Plant richness and blooming cover affect abundance of flower visitors and network structure in Colombian orchards

1. Pollination is essential to fruit production. How plant diversity and blooming events in and around orchards affect the pollinator community and the plant-flower-visitor network in neotropical systems remains largely unknown.
2. We surveyed the flower visitors in deciduous fruit trees and alternative blooming resources (other crops, hedgerows and weeds) in Colombia across 6 orchards over 12 months. We evaluated whether plant species richness and blooming cover influenced abundance and richness of flower visitors, as well as network-level connectance and specialization. We also assessed the role of alternative blooming resources for the flower visitors of deciduous fruit trees.
3. Overall, we found 66 taxa of flower visitors, 35 of which visited deciduous fruit trees. There was a greater abundance of flower visitors when there was higher richness of weedy species and greater blooming cover of deciduous fruit trees. Networks were less connected when there was lower crop and weedy species richness. Finally, flower visitor abundance and specialization increased when there were multiple hedgerow species in bloom with a high blooming cover.
4. We highlight the importance of maintaining alternative blooming resources in and around the orchards to support deciduous fruit tree pollinators and diversity in the plant flower-visitor network.

     

Relationships between wild bees,hoverflies and pollination success in apple orchards with different landscape contexts

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Pollination efficiency and foraging behaviour of honey bees and non‐Apis bees to sweet cherry

1. Crop pollination generally increases with pollinator diversity and wild pollinator visitation. To optimize crop pollination, it is necessary to investigate the pollination contribution of different pollinator species. In the present study, we examined this contribution of honey bees and non‐Apis bees (bumble bees, mason bees and other solitary bees) in sweet cherry.
2. We assessed the pollination efficiency (fruit set of flowers receiving only one visit) and foraging behaviour (flower visitation rate, probability of tree change, probability of row change and contact with the stigma) of honey bees and different types of non‐Apis bees.
3. Single visit pollination efficiency on sweet cherry was higher for both mason bees and solitary bees compared with bumble bees and honey bees. The different measures of foraging behaviour were variable among non‐Apis bees and honey bees. Adding to their high single visit efficiency, mason bees also visited significantly more flower per minute, and they had a high probability of tree change and a high probability to contact the stigma.
4. The results of the present study highlight the higher pollination performance of solitary bees and especially mason bees compared with bumble bees and honey bees. Management to support species with high pollination efficiency and effective foraging behaviour will promote crop pollination.

     

Pollinator shift to managed honeybees enhances reproductive output in a bumblebee-pollinated plant

Introduced honeybees have had a large impact on native ecosystems by disrupting native plant–pollinator interactions. However, little is known of the effect of honeybees on reproduction of bumblebee-pollinated plants. Seasonal displacement of native bumblebees by introduced honeybees (Apis mellifera and A. cerana) was observed in Pedicularis densispica, endemic to Hengduan Mountains, China, providing an opportunity for honeybee presence/absence comparisons. Five-year field surveys were conducted in one frequently disturbed population at Yila Pasture (YP). We compared pollination effectiveness (combinations of visitation rate, efficiency in pollen transfer, and potential geitonogamy) between native and introduced managed bees. The total visitation rate of native bees and subsequent reproductive output decreased progressively, but honeybee introduction resulted in at least twofold increase in visitation and 70 % increase in seed set. In general, native bumblebees, which have larger bodies and longer proboscises and spent more time probing single flowers, were more efficient than honeybees in terms of pollen removal and pollen deposition during first visits to virgin flowers. Compared with bumblebees, honeybees visited markedly fewer flowers in sequence within individual plants, potentially reducing geitonogamous pollination. Our data highlight that introduced honeybees can provide pollination service in terms of both quantity and quality for P. densispica. We suggest honeybee introduction as an effective way to augment pollination of P. densispica at disturbed and isolated sites.     

