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How to Manage the Blue Orchard Bee As An Orchard Pollinator
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... With this question in mind, we observed the development of a native bee species, Osmia lignaria (Figure 1), across an elevational gradient in the Rocky Mountains, USA. Known commonly as the blue orchard bee, O. lignaria is a univoltine (single generation per year) solitary (non-social) bee that nests within hollow stems and reeds (Bosch & Kemp, 2001). On 10 May 2023, fully provisioned reeds (representing a cohort of wild O. lignaria eggs) were collected in the foothills of the Rocky Mountains in Salt Lake City, UT, at an elevation of approximately 1320 m. ...
... It needs to be emphasized how extraordinary it is that the higher-elevation larvae would consistently leave food unfinished. O. lignaria larvae, as well as most solitary bee larvae, receive a single dietary provision, all of which is typically consumed by the developing larva (Bosch & Kemp, 2001), as demonstrated by the larvae at the lowest elevation in our study (Figure 1e). The fact that the surviving bees at the higher elevations left food unfinished suggests there was some aspect of altitude that had altered their behavior/phenotype. ...
... Exemplifying this dynamic is a study of temperature in solitary bees (the red mason bee, Osmia bicornis), which found that relatively hot temperatures resulted in smaller adult bees (Kierat et al., 2017). The bee larvae in our study experienced temperatures that were broadly similar to each other (means: 20-22 C; ranging from 18 to 30 C), and all were within the normative temperature range for this bee species (Bosch & Kemp, 2001). If the bees had been subjected to the cooler temperatures typical of higher altitudes, the temperature-size rule would predict larger adult sizes (Atkinson, 1994), yet we found the opposite. ...
... One hypothesized mechanism for the impacts on performance of O. bicornis overwintering at warmer temperatures is increased energy consumption. Higher metabolic rates and consequently a depletion of the fat reserves stored in the fat bodies of bees overwintering at warmer temperatures are predicted to result in less vigorous bees and reduced longevity 21 or offspring provisioning performance, and ultimately reproductive success [16,19,49]. In fact, some studies have observed increased fat body depletion in solitary bees, including Osmia bees, exposed to longer wintering periods and warmer overwintering temperatures, and especially for bees exposed to longer pre-wintering periods [16][17][18][19][20]49,50 . ...
... Higher metabolic rates and consequently a depletion of the fat reserves stored in the fat bodies of bees overwintering at warmer temperatures are predicted to result in less vigorous bees and reduced longevity 21 or offspring provisioning performance, and ultimately reproductive success [16,19,49]. In fact, some studies have observed increased fat body depletion in solitary bees, including Osmia bees, exposed to longer wintering periods and warmer overwintering temperatures, and especially for bees exposed to longer pre-wintering periods [16][17][18][19][20]49,50 . Such increased fat body depletion due to longer pre-wintering durations has also been proposed to account for reduced longevity of hatched Osmia bees 36,50 . ...
Solitary wild bees play a key role as pollinators of wild plants and crops, but they are increasingly at risk from anthropogenic global change, such as climate warming. However, how warmer temperature during overwintering affects reproductive success of those bees remains largely unknown. In a semi-field experiment we assessed individual life-long reproductive success of 144 females of the solitary bee species Osmia bicornis that had been wintered at three different temperatures. Overwintering mortality of bees was on average 32% higher at winter temperatures of 8 °C compared to 4.5 °C–0 °C, at which almost all bees successfully emerged. After wintering at 4.5 °C and 8 °C females produced less offspring than after overwintering at 0 °C (26% or 36% less offspring, respectively). Although longevity and daily offspring production rate were not significantly affected, nesting duration of females wintered at 0 °C tended to be longer (+ 2.5 days) than that of bees wintered at 4.5 °C, which likely contributed to the higher offspring production at colder overwintering temperatures. Mortality and sex ratio of offspring was not significantly affected. While future studies should also consider climatic variation during winter, these findings indicate that increasing mean overwintering temperatures could threaten O. bicornis and potentially other solitary bee populations.
... Each box housed one-hundred 7 mm × 152 mm cardboard nest tubes lined with waxed paper straws and was hung from a tree branch (ca. 1.2 m above ground) with a southeast-facing entrance, in accordance with established management practices (Bosch and Kemp 2001). Before the boxes were placed in the orchards, all the tubes within them were treated with a spray-on application of a patented chemical bee attractant (decanoic acid plus a solvent) to promote bee nesting. ...
... This dichotomy may impact pollination when relying on A. mellifera alone to provide such an important service. When cool and wet spring conditions favor orchard bloom but inhibit A. mellifera flight, O. lignaria may be able to still fly and forage (Bosch and Kemp 2001) and, therefore, provide more critical service hours for these pollinator-dependent crops. ...
Apis mellifera Linnaeus (Hymenoptera: Apis), honey bees, are the most widely used managed crop pollinators. However, their high rental cost and uncertain availability for North American orchard crops have motivated growers to explore alternative pollination options. We examined whether adding solitary, spring-flying Osmia lignaria Say (Hymenoptera: Megachilidae), blue orchard bees, as co-pollinators with A. mellifera in Washington sweet cherry and pear orchards enhances fruit set and yield compared to the use of A. mellifera alone. We added managed O. lignaria to orchard sites where A. mellifera hives were already present. Fruit set, fruit yield, and O. lignaria reproduction at O. lignaria-supplemented sites were compared to nearby, paired sites pollinated only by A. mellifera (3 paired cherry and 3 paired pear sites). For both crops, the addition of O. lignaria significantly increased fruit set but did not yield at harvest. Microscopic inspection of pollen grains from O. lignaria nest cell provisions confirmed that O. lignaria primarily visited orchard flowers. Mean retention of O. lignaria in cherry orchards was slightly higher (65%) than O. lignaria retention reported in other orchard crops (30%–60%). However, retention in pear orchards was much lower (≤20%). These results show that supplementing hives with O. lignaria in Washington spring orchard crops can increase overall pollination, but that trees fail to bear developing fruit to maturity. The strategy of using co-pollinators, O. lignaria and A. mellifera, in US orchards may act as “pollination insurance” when A. mellifera hives are in low supply or when the weather is not amenable for A. mellifera flight during the bloom period.
... Osmia lignaria Say (Hymenoptera: Megachilidae), commