Commercial Bumble Bee Colonies Research Articles

Identification of fungi isolated from commercial bumblebee colonies.

Fungi can have important beneficial and detrimental effects on animals, yet our understanding of the diversity and function of most bee-associated fungi is poor. Over 2 million bumblebee colonies are traded globally every year, but the presence and transport of viable fungi within them is unknown. Here, we explored whether any culturable fungi could be isolated from commercial bumblebee nests. We collected samples of various substrates from within 14 bumblebee colonies, including the honey, honey cup wall, egg cup wall, and frass then placed them on agar and recorded any growth. Fungal morphotypes were then subcultured and their ITS region sequenced for identification. Overall, we cultured 11 fungal species from the various nest substrates. These included both pathogenic and non-pathogenic fungi, such as Aspergillus sp., Penicillium sp., and Candida sp. Our results provide the first insights into the diversity of viable fungal communities in commercial bumblebee nests. Further research is needed to determine if these fungi are unique to commercial colonies or prevalent in wild bumblebee nests, and crucially to determine the ecological and evolutionary implications of these fungi in host colonies.

Observations on the Foraging Behaviors of Commercial Bumble Bee Colonies in Prunus avium Orchards

Prunus avium blooming period starts in early spring. The uncertain climatic conditions in this period can cause mis-pollination syndromes. It could be directly because of the frozen days or non-forgeable conditions for the possible pollinators or indirectly the poor quality of surrounding habitat and lack of pollinators. When wild pollinators are scarce owing to one of these reasons, introduction of commercial pollinators can be a solution to ensure pollination. Within this context, commercial bombus colonies were chosen as insurance for the pollination of sweet cherries. In the blooming period of Prunus avium, for two years-with totally 120 transect observations, the daily foraging activities of these bumblebees were investigated in Sultandağı-Afyonkarahisar. Before the settlement of the hives in the field, trees were marked with different colored stripes every 10 meters which makes it possible to follow how far the bumblebees fly and forage in the field. Starting at 7:00, 9:00, 11:00, 14:00, 16:00, and 18:00, six times a day, with transect observations, the number of the foragers on cherries was recorded. The average number of flowers they visit per minute was calculated. The plants blooming simultaneously with cherry trees in the trial area were determined. Pollen preferences of foragers were examined with their cobicular pollen loads. The actual foraging range was found as 10-40 meters away from the hives, the maximum activities were recorded before the noon. The average number of visited flowers per minute for bumblebees was ~ 8 flowers. Taraxacum spp. and Lamium spp. pollen were found, but cherry preference was determined to be almost 90%. It is still an uncommon agricultural practice to use commercial bumble bees in open fields, especially for the plants which have very early blooming periods in early spring, it is thought that they are very good manageable pollinator agents according to their foraging capacities.

The effect of sunflower pollen age and origin on pathogen infection in the common eastern bumble bee (Apidae: Hymenoptera).

Bumble bees are globally important pollinators, contributing hundreds of millions of dollars annually in crop pollination services. Several species are in decline, making it paramount to understand how pathogens and nutrition shape bee health. Previous work has shown that consuming sunflower pollen (Helianthus annuus) dramatically reduces infection by the trypanosomatid gut pathogen, Crithidia bombi, in the common eastern bumble bee (Bombus impatiens). Sunflower pollen may therefore be useful as a dietary supplement for reducing this pathogen in managed bumble bee colonies. Here, we assessed the efficacy of freezer-stored sunflower pollen that was collected in different years and locations for reducing pathogen infection. We tested sunflower pollen that was 1, 3, 4, or 5 yr old and from sunflowers grown in the United States or China against a control of 1-yr-old buckwheat pollen from China, since buckwheat pollen results in high infection. We hypothesized that older pollen would have weaker medicinal effects due to degradation of pollen quality. We found that all sunflower pollen treatments significantly decreased Crithidia infection compared to controls. These results suggest that sunflower pollen can be freezer-stored for up to 5 yr and sourced from a wide range of geographic areas and still maintain its medicinal effects against Crithidia in the common eastern bumble bee. This is helpful information for stakeholders who might administer sunflower pollen as a dietary supplement to manage Crithidia in commercial bumble bee colonies.