Nesting activity of cavity-nesting bees and wasps is lower in small-scale apple orchards compared to nearby semi-natural habitats

1. Commercially reared cavity-nesting bees have been studied mainly in large, intensively managed orchards. However, knowledge on wild cavity-nesting bee and wasp communities and their potential limitations in smaller orchards remain insufficient.
2. We compared the colonization rate of trapnests, nesting success, parasitism and response to flower resources of cavity-nesting bees and wasps between apple orchards and nearby semi-natural habitats (SNHs).
3. Trapnests were placed in orchards and neighbouring SNHs. Colonization dynamics were studied and herbaceous flower resources were estimated. Furthermore, nest and brood cell quantity, number of alive offspring and nest parasitism rate were assessed.
4. We found a higher colonization rate in the SNHs than in the orchards. Both bees and wasps made more nests, completed more brood cells and had a higher number of alive offspring in the SNHs. The number of bee nests in the orchards showed a positive correlation with the species richness of the flowering plants. The nest parasitism of wasps was higher in the SNHs.
5. Apple orchards in the studied small-scale system were generally less colonized by cavity-nesting hymenopterans than nearby SNHs that can be important reservoirs of these ecosystem service provider hymenopterans. Our results highlight the importance of diverse flowering herbaceous vegetation in the understory that increased the number of bee nests in orchards and that could have a positive effect on the nesting activity of the bee species active in summer. Therefore, management practices that support flowering plant species in the understory vegetation are highly recommended in such orchards.

     

Characterization of wild bee communities in apple and blueberry orchards

1. Wild bees provide invaluable ecosystem services in agricultural landscapes such as pollination. However, in recent decades, pollinator biodiversity, especially in wild bees, is declining on a global scale, with potentially far‐reaching consequences for crop production. Thus, there is an urgent need to determine whether wild bees are present in agricultural systems, such as fruit orchards.
2. In the present study, we examined the wild bee fauna at species and community levels during the period of bee activity (May to August) in apple and high‐bush blueberry orchards in New England.
3. Bee communities are crop‐specific and dominated by very few species, which fluctuate according to crop and season. The blueberry associated bee fauna was more diverse. In apple, communities were phylogenetically clustered at the genus level and dominated by solitary ground nesting bees within the genus Andrena. Species fluctuated widely in presence and abundance throughout the season, leading to differences in community composition and functional trait structure.
4. The results obtained in the present study show that apple and blueberry harbour a distinct and diverse bee fauna that performs vital pollination services in orchards. Our results provide essential baseline data for wild bees in blueberry and apple orchards and this can be used to improve management and conservation strategies for wild bee preservation in these crops.

     

Habitat loss and degradation due to farming intensification modify the floral visitor assemblages of a semiarid keystone shrub

1. The expansion of intensive agriculture has severely altered landscapes, a process that has been aggravated by the increase of greenhouse agriculture. However, few studies have considered the combined effects of habitat loss/degradation and greenhouse farming on insect visitors to native plants.
2. We analysed how habitat loss/degradation and greenhouse farming are related to the composition, abundance, and richness of the insect assemblages visiting flowers in a semiarid keystone shrub (Ziziphus lotus) in southeast Spain, home to Europe's largest area of greenhouses. We studied 21 populations distributed across a gradient of greenhouse intensification and habitat loss.
3. The composition, abundance, and richness of the Ziziphus insect assemblage substantially varied between populations and were differently affected by natural habitat-remnant and landscape degradation and population isolation.
4. Insect abundance was negatively affected by habitat loss at population level but positively affected at individual Ziziphus scale. Honey-bee relative abundance increased in highly degraded landscapes and isolated populations, being positively associated with hoverflies and negatively with ants and bee-flies. Wild bees, carrion flies, and wasps remain neutral along the degradation axes. Insect visitor abundance per plant affected positively the flower visitation rate, which was also favoured by the relative abundance of honey bees, wild bees, and hoverflies. Species richness was not influenced by anthropogenic degradation, and did not affect flower visitation rate.
5. Our results highlight the fragility of wild pollinator communities to landscape and habitat degradation, and the need to regulate intensive farming practices to preserve wild insect pollinator assemblages in semiarid habitats.

     

Orchard pollination in Capitol Reef National Park,Utah, USA. Honey bees or native bees?

Capitol Reef National Park in central Utah, USA surrounds 22 managed fruit orchards started over a century ago by Mormon pioneers. Honey bees are imported for pollination, although the area in which the Park is embedded has over 700 species of native bees, many of which are potential orchard pollinators. We studied the visitation of native bees to apple, pear, apricot, and sweet cherry over 2 years. Thirty species of bees visited the flowers but, except for pear flowers, most were uncommon compared to honey bees. Evidence that honey bees prevented native bees from foraging on orchard crop flowers was equivocal: generally, honey bee and native bee visitation rates to the flowers were not negatively correlated, nor were native bee visitation rates positively correlated with distance of orchards from honey bee hives. Conversely, competition was tentatively suggested by much larger numbers of honey bees than natives on the flowers of apples, apricots and cherry; and by the large increase of native bees on pears, where honey bee numbers were low. At least one-third of the native bee species visiting the flowers are potential pollinators, including cavity-nesting species such as Osmia lignaria propinqua, currently managed for small orchard pollination in the US, plus several fossorial species, including one rosaceous flower specialist (Andrena milwaukiensis). We suggest that gradual withdrawal of honey bees from the Park would help conserve native bee populations without decreasing orchard crop productivity, and would serve as a demonstration of the commercial value of native pollinators.     

The relationship between the abundances of bumblebees and honeybees in a native habitat

Abstract. 1. The western honeybee, Apis mellifera, has been introduced to many parts of the world and is sometimes purported to be detrimental to native bees because it reduces their food base. It is seldom viewed in this light in Europe; however, when beekeepers maintain very high bee densities, the species could also be displacing insects in its native European range by reducing the resource base. 2. In England, populations of bumblebees (Bombus Latr. Hym.) have been decreasing both in terms of diversity and abundance, mainly because of a loss of habitat resulting from agricultural intensification. The impact of competition from other flower feeders is largely unknown. 3. Nineteen dry lowland heaths in southern England were sampled once for honeybees and bumblebees. Honeybee abundance varied from 4 to 81 bees per 100 m² (mean = 30.89, median = 23), whereas bumblebees varied from 2 to 17 individuals per 100 m² (mean = 8.26, median = 7), belonging to between one and five species. There was a negative association between honeybee and bumblebee abundance but there was no apparent relationship between honeybee abundance and bumblebee diversity. 4. The Bray–Curtis coefficient was used to compare the similarity in honeybee and bumblebee floral host breadth at these 19 sites. The coefficient was negatively associated with honeybee abundance: thus where honeybees were most abundant, bumblebees were fewer and/or foraged on different flower species. 5. Foraging host breadth was also examined at four heathlands over a field season (April to September). No association between honeybee abundance and foraging host breadth was found for short‐tongued bees, although there was some evidence for a change in floral host breadth for long‐tongued bees. 6. It is concluded that the impact of honeybees on bumblebees is complex. Although competition between the two species cannot be ruled out, it is perhaps equally likely that bumblebees decline in response to other factors, and that honeybees move independently of this decline.     

Native flowering shrubs promote beneficial insects in avocado orchards

1. Flower strips can promote and conserve beneficial insects in agroecosystems. Knowing which groups are favoured and which plant traits affect visitation rates by beneficial insects is important for the design of plant strips.
2. We established 21 Native Flower Strips (NFS) in avocado orchards in Central Chile. NFS contained 7–11 plant species, with variable corolla length and flowering period, to promote beneficial insects. We assessed flight activity of ladybirds (Coccinellidae) and bees (Apiformes) in sites adjacent to and far from NFS within avocado orchards. Additionally, we evaluated flower visitation for the main flower visitor groups (Apiformes, Lepidoptera, Diptera, and Coleoptera) to the plant species in NFS according to season and corolla length.
3. We found almost six times greater flight activity of coccinellids and bees in NFS than sites far from NFS within avocado orchards. Visitation rates of pollinator groups varied according to corolla length and season. Diptera, Coleoptera, and Lepidoptera consistently visited short corolla flowers. NFS were highly visited in summer and autumn, when avocados were not in bloom.
4. NFS in orchards should be encouraged by policymakers because they support beneficial insects that could deliver ecosystem services and contribute to local biological conservation.

     

Using the waggle dance to determine the spatial ecology of honey bees during commercial crop pollination

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Key factors influencing forager distribution across macadamia orchards differ among species of managed bees

To achieve maximised and sustainable crop productivity, it is critical that we develop crop-specific strategies for managing pollination. Honey bees (Apis mellifera) and stingless bees (Tetragonula carbonaria) are considered effective pollinators of macadamia (Macadamia integrifolia). The introduction of managed honey bee or stingless bee hives into orchards is likely to boost the numbers of these insects visiting flowers; however, there is a lack of published information and consensus regarding their management for pollination. Here, we identify factors that affect the distribution of both honey bees and stingless bees across cultivated macadamia, and establish whether increased flower visitation leads to higher nut set. A gradient of bee visitation rates was created by placing colonies on the ends of a four-hectare block, and mixed-effect models were applied to assess forager abundance and nut set with respect to distance from hive, time of day, cultivar, and floral display size. Distance from colony had a strong effect on stingless bee numbers, with >96% of individuals recorded within 100 metres of colonies, whereas the distribution of honey bees was more closely related to daily floral display: trees with greater numbers of flowers attracted more honey bees. Simplified surveys conducted in a further 17 macadamia blocks confirm that these are broadly occurring distribution patterns. Bee abundance alone did not significantly predict nut production; however, an indirect effect of bee visits to flowers is inferred, as nut production increased with size of floral display. To encourage a more even distribution of bees and uniform pollination, we recommend placement of stingless bee hives to maximise their distribution through a block (e.g. at 100-m intervals) and management practices that promote even distributions of flowers across trees.     

Effects of landscape cover and local habitat characteristics on visiting bees in tropical orchards

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Effects of landscape structure and climate seasonality on pollen intake by honeybees in Neotropical highland agroecosystems

1. Pollen is the main protein source for honeybee brood and so colony development relies heavily on the availability of pollen in the environment. Intensification of agriculture and climate seasonality are known to alter honeybee pollen intake in temperate regions through changes in resource availability; however, little is known about how honeybees respond to such environmental factors in tropical regions.
2. Pollen collected by honeybees was sampled from apiaries in a Neotropical highland region of Colombia. Pollen species were identified and the effects of landscape diversity, forest area and mean monthly precipitation on the pollen intake by honeybees were evaluated for all pollen species together and pollen species segregated according to forest and anthropic areas.
3. Honeybees were found to be much more associated with anthropic than forest pollen species regardless of landscape structure or precipitation. However, pollen intake from all species and forest species responded positively to landscape diversity and forest area. Precipitation was found not to be related to the overall amount and overall richness of pollen collected by honeybees. Nonetheless, overall pollen diversity was negatively affected by precipitation in less diverse landscapes, whereas anthropic pollen diversity was negatively affected by precipitation in more forested landscapes.

     

The relative importance of birds and bees in the pollination of Metrosideros excelsa (Myrtaceae)

Exclusion experiments were used to assess the effect of different pollinator groups on outcrossing and seed production in Metrosideros excelsa. The main study site was Little Barrier Island, New Zealand where indigenous bird and native solitary bees are the main flower visitors. Our results showed that native birds were more important pollinators of M. excelsa than native bees. Seed production was much higher in open pollination than in two exclusion experiments where either birds were excluded and native bees only had access to flowers, or where all pollinators had been excluded. The number of fertile seeds per capsule was 45% higher after open pollination than in treatments with bee visitation only and 28% higher than in treatments where all flower visitors were excluded. Estimated outcrossing rates were significantly higher (t_m = 0.71) for open pollination in the upper canopy (>4 m above‐ground level) where bird visitation is presumed to be more frequent than for a treatment with native bee access only (t_m = 0.40). Our results also suggest that a large proportion of seeds (66%) arise from autonomous self‐pollination when all pollinators are excluded. In four trees of a modified mainland population with predominantly introduced birds and a mixture of introduced and native bees there was no decrease in seed production for the treatment allowing bee access only, indicating that – in contrast to native bees – honeybees may be more efficient pollinators of M. excelsa. Observation of the foraging behaviour of both groups of bees showed that native bees contact the stigma of flowers less frequently than honeybees. This is likely to be a consequence of their smaller body size relative to honeybees.     

Native bees with floral sonication behaviour can achieve high-performance pollination of highbush blueberry in Chile

1. Blueberry is one of the most relevant buzz-pollinated crops worldwide and Chile is the most important global producer of fresh blueberries during wintertime in the Northern Hemisphere. Thousands of exotic Bombus terrestris are imported from Europe to pollinate blueberries. However, no study has investigated the performance of the native Chilean fauna to pollinate blueberry or other crops. Therefore, we aimed to compare the performance of native Chilean floral visitors with managed visitors to pollinate highbush blueberry.
2. Per-visit pollination performance (stigmatic pollen deposition) and floral visitation were measured and the presence of sonication behaviour of flower visitors was evaluated for five cultivars in two blueberry orchards located in southern Chile.
3. Floral visitors showed a preference for one or more blueberry cultivars, instead of visiting all cultivars equally. Floral visits with sonication deposited more conspecific pollen on stigmas than visits without sonication. Some native sonicating bees (Cadeguala and Bombus), especially Cadeguala occidentalis, were efficient pollen vectors of blueberry and better pollinators than honeybees (5.8 times more pollen transferred) similar to that of the managed bee B. terrestris.
4. The results indicate that some Chilean native bee species, especially those with sonication behaviour, can provide pollination service to highbush blueberry crops.

     

Native pollinators increase fruit set while honeybees decrease the quality of mandarins in family farms

Family farms can benefit from the presence of a diverse set of native pollinators and associated pollination services. In the present study we assessed the effect of flower visitor richness and visitation rate by honeybees and native insects on mandarin production (Citrus reticulata `Criolla´), in ten citrus family farms located in the Dry Chaco region of northwest Argentina. An exclusion experiment was conducted to explore how pollinators influence the fruit set and quality of `Criolla´ mandarin. The influence of features such as local richness and abundance of flowering plants, farm size, and surrounding natural/semi-natural habitats in the diversity of flower visitors was also evaluated. Fruit set in open pollination branches was three times higher than in bagged branches, where flower visitors were excluded. Moreover, the mandarin fruit set increased with a higher native visitation rate, and mandarin quality (fruit weight and size) decreased with a higher honeybee visitation rate. Flower visitor diversity was higher in farmlands with a greater proportion of surrounding natural and semi-natural habitats. Our results demonstrate the negative effects of excessive honeybee visitation on citrus fruit quality and highlight the importance of native pollinators and natural habitat conservation to increase the fruit set and quality of mandarin in family farms.     

Crematogaster chiarinii ants as a potential biological control agent for protecting honeybee colonies from attack by Dorylus quadratus driver ants in Ethiopia (Hymenoptera: Formicidae)

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Improved monitoring of female codling moth (Lepidoptera: Tortricidae) with pear ester plus acetic acid in sex pheromone-treated orchards

The performance of clear delta traps baited with 3.0 mg of pear ester, ethyl (E,Z)-2,4-decadienoate, and 5.0 ml of acetic acid in separate lures was compared with orange delta traps baited with a single lure containing 3.0 mg of both pear ester and the sex pheromone, (E,E)-8,10-dodecadien-1-ol (codlemone) for codling moth, Cydia pomonella (L.), in apple, Malus domestica (Borkhausen). Residual analyses and field tests demonstrated that both the pear ester and acetic acid lures were effective for at least 8 wk. The two trap-lure combinations caught a similar number of total moths in an orchard treated with sex pheromone dispensers during short-term trials in 2008. However, the mean catch of female moths was significantly higher and male moths significantly lower in clear traps baited with pear ester and acetic acid versus orange traps baited with pear ester and codlemone. Season-long studies were conducted with these two trap-lure combinations in orchards treated with (n = 6) and without (n = 7) sex pheromone dispensers during 2009. The two trap-lure combinations caught similar numbers of moths in dispenser-treated orchards. In contrast, total catch was significantly higher (>2-fold) in the orange compared with the clear traps in untreated orchards. The clear caught >6-fold more females than the orange trap in both types of orchards. These studies suggest that deploying clear delta traps baited with pear ester and acetic acid can be an effective monitoring tool for female codling moth and an alternative to codlemone-baited traps in sex pheromone-treated orchards.