Honeybee Density Research Articles

Effectiveness of honey bees in delivering the biocontrol agent Bacillus subtilis to blueberry flowers to suppress mummy berry disease

Abstract Honey bees are important pollinators of commercial blueberries in the southeastern United States, and blueberry producers often use supplemental bees to achieve adequate fruit set. However, honey bees also vector the plant pathogenic fungus Monilinia vaccinii-corymbosi which infects open blueberry flowers through the gynoecial pathway causing mummy berry disease. Here, we report the results of a 3-year field study to test the hypothesis that using bee hives equipped with dispensers containing the biocontrol product Serenade, a commercial formulation of the bacterium Bacillus subtilis which has shown activity against flower infection by M. vaccinii-corymbosi in laboratory experiments, can reduce mummy berry disease incidence when honey bees are used as pollinators in blueberries. Individual honey bees carried 5.1–6.4 × 10 5 colony-forming units (CFU) of B. subtilis when exiting hive-mounted dispensers with Serenade. On caged rabbiteye blueberry bushes in the field, population densities of B. subtilis vectored by honey bees reached a carrying capacity of 3 CFU per flower stigma within 2 days of exposure, and there was a highly significant non-linear relationship between B. subtilis populations per stigma and bee activity, expressed as number of legitimate flower visits per time interval per cage ( R = 0.6928, P n = 32). Honey bee density (1600 or 6400 individuals per 5.8-m 3 cage) and Serenade treatment (presence or absence of the product in hive-mounted dispensers) significantly ( P

Foraging patterns of managed honeybees and wild bee species in an arid African environment: ecology, biodiversity and competition

Investigations into the potential impacts of selectively managing Apis mellifera on pollination ecology were carried out in several sites in Tsavo National Park of southern Kenya, a typical arid African environment. Temperature alone contributed significantly to the foraging patterns of both managed honeybees and wild bee species within the acacia - commiphora community. Honeybees, vulnerable to heat stress, foraged earlier in the day than wild bee species. Foraging patterns of the latter ranged from oligolectic to broadly non-specialized. Floral biology and adaptations were also considered in the analysis of divergent foraging trends. Observations suggest that honeybees potentially out-compete highly specialized wild bee species for scarce seasonal floral resources. No evidence was found of direct interaction on abundant seasonal floral resources such as the mass synchronous flowering of Acacia spp. at current managed honeybee densities. Investigation of visitors revealed a high diversity of potential insect pollinators, particularly high in wild bee species (Apoidea) diversity. Suggestions for the improved management of honeybees in arid African environments include shading of hives, providing access to water with protection from predators, and cultivation of indigenous, nectariferous plants close to hive colonies.

Honey bee (Hymenoptera: Apidae) pollination of rabbiteye blueberry Vaccinium ashei var. 'Climax' is pollinator density-dependent.

In a 2-yr field study, mature orchard plants of rabbiteye blueberry (Vaccinium ashei Reade variety 'Climax'), plus potted pollenizers ('Premier') were caged with varying densities of honey bees (0, 400, 800, 1,600, 3,200, 6,400, or 12,800 bees plus open plot) during the bloom interval. The rate of legitimate flower visits tended to increase as bee density increased within a range of 400-6,400 bees; there were more legitimate visits in cages with 6,400 bees than in those with < or = 1,600 bees. Similarly, within a range of 400-6,400 bees there was a trend for a corresponding increase in fruit-set with means ranging from 25.0 to 79%. Fruit-set was higher in cages with 6,400 or 3,200 bees than in those with < or = 800 bees. Regression analyses showed that fruit-set increased linearly with the rate of legitimate bee visits. Mean weight of berries was unaffected by bee density but varied significantly between years. Within a range of 0-3,200 bees/cage the average seeds per berry tended to increase with increasing bee density; there were more seeds in open plots than in cages with 12,800 honey bees or < or = 1,600 bees. Sucrose content ranged from 12.1 to 16.7% and fruits tended to have more sugar in cages with lower bee densities. Speed of ripening tended to be higher in cages with higher bee densities. Earlier work has shown that the effectiveness of Apis mellifera L. as a pollinator of rabbiteye blueberry is variety-dependent. Our data indicate that the effectiveness of A. mellifera is also bee density-dependent.

SCALE-DEPENDENT EFFECTS OF LANDSCAPE CONTEXT ON THREE POLLINATOR GUILDS

Most ecological processes and interactions depend on scales much larger than a single habitat, and therefore it is important to link spatial patterns and ecological processes at a landscape scale. Here, we analyzed the effects of landscape context on the distribution of bees (Hymenoptera: Apoidea) at multiple spatial scales with respect to the following hypotheses: (1) Local abundance and diversity of bees increase with increasing proportion of the surrounding seminatural habitats. (2) Solitary wild bees, bumble bees, and honey bees respond to landscape context at different spatial scales. We selected 15 landscape sectors and determined the percentage of seminatural habitats and the diversity of habitat types at eight spatial scales (radius 250-3000 m) by field inspections and analyses of vegetation maps using two Geographic Information Systems. The percentage of semi- natural habitats varied between 1.4% and 28%. In the center of each landscape sector a patch of potted flowering plants (four perennial and two annual species) was placed in the same habitat type, a grassy field margin adjacent to cereal fields. In all, 865 wild bee individuals and 467 honey bees were observed and an additional 475 individuals were caught for species identification. Species richness and abundance of solitary wild bees showed a close positive correlation with the percentage of seminatural habitats at small scales up to 750 m, whereas bumble bees and honey bees did not respond to landscape context at these scales. In contrast, honey bees were correlated with landscape context at large scales. The densities of flower-visiting honey bees even increased with decreasing proportion of seminatural habitats at a radius of 3000 m. We are not aware of any empirical studies showing contrasting foraging patterns related to landscape context at different spatial scales. We conclude (1) that local landscape destruction affects solitary wild bees more than social bees, possibly changing mutualistic plant-pollinator and competitive wild bees- honey bees interactions and (2) that only analyses of multiple spatial scales may detect the importance of the landscape context for local pollinator communities.

Resource overlap and possible competition between honey bees and wild bees in central Europe.

Evidence for interspecific competition between honey bees and wild bees was studied on 15 calcareous grasslands with respect to: (1) foraging radius of honey bees, (2) overlap in resource use, and (3) possible honey bee effects on species richness and abundance of flower-visiting, ground-nesting and trap-nesting wild bees. The grasslands greatly differed in the number of honey bee colonies within a radius of 2 km and were surrounded by agricultural habitats. The number of flower-visiting honey bees on both potted mustard plants and small grassland patches declined with increasing distance from the nearest apiary and was almost zero at a distance of 1.5-2.0 km. Wild bees were observed visiting 57 plant species, whereas honey bees visited only 24 plant species. Percentage resource overlap between honey bees and wild bees was 45.5%, and Hurlbert's index of niche overlap was 3.1. In total, 1849 wild bees from 98 species were recorded on the calcareous grasslands. Neither species richness nor abundance of wild bees were negatively correlated with the density of honey bee colonies (within a radius of 2 km) or the density of flower-visiting honey bees per site. Abundance of flower- visiting wild bees was correlated only with the percentage cover of flowering plants. In 240 trap nests, 1292 bee nests with 6066 brood cells were found. Neither the number of bee species nor the number of brood cells per grassland was significantly correlated with the density of honey bees. Significant correlations were found only between the number of brood cells and the percentage cover of shrubs. The number of nest entrances of ground-nesting bees per square metre was not correlated with the density of honey bees but was negatively correlated with the cover of vegetation. Interspecific competition by honey bees for food resources was not shown to be a significant factor determining abundance and species richness of wild bees.

The introduced HoneybeeApis melliferaand the Precautionary Principle: reducing the conflict

For more than 20 years there has been conflict arising from different points of view concerning the role of the introduced honeybee. There is a strong prima facie argument, and some supporting evidence, that introduced honeybees are likely to adversely affect the environment. Some land management agencies have consequently adopted a policy of removal of hive honeybees from areas devoted primarily to conservation. On the other hand, some argue that the scientific evidence on the issue remains poor, point out the economic benefits that arise from the honeybee industry and suggest that removal of apiaries from such areas is unjustified. It is suggested in this paper that adoption of the Precautionary Principle could Significantly reduce this conflict. Instead of the focus being on obtaining definitive “proof” concerning possible impacts of honeybees, it could shift to finding ways to reduce the density of feral honeybees, and hence their impacts on both the natural environment and honeybees in hives. The foc...

Influence of the apetalous character in rape (Brassica napus) on the foraging behaviour of honeybees (Apis mellifera)

AbstractIn order to establish whether commercial hybrid seed production between apetalous and apetalous rapeseed lines could be developed through insect cross‐pollination, observations were made to compare the foraging behaviour of honeybees on both flower types with regard to their attractiveness. Number of flowers/m2 and nectar volumes, considered as important attractive factors, did not differ between the two lines but nectar sugar composition was slightly different. Honeybee density was significantly higher on the apetalous line when their foraging activity was rather high. Honeybees showed a considerable constancy to each flower type. Passages between both types were not very frequent. Nectar foraging behaviour, observed under cages, differed with the floral morphology. On the apetalous flowers, honeybees visited the two inner nectaries by crawling over the anthers and the stigma, while on the apetalous ones they often inserted their tongues between the sepals, thus having less contact with the reproductive organs. From these results, the honeybee efficiency in cross‐pollination between petalous and apetalous lines appears to be reduced.

How do honey bees ( Apis mellifera) fuel their water foraging flights?

Water foraging bees in a desert collect water up to 2 km from their colony, and have consistent crop filling and flight times. They leave their colony and arrive at the water source with ≤1 mg sugar in their crops, which they dilute at the water source by collecting about 40 μl of water. In 500 m flights back to the colony, radioisotope studies show they pass almost no crop contents to their midgut. If prevented from entering the colony for 15–36 min, they do pass about half of their crop contents to their midgut, probably when hemolymph sugar levels become very low. This water is rapidly absorbed from the midgut to hemolymph, and then is apparently rapidly excreted to the rectum via the Malpighian tubules and defecated. In this process the bee absorbs and excretes a volume of water at least as great as her entire hemolymph volume in a relatively short time (≤20 min). The return flights of water collecting bees are normally fueled from sugar reserves in the bees' bodies, and these reserves limit water collection to within a few kilometers of the colony. This limitation probably affects dispersal and density of honey bees in arid areas.

Effect of a Honey Bee (Hymenoptera: Apidae) Gradient on the Pollination and Yield of Lowbush Blueberry

The object of this study was to establish the relationship between a gradient of honey bees, Apis mellifera L., and fruit production of low bush blueberry, Vaccinium angustifolium Aiton and V. myrtilloides Michaux. Five hundred colonies of honey bees were grouped at one end of a blueberry culture, and pollinator counts as well as fruit sampling were made between 0.5 and 5.0 km from the hives, thus obtaining fruit production data from plots with many to no observed honey bees. Four parameters were estimated to assess blueberry production: seed set, fruit set, berry weight, and maturation rate. All parameters were significantly and positively correlated with an increase in the density of honey bees.

Flower Production and Honey Bee Density Effects on Meadowfoam See Yield

Meadowfoam (Limnanthes alba Hartw. ex Benth. subsp, alba cv. Mermaid) is protandrous and entomophilous. Flower number and phenology, stigma receptivity, and timely honey bee pollination are highly weather dependent and were hypothesized to cause seed yield variation. The objective of this field experiment was to use a synchrony index, which is an estimate of flower receptivity and pollination timing synchrony, to relate variation in seed yield to number of open flowers and foraging honey bee (Apis mellifera L.) density. Transparent floating crop‐cover and shade cloth were used to alter flower number and flower phenology. The soil type was Amity silt loam (fine‐silty, mixed, mesic Argiaquic Xeric Argialboll). Cumulated open flowers and cumulated foraging bee density were derived from daily counts of flowers and foraging honey bees, respectively. Flower receptivity for each day was estimated using maximum air temperature for that day. Number of receptive flowers for each day was multiplied by the number of foraging bees for that day and summed for the bloom period to form cumulated synchrony index. A multiple regression model (R2 = 0.47, P &lt; 0.001) indicated a linear positive association of seeds per flower with cumulated foraging bee density, and a quadratic negative (within the experiment range) association with cumulated open flowers. A simple linear regression explained 87% (P &lt; 0.001) of the variation in seed number per area by difference in cumulated synchrony index. This confirms the importance of pollination timing, foraging honey bee activity, and total number of flowers for achieving high seed and oil yields and emphasizes the need for careful managemenat nd monitoring of these variables.

DENSITY, DIVERSITY, AND EFFICIENCY OF POLLINATORS OF SAINFOIN, ONOBRYCHIS VICIAEFOLIA SCOP.

AbstractThe density and efficiency of bumble bees, honey bees, and alfalfa leafcutter bees on sainfoin, Onobrychis viciaefolia Scop., grown in southern Alberta were studied. Six species of bees were identified as pollinators, with alfalfa leafcutter bees comprising 56% of the observations, honey bees 40%, and bumble bees 4%. The density of flowers over the season can be described as curvilinear. The mean number of flowers per raceme decreased significantly over the season. The rate of foraging by pollinator species from flower to flower varied and is described by multiple regression models. Julian date, hour of day, and flower density are the independent variables. More than 90% of the bees visited three or fewer flowers per raceme when 60% of the racemes had three or more flowers available for pollination. The bees foraged on sainfoin for about 12 h per day and average bee density increased significantly with the corresponding flower density. A theoretical approach used to predict the bee populations required to pollinate varying flower densities shows that the required population of bumble bees is about two-thirds that of honey bees or alfalfa leafcutter bees. The observed populations of pollinators did not correspond well with the derived values, probably because multiple visits per flower are required for fertilization.

Measuring the Importance of Honeybees in Rape Seed Production

SummaryA method of measuring the effect of honeybees on a field of rapeseed (Brassica campestris) was tested. The density of honeybees in the field was significantly related to distance from an apiary. Other gradients in the field were investigated with cages that excluded honeybees, the cages being used to calculate correction factors to compensate for variations in yield due to parameters other than insect density. The results showed that the design was practicable, and indicated that higher densities increased both seed yield and oil content of seed. The method needs to be tested where a more pronounced density gradient can be obtained.

Honeybee pollination of sunflower cultivars Hysun 30 and Sunfola

In trials on an irrigated crop of hybrid sunflowers, (Helianthus annuus), cv. Hysun 30, in northern Victoria, plots where bees had access produced 11 % more seed than plots where bees and larger insects were excluded. Although some seed was set in cages by airborne pollination and self-pollination, honeybees increased seed set significantly. There was a slightly greater oil content in seed from open plots but no difference in weight of 1000 seeds or percentage germination. There was a 20% increase in the percentage of flowers that set seed in the open compared with enclosed plots. There was a 1362% increase in open-pollinated flowers that set seed compared with self-pollinated, but there was no difference between open-pollinated and open-pollinated supplemented by hand-pollination. The yield of seed from open plots of the so-called 'open-pollinated' cv. Sunfola was directly related to the honeybee density on the crop, expressed as ratio of bees to inflorescences. Honeybees were effective cross-pollinators of the sunflowers. Hysun 30 pollen was not attractive to bees and they tended to discard it. Colony strength declined while the bees worked the crop. The data suggest that a rate of one honeybee per plant during anthesis could optimize yields of set seed.

The Number of Colonies and the Density of Honeybees in Sunflower Fields in Relation to the Pollination of the Crop

AbstractFertilization in sunflower fields seems to be dependent on the density of honeybees visiting the crop. However, density of honeybees is influenced by the effect of competitor flora and also by other factors to a much greater degree than by the number of colonies moved to the field. Accordingly, establishing the necessity of moving colonies to or increasing the number of colonies on sunflower fields for sufficient pollination is advisable to be based on investigations concerning the actual density of honeybees on the crop in bloom.ZusammenfassungAnzahl der Bienenfamilien und die Bienendichte im Zusammenhang mit der Bestäubung von SonnenblumenfeldernDie Bestäubung der Sonnenblumenfelder ist von der Abundanz der das Feld besuchenden Bienen abhängig. Die Bienendichte wird durch eine Anzahl von Faktoren in höherem Maße beeinflußt als durch die Zahl der Bienenfamilien, die neben das Feld ausgesetzt sind. Infolgedessen ist es ratsam, nach der tatsächlichen Individuendichte der Bienen zu entscheiden, ob im Interesse der Bestäubung die Aussetzung von Bienenfamilien notwendig ist, d. h. ob die Zahl der Bienenfamilien in der Nähe der blühenden Sonnenblumenfelder erhöht werden muß.

Observations on the pollination of apple trees (Malus sylvestrisMill.)

Insect visitation and pollination of the apple tree varieties Granny Smith, Kidd's Orange Red, and Golden Delicious were studied during the blossoming period in the Henderson and Warkworth districts near Auckland. The only pollinating insects observed on the trees were honey bees and negligible numbers of Bombus terrestris Linn, and long-tongued bumble bees (unidentified). Fruit set was very low on Granny Smith apple trees caged to exclude bees. Although density of honey bees per 30,000 flowers was greater than was previously found in Nelson, percentage pollination of apple varieties studied was somewhat lower. Certain orchards might benefit if hives were brought in for pollination.

Observations on the pollination of Montgomery red clover (Trifolium pratenseL.)

Abstract Over two seasons, observations were made on the role of the honey bee and the bumble bee in the pollination of Montgomery red clover (Trifolium pratense L.) in the South Canterbury, Mackenzie Country, North Otago, and South Otago districts of New Zealand. Conclusions were as follows:- 1. Honey bees and bumble bees were the only insects of importance as pollinators. 2. For most crops studied honey bees appeared to be more important than bumble bees. 3. The short-tongued bumble bee (Bombus terrestris L.) was of much less value as a pollinator than were long-tongued bumble bees or honey bees. 4. Crops were pollinated as effectively by honey bees as by the two main species of long-tongued bumble bees. 5. In general, very low honey bee densities, expressed as bees per 10,000 flowers, were associated with heavy competition from other nectar sources. 6. Expressed as bees per 10,000 flowers, average concentrations of both honey bees and long-tongued bumble bees were significantly higher for crops with po...

Observations on the pollination of apple trees (Malus sylvestrisMill.)

Abstract Insect visitation and pollination of the apple tree varieties Granny Smith, Kidd's Orange Red, and Golden Delicious were studied during the blossoming period in the Henderson and Warkworth districts near Auckland. The only pollinating insects observed on the trees were honey bees and negligible numbers of Bombus terrestris Linn, and long-tongued bumble bees (unidentified). Fruit set was very low on Granny Smith apple trees caged to exclude bees. Although density of honey bees per 30,000 flowers was greater than was previously found in Nelson, percentage pollination of apple varieties studied was somewhat lower. Certain orchards might benefit if hives were brought in for pollination.

Observations on the pollination of lucerne (medicago sativalinn.)

Abstract Observations were made on the role of the honey bee and the bumble bee in the pollination of lucerne (Medicago sativa Linn.) in the North Canterbury, North Otago, Central Otago, and Blenheim districts of New Zealand over two seasons. The relation between tripping and lucerne pollination was also studied. 1. (a) Pollination of crops averaged only 10 per cent. 2. (b) Pollination by insects in the field is thought to be due to accidental tripping by nectar-collecting honey bees, and consistent tripping by bumble bees. No other insects appear to be important as pollinators. 3. (c) A cage experiment in which honey bees and bumble bees were excluded suggested that automatic tripping was of little importance, at least in the Lincoln and Blenheim areas. 4. (d) Greatly increased pollination occurred in cages with high honey bee densities. This increase is attributed to a higher tripping rate in the cages, as high bee densities in the field, where little tripping occurs, are not accompanied by increased po...

Observations on the role of the honey bee and bumble bee as pollinators of white clover (Trifolium repensLinn.) in the Timaru district and Mackenzie country

Abstract Observations on the role of the honey bee and the bumble bee in the pollination of white clover (Trifolium repens Linn.) were made in the Timaru District and Mackenzie Country of New Zealand over 2 seasons. Bumble bees were of no importance in the Timaru area, although they played an important part in the Mackenzie Country, where honey bee densities were frequently low, Other insects were apparently of no importance. No pollination occurred in cages which excluded bees. Abnorrnally high honey bee densities achieved in cages resulted in little or no increase in the degree of pollination over that occurring under field conditions, in the Timaru district. In this area, therefore, present bee density must be considered adequate for seed crop production.