Simple and farmer-friendly bumblebee conservation: Straw bales as nest sites in agricultural landscapes

Many bumblebee species are declining due to a loss of semi-natural habitats in agricultural landscapes resulting in diminished forage and nest sites. Anecdotal experience indicates that bumblebees nest in straw bales, but scientific evidence is lacking. We spent 250 h screening for bumblebee nests in 1255 straw bales and ten straw stacks belonging to 58 farms in two intensively farmed Swedish regions and recorded nests, nest traffic, and straw characteristics. We supplemented the straw screening with screening of control areas, without straw, that were selected in similar environments as the areas with straw. We observed 45 bumblebee nests (including potential nests where a single bumblebee flew in or out of the straw) of eight species/species groups, including one red-listed, in or directly adjacent to the straw at 26 of the farms. Nests were mainly found in partly decayed straw and bales placed together. We found no nests in control areas. Based on our results, we suggest that straw can be used as an easy, cheap and efficient intervention to increase the availability of bumblebee nest sites in agricultural landscapes. Considering the costs and benefits of the alternatives, we conclude that straw addition has advantages over commercial bumblebee colonies for crop pollination purposes and over artificial nest boxes for conservation purposes.

Genomic divergence and a lack of recent introgression between commercial and wild bumblebees (Bombus terrestris).

The global movement of bees for agricultural pollination services can affect local pollinator populations via hybridization. When commercial bumblebees are of the same species but of different geographic origin, intraspecific hybridization may result in beneficial integration of new genetic variation, or alternatively may disrupt locally adapted gene complexes. However, neither the existence nor the extent of genomic introgression and evolutionary divergence between wild and commercial bumblebees is fully understood. We obtained whole‐genome sequencing data from wild and commercial Bombus terrestris collected from sites in Southern Sweden with and without long‐term use of commercially imported B. terrestris. We search for evidence of introgression, dispersal and genome‐wide differentiation in a comparative genomic analysis of wild and commercial bumblebees. Commercial B. terrestris were found in natural environments near sites where commercial bumblebees were used, as well as drifting wild B. terrestris in commercial bumblebee colonies. However, we found no evidence for widespread, recent genomic introgression of commercial B. terrestris into local wild conspecific populations. We found that wild B. terrestris had significantly higher nucleotide diversity (Nei's pi, π), while the number of segregating sites (Watterson's theta, θw) was higher in commercial B. terrestris. A highly divergent region on chromosome 11 was identified in commercial B. terrestris and found to be enriched with structural variants. The genes present in this region are involved in flight muscle contraction and structure and pathogen immune response, providing evidence for differing evolutionary processes operating in wild and commercial B. terrestris. We did not find evidence for recent introgression, suggesting that co‐occurring commercial B. terrestris have not disrupted evolutionary processes in wild B. terrestris populations.

Genetic and Usurpation Data Support High Incidence of Bumble Bee Nest Invasion by Socially Parasitic Bumble Bee, Bombus insularis.

Cuckoo bumble bees (Psithyrus) (Lepeletier, 1832) (Hymenoptera: Apidae) are a unique lineage of bees that depend exclusively on a host bumble bee species to provide nesting material, nutritional resources, and labor to rear offspring. In this study, we document usurpation incidence and population genetic data of Bombus insularis (Smith, 1861) (Hymenoptera: Apidae), a bumble bee species in the Psithyrus subgenus, on field-deployed B. huntii colonies in northern Utah, United States. Within 12 d of deploying B. huntii Greene, 1860 (Hymenoptera: Apidae) colonies at two field sites, 13 of the 16 colonies contained at least one established B. insularis female. Although our results demonstrate that field-deployed bumble bee colonies are highly susceptible to B. insularis usurpation, applying a fabricated excluder to prevent the inquiline from invading a colony was 100% effective. Sibship analysis using microsatellite genotype data of 59 B. insularis females estimates that they originated from at least 49 unique colonies. Furthermore, sibship analysis found siblings distributed between the field sites that were 7.04 km apart. Our result suggests that B. insularis females have the capacity to disperse across the landscape in search of host colonies at distances of at least 3.52 km and up to 7.04 km. Our study underscores the detrimental impact B. insularis usurpation has on the host bumble bee colony. As B. insularis significantly impacts the success of bumble bee colonies, we briefly discuss how the utilization of excluders may be useful for commercial bumble bee colonies that are used to pollinate open field crops.

No detectable impact of parasite-infected commercial bumblebees on wild bees in areas adjacent to greenhouses despite diet overlap

Over two million commercial bumblebee colonies are used on an annual basis to pollinate around 20 crop types worldwide. Despite their use, especially with crops grown in greenhouses, there is mounting evidence that many individuals also forage outside of them. Hence, the use of commercial bumblebees poses a risk to wild pollinators, especially to those who share floral resources and pathogens. To date, however, there is little evidence about the impact of commercial bumblebees on pollinator communities in Europe. We surveyed the abundance of commercial Bombus terrestris and the prevalence of four of its parasites in natural areas at increasing distances from vegetable crops in Cabo de Gata-Níjar (Almería, SE Spain), the most extensive greenhouse cultivation area in the world. We also estimated resource niche overlap (i.e., shared plants used) between commercial bumblebees and the native pollinator community. Finally, we explored whether the abundance and diversity of pollinators in natural habitats were influenced by agricultural expansion (i.e., distance to greenhouses) and bumblebee abundance. We found a sharp reduction in commercial bumblebee densities at increasing distances from greenhouses, with most bumblebees (95%) foraging within a radius of less than 200 m from them. However, these commercial bumblebees had high parasite prevalence (41% of individuals infected) of trypanosomatids, microsporidians and neogregarines. Moreover, their diet particularly overlapped with honeybees and large wild bees. Yet, pollinator density and diversity were not related to the distance from greenhouses or to bumblebee abundance. Although our results suggest that commercial bumblebees do not significantly harm wild pollinators, actions like preventing their escape from greenhouses, monitoring their health and optimising their use should be considered so as to minimise future risks.

Growth Characteristics of Commercial Bumblebee Colonies in Open Field Conditions May Be Evidence for Their Invasion Potential

Growth Characteristics of Commercial Bumblebee Colonies in Open Field Conditions May Be Evidence for Their Invasion Potential

The potential for parasite spill-back from commercial bumblebee colonies: a neglected threat to wild bees?

Commercially-reared bumblebee colonies provide pollination services to numerous crop species globally. These colonies may harbour parasites which can spill-over to wild bee species. However, the potential for parasites to spread from wild to commercial bumblebees, which could then lead to parasite spill-back, is poorly understood. To investigate this, parasite-free commercial Bombus terrestris audax colonies, which are used commercially for strawberry pollination, were placed into seasonal strawberry crops for either 6- or 8-week blocks across two key time periods, early spring and early summer. Bumblebees were removed from colonies weekly and screened for the presence of parasites. In the early spring placement, only one parasite, the highly virulent neogregarine Apicystis bombi, was detected at a low prevalence (0.46% across all bees screened). In contrast, all colonies placed in the crop in the early summer became infected. A trypanosome, Crithidia bombi, and A. bombi were the most prevalent parasites across all samples, reaching peak prevalence in screened bees of 39.39% and 18.18% respectively at the end of the experimental period. The prevalence of A. bombi was greater than most UK records from wild bumblebees, suggesting that commercial colonies could enhance levels of A. bombi infection in wild bees through spill-back. Studies on larger geographical scales with different commercial colony densities are required to fully assess spill-back risk. However, seasonal management, to minimise spill-back opportunities, and treatment of commercial colonies to prevent infection, could be implemented to manage the potential risks of parasite spill-back to wild bees.Implications for insect conservation Our results show that commercial bumblebee populations do pick up infections, most likely from wild bees, and that these infections can reach prevalences where they may pose a threat to wild bees via parasite spill-back. More research is required to clarify the extent of this potential threat.

Annual flowers strips benefit bumble bee colony growth and reproduction

Bumble bees are important crop pollinators but are negatively impacted by agricultural intensification and concomitant loss of floral resources. Flower strips can increase the abundance and sometimes the diversity of bumble bees at local scales, but the importance of flower strips for bumble bee populations at larger scales remains poorly understood. We investigated the effect of flower strips on bumble bee colony growth and reproduction at landscape scales. Commercial bumble bee colonies of a native species (Bombus terrestris) were placed and monitored at different distances from flower strips that were sown on existing ecological focus areas (European Common Agricultural Policy) in southern Sweden. Both the average colony growth (weight) and the production of reproductives (drones and queens) were highest for colonies adjacent to flower strips and declined with increasing distance. Colonies close to the flower strip also produced more reproductives per colony weight. Colony foraging activity was negatively related to the distance to flower strips whereas worker size was not affected. Annual flower strips in ecological focus areas benefit bumble bee colonies by increasing foraging success, colony growth and finally boosting sexual reproduction, demonstrating potential benefits for pollination within and between seasons. These effects were spatially limited but extended to foraging ranges of bumble bees. However, effects of increased colony growth on the abundance of foraging bees in the landscape may extend to larger distances because of forager movements within seasons and queen dispersal between seasons, suggesting that voluntary or incentivised collaboration between farmers may be needed to achieve optimal implementation of flower strips.

Seasonality of bumblebee spillover between strawberry crops and adjacent pinewoods

In agricultural landscapes, differences in floral resources provided by crops compared with adjacent habitats promote the spillover of pollinators seeking to fulfil their feeding needs. These foraging patterns play an important role in both crop production and wild plant fitness. However, in classical observational studies, pollinator spillover patterns may be confounded by differences in pollinator phenologies and population sizes. To avoid these confounding effects, we quantified the combined effect of relative floral availability and season on pollinator spillover between strawberry crops and adjacent pinewoods by using commercial bumblebee colonies. We used 60 colonies that were placed in 6 open polytunnel strawberry crops and in 8 pinewoods adjacent to crops in landscapes with either low or high berry (mostly strawberry) crop cover. We repeated the experiment in winter and in spring to account for differences in flower resource availability. While strawberries were in bloom during the entire study period, wild flowering plants were scarce and abundant in winter and in spring, respectively. Spillover in crops was quantified as the percentage of bumblebee individuals that carried pollen from non-berry flowers, while spillover in pinewoods was quantified as the percentage of individuals that carried pollen from berry flowers. Overall, 526 bumblebees were collected. We found them carrying the pollen of 15 plant taxa in winter and 39 in spring, in accordance with seasonal floral availability. In crop colonies, around 30% of bumblebees spilled over into non-berry habitats in winter and 78% in spring, regardless of crop cover in the surrounding landscape. However, in pinewood colonies, we found an interaction effect between season and crop cover: even though on average 34% of bumblebees spilled over into berry crops, in winter it was almost twice in landscapes with high crop cover. Spillover patterns mainly mirrored seasonal changes in floral availability between habitats.

Safeguarding the genetic integrity of native pollinators requires stronger regulations on commercial lines

Abstract Every year more than 1 million commercial bumblebee colonies are deployed in greenhouses worldwide for their pollination services. While commercial pollinators have been an enormous benefit for crop production, their use is emerging as an important threat. Commercial pollinators have been linked to pathogen spillover, and their introduction outside their native area has had devastating effects on native pollinators. A more pervasive but underappreciated threat is their potential impact on the genetic integrity of native pollinators. We set up a sampling and genotyping‐plus‐phenotyping protocol to evaluate the presence and extent of hybridization between commercial and native individuals of Bombus terrestris in south‐western Spain, a region experiencing a huge propagule pressure of non‐native genotypes due to the massive use of commercial colonies for crop pollination. Our genomic data show clear evidence of generalized hybridization between native and introduced commercial bumblebee lineages in southern Spain. Only 19% of analysed individuals were assigned with high confidence to the pure native genetic cluster and >45% of sampled specimens were first‐generation hybrids or backcrosses between native and commercial genotypes, indicating that genetic introgression is pervasive in southern Spain. Although the frequency of commercial genotypes sharply declined with the distance to greenhouses, non‐native alleles have introgressed into native populations inhabiting protected natural parks >60 km away from commercial bumblebee release areas. As pollination services demand will increase in the coming years, only a more restrictive regulation of commercial lines could mitigate their negative impacts on the genetic integrity of native pollinators, avoid processes of genetic homogenization, and prevent the potential disruption of local adaptations.

Managed bumble bees increase flower visitation but not fruit weight in polytunnel strawberry crops

Animal-mediated pollination is essential for the production and quality of fruits and seeds of many crops consumed by humans. However, crop pollination services might be compromised when wild pollinators are scarce. Managed pollinators are commonly used in crops to supplement such services with the assumption that they will enhance crop yield. However, information on the spatiotemporal pollinator-dependence of crops is still limited. We assessed the contribution of commercial bumble bee colonies compared to the available pollinator community on strawberry (‘Fortuna’ variety) flower visitation and strawberry quality across a landscape gradient of agricultural intensification (i.e. polytunnel berry crop cover). We used colonies of bumble bees in winter and in spring, i.e. when few and most wild pollinators are in their flight period, respectively. The placement of colonies increased visits of bumble bees to strawberry flowers, especially in winter. The use of bumble bee colonies did not affect flower visitation by other insects, mainly honey bees, hoverflies and other Diptera. Flower visitation by both honey bees and wild insects did not vary between seasons and was unrelated to the landscape gradient of berry crop cover. Strawberries were of the highest quality (i.e. weight) when insect-mediated pollination was allowed, and their quality was positively related to wild flower visitors in winter but not in spring. However, increased visits to strawberry flowers by managed bumble bees and honey bees had no effect on strawberry weight. Our results suggest that the pollination services producing high quality strawberry fruits are provided by the flower visitor community present in the study region without the need to use managed bumble bees.

Busier bees: increasing nest traffic in commercial bumblebee colonies

Commercially-reared bumblebee colonies contribute to the pollination of crops globally. If the efficiency of commercial colonies at providing pollination services could be increased, it would have implications for agricultural outputs. Commercial colonies are sold with an internal nectar reservoir on which bees can forage from within the nest. Nectar stores in naturally-produced nectar pots of colonies can affect forager recruitment and activity outside the nest. Thus, it is possible that artificial nectar reservoirs could impact the foraging activity of colonies. To investigate this, commercial Bombus terrestris audax colonies were placed in a university parkland campus. Colonies were split into three treatment groups: those with (1) access to an unaltered nectar reservoir; (2) access to a diluted reservoir; and (3) no reservoir access. Foraging observations were made for all colonies over a 19-day period. The mass of each colony was measured and demographic data were collected. Colonies with diluted reservoirs had 131% and 39% more bees entering and leaving than colonies with no reservoir access and unaltered reservoirs respectively. Both treatments with access to a nectar reservoir gained more mass, had a higher proportion of pollen foraging bees, and had more workers, males, larvae and pupae, than colonies with no access to a reservoir. These results demonstrate that manipulating the availability and concentration of internal nectar reservoirs of commercial B. terrestris colonies significantly affects the number of bees entering and leaving the colony. Dilution of the nectar reservoir could be a strategy for increasing the pollination services commercial colonies provide to crops. Further research in commercial crops is required before such a strategy could be implemented on farms.

A field study examining the effects of exposure to neonicotinoid seed-treated corn on commercial bumble bee colonies.

Neonicotinoid insecticides have been studied as possible contributors to bumble bee declines in North America and Europe. This has potential significance in corn agro-ecosystems since this crop is frequently treated with neonicotinoids and dominates much of the agricultural landscape in North America and Europe where bumble bees and other pollinators are commonplace. We conducted an experiment where commercial bumble bee (Bombus impatiens) hives were placed during pollen shed next to corn (Zea mays) fields that were grown from "conventional" seed that was treated with neonicotinoids, or "organic" seed that was not treated with pesticides. Samples of pollen were collected from corn plants for neonicotinoid residue analysis, pollen types carried by worker bees returning to hives were determined, and in autumn hives were dissected to measure various endpoints that serve as markers of colony vigor. Clothianidin was detected (0.1-0.8ng/g) in pollen collected from all conventional fields, but was not detected in pollen from organic fields. Corn pollen was only rarely collected from bumble bee foragers and the vast majority of pollen was from wild plants around the corn fields. All hives appeared healthy and neonicotinoid seed treatments had no effect on any hive endpoints measured, except the number of workers, where significantly fewer workers were recovered from hives placed next to conventional fields (96±15 workers per hive) compared to organic fields (127±17 workers per hive). The results suggest that exposure during pollen shed to corn grown from neonicotinoid-treated shed poses low risk to B. impatiens.

Mite species inhabiting commercial bumblebee (Bombus terrestris) nests in Polish greenhouses

Nests of social insects are usually inhabited by various mite species that feed on pollen, other micro-arthropods or are parasitic. Well-known negative effects of worldwide economic importance are caused by mites parasitizing honeybee colonies. Lately, attention has focused on the endoparasitic mite Locustacarus buchneri that has been found in commercial bumblebees. However, little is known of other mites associated with commercial bumblebee nests. Transportation of commercial bumblebee colonies with unwanted residents may introduce foreign mite species to new localities. In this study, we assessed the prevalence and species composition of mites associated with commercial bumblebee nests and determined if the mites are foreign species for Poland and for Europe. The study was conducted on 37 commercial bumblebee nests from two companies (Dutch and Israeli), originating from two greenhouses in southern Poland, and on 20 commercial bumblebee colonies obtained directly from suppliers. The species composition and abundance of mites inhabiting commercial bumblebee nests were determined. Seven mite species from three families were found in nests after greenhouse exploitation. The predominant mite species was Tyrophagus putrescentiae (Acaridae) that was a 100-fold more numerous than representatives of the family Laelapidae (Hypoaspis marginepilosa, H. hyatti, H. bombicolens). Representatives of Parasitidae (Parasitellus fucorum, P. crinitus, P. ignotus) were least numerous. All identified mite species are common throughout Europe, foreign species were not found. Mites were not detected in nests obtained directly from suppliers. We conclude that probably bumblebee nests are invaded by local mite species during greenhouse exploitation.

Kodamaea ohmeri(Ascomycota: Saccharomycotina) presence in commercial Bombus impatiens Cresson and feral Bombus pensylvanicus DeGeer (Hymenoptera: Apidae) colonies

SummaryIn this study, eight commercial and three feral bumble bee (Bombus impatiens Cresson and Bombus pensyivanicus DeGeer respectively, Hymenoptera: Apidae) colonies were tested for the presence of Kodamaea ohmeri (Ascomycota: Saccharomycotina), a yeast known to attract small hive beetles (SHB) (Aethina tumida Murray, Coleoptera: Nitidulidae) to honey bee (Apis mellifera L., Hymenoptera: Apidae) colonies. Swabs of commercial bumble bee colonies and homogenates of bumble bee colony components (adults, brood, honey, pollen and wax) were plated on selective media. The resulting yeast isolates were compared to K ohmeri previously isolated from SHB. Yeasts were detected in all of the commercial bumble bee colony swab samples (n = 56) and a selected subsample was shown through molecular, chemical, and microbiological evidence to be K. ohmeri. For the second part of the study, feral bumble bee colonies were excavated and evaluated for the presence of any SHB life stage (none was found). Adult bees and swabs from the colonies were plated on selective media. Kodamaea ohmeri was isolated in all samples collected from the feral bumble bee colonies. The presence of K ohmeri in commercial and feral bumble bee colonies is of concern, as SHB, which harbour K ohmeri, are attracted to the volatiles produced by K ohmeri growing on bee collected pollen.

Impacts of non-native bumblebees in Western Europe and North America

The earliest deliberate introductions of bumblebees to areas outside of their native range occurred over 100 years ago. Transportation of bumblebees accelerated in the late 1980s following the development of techniques for mass rearing them, and their widespread adoption as the preferred pollinator for a range of glasshouse crops, primarily tomatoes. There is now a worldwide trade in one species, Bombus terrestris dalmatinus, originating from south east Europe. Within North America, which does not allow the importation of B. terrestris, the trade is primarily in Bombus impatiens. Trade in B. t. dalmatinus threatens the integrity of other subspecies within Europe, such as B. t. audax which is endemic to Britain and Ireland. However, there is a conspicuous absence of data as to whether B. t. dalmatinus has established in the wild outside its native range, and whether it interbreeds with native subspecies. Perhaps a more significant risk associated with trade in bumblebees is the accidental spread of parasites, and the subsequent risk that native bumblebee species may be exposed to parasites for which they have little resistance. There is circumstantial evidence that catastrophic declines of several North American bumblebee species may have been triggered by the accidental introduction of pathogens from Europe. Even if commercial bumblebee colonies are reared locally, the high densities at which they are kept mean that glasshouse nests are likely to act as reservoirs for spread of disease to wild bumblebee populations nearby. There is clearly the need for tight quarantining of bee colonies before transportation, and a moratorium should be placed on the transport of bumblebees in cases where native species suitable for commercial rearing are readily available.

Potential application of the bumblebee foraging recruitment pheromone for commercial greenhouse pollination

Commercial bumblebee colonies are important crop pollinators. Here we assess whether ap- plication of artificial foraging recruitment pheromone can increase foraging activity in Bombus terrestris colonies on a relevant timescale for commercial pollination. We measured bee traffic from the nest to a foraging arena, which is correlated with foraging activity under natural recruitment conditions. During continuous pheromone exposure bee traffic increased by 1.5 to 3.6 times, and this increase lasted up to 105 minute. Repeated 20 minute exposures of a colony to recruitment pheromone, with at least 30 minutes intermissions, triggered consistent traffic increases over a four week period. We conclude that artificial re- cruitment pheromone can reliably boost bee traffic leaving previously inactive colonies. This method could improve foraging activity and pollination in greenhouse colonies, especially young colonies reluctant to start foraging after introduction to the crop. artificial recruitment pheromone / Bombus terrestris / chemical communication / crop yield / foraging activity

Use of Honey Bees and Bumble Bees to Disseminate Trichoderma harzianum 1295-22 to Strawberries for Botrytis Control

Abstract The effectiveness of using honey bees and bumble bees to vector a commercial formulation of Trichoderma harzianum 1295-22 for the control of Botrytis cinerea on strawberries was evaluated from 1994 to 1997 in 2 strawberry fields at the New York State Agricultural Experiment Station in Geneva, New York and in 10 grower fields in eight counties of New York. Commercial bumble bee colonies were used to deliver the biocontrol agent in 1994 and 1995 and five-frame nuclear honey bee hives were used in 1995–1997. Each honey bee exiting the hive carried about 1 × 105 colony-forming units of T. harzianum, with the majority found on the bees' legs (58%). Flowers collected from the bee-delivered treatment generally had half the density of T. harzianum as those from the sprayed treatment. However, during the 4 years of this study, T. harzianum delivered by bumble bees or honey bees provided better Botrytis control than that applied as a spray. In addition, the bee-delivered T. harzianum provided the same or a better level of control of Botrytis as commercial fungicides applied at bloom. Strawberries collected from the bee-visited treatments averaged 22% more seeds and weighed between 26 and 40% more than berries in nonvisited treatments. The number of seeds per berry and berry weight were reduced by 7–12% in plots treated with fungicides and visited by bees, indicating that the use of some commercial fungicides at bloom may impact pollination and yield. Bee delivery of T. harzianum 1295-22 is a viable option for strawberry growers interested in controlling Botrytis with minimal fungicide use.