are known. Here we show that brood nest temperatures in genetically diverse colonies (i.e., those sired by several males) tend to be more stable than in genetically uniform ones (i.e., those sired by one male). One reason this increased stability arises is because genetically determined diversity in workers' temperature response thresholds modulates the hive-ventilating behavior of individual workers, preventing excessive colony-level responses to temperature fluctuations.

The honey bee parasite Varroa destructor Anderson & Trueman can disperse and invade honey bee colonies by attaching to “drifting” and “robbing” honey bees that move into nonnatal colonies. We quantified the weekly invasion rates and the subsequent mite population growth from the end of July to November 2011 in 28 honey bee colonies kept in two apiaries that had high (HBD) and low (LBD) densities of neighboring colonies. At each apiary, half (seven) of the colonies were continuously treated with acaricides to kill all Varroa mites and thereby determine the invasion rates. The other group of colonies was only treated before the beginning of the experiment and then left untreated to record Varroa population growth until a final treatment in November. The numbers of bees and brood cells of all colonies were estimated according to the Liebefeld evaluation method. The invasion rates varied among individual colonies but revealed highly significant differences between the study sites. The average invasion rate per colony over the entire 3.5-mo period ranged from 266 to 1,171 mites at the HBD site compared with only 72 to 248 mites at the LBD apiary. In the untreated colonies, the Varroa population reached an average final infestation in November of 2,082 mites per colony (HBD) and 340 mites per colony (LBD). All colonies survived the winter; however, the higher infested colonies lost about three times more bees compared with the lower infested colonies. Therefore, mite invasion and late-year population growth must be considered more carefully for future treatment concepts in temperate regions.

Sixteen honey bee (Apis mellifera L.) colonies were placed in four different agricultural landscapes to study the effects of agricultural landscape and exposure to pesticides on honey bee health. Colonies were located in three different agricultural areas with varying levels of agricultural intensity (AG areas) and one nonagricultural area (NAG area). Colonies were monitored for their performance and productivity for one year by measuring colony weight changes, brood production, and colony thermoregulation. Palynological and chemical analyses were conducted on the trapped pollen collected from each colony and location. Our results indicate that the landscape's composition significantly affected honey bee colony performance and development. Colony weight and brood production were significantly greater in AG areas compared to the NAG area. Better colony thermoregulation in AG areas' colonies was also observed. The quantities of pesticides measured in the trapped pollen were relatively low compared to their acute toxicity. Unexplained queen and colony losses were recorded in the AG areas, while colony losses because of starvation were observed in the NAG area. Our results indicate that landscape with high urban activity enhances honey bee brood production, with no significant effects on colony weight gain. Our study indicates that agricultural crops provide a valuable resource for honey bee colonies, but there is a trade-off with an increased risk of exposure to pesticides.

Several insect pheromones are multifunctional and have both releaser and primer effects. In honey bees (Apis mellifera), the queen mandibular pheromone (QMP) and e-beta-ocimene (eβ), emitted by young worker larvae, have such dual effects. There is increasing evidence that these multifunctional pheromones profoundly shape honey bee colony dynamics by influencing cooperative brood care, a fundamental aspect of eusocial insect behavior. Both QMP and eβ have been shown to affect worker physiology and behavior, but it has not yet been determined if these two key pheromones have interactive effects on hypopharyngeal gland (HPG) development, actively used in caring of larvae, and ovary activation, a component of worker reproductive physiology. Experimental results demonstrate that both QMP and eβ significantly suppress ovary activation compared to controls but that the larval pheromone is more effective than QMP. The underlying reproductive anatomy (total ovarioles) of workers influenced HPG development and ovary activation, so that worker bees with more ovarioles were less responsive to suppression of ovary activation by QMP. These bees were more likely to develop their HPG and have activated ovaries in the presence of eβ, providing additional links between nursing and reproductive physiology in support of the reproductive ground plan hypothesis.

Detection and interpretation of chemical cues is essential for Varroa destructor Anderson and Trueman, an important parasite of honey bees (Apis mellifera L.), to complete its life cycle. We collected volatiles from honey bee brood at various developmental stages and screened for V. destructor electrophysiological responses to these with gas chromatography-linked electrotarsal detection. Volatile collections contained several methyl-alkanes that evoked electrophysiological responses from V. destructor. Moreover, odors in honey bee colonies that regulate honey bee colony structure and function were also detected by V. destructor. Collections from mid- to late-stage larvae had detectable levels of low-volatility odors identified as components of the honey bee brood pheromone and branched alkanes likely originating from brood cuticle. Among these, several mid- to heavy-molecular weight compounds elicited high proportional electrophysiological responses by V. destructor relative to their abundance but could not be identified using chemical standards of previously documented honey bee brood odors. We suggest further investigation of these unknown volatiles and future behavioral assays to determine attractiveness/repellency (valence) of those identified through chemical standards.

Flupyradifurone (Sivanto) is a novel systemic insecticide from the butenolide class developed by Bayer. Based on available data (USEPA 2014), this insecticide appears to have a favorable safety profile for honey bee colonies. As a result, the label permits the product to be applied during prebloom and bloom in various crops, including citrus, except when mixed with azole fungicides during the blooming period. We placed 24 honey bee (Apis mellifera L.) colonies adjacent to eight flowering buckwheat (Fagopyrum esculentum Moench) fields that either had been sprayed with the maximum label rate of flupyradifurone or with water only (control fields), with three colonies placed adjacent to each field. We conducted colony strength assessments during which the number of adult bees, eggs, uncapped brood cells, capped brood cells, food storage cells, and weights of honey supers and brood chambers were determined prior to, during, and after the flowering period. We also analyzed bee-collected pollen and nectar for flupyradifurone residues. Overall, there were no differences in any colony strength parameter for colonies placed at control and flupyradifurone-treated buckwheat fields. Residue analyses showed that pollen (x = 565.8 ppb) and nectar (x = 259.4 ppb) gathered by bees on fields treated with flupyradifurone contained significantly higher flupyradifurone residues than did bee bread and unprocessed nectar collected by bees from control fields (75% of samples

Journal Article

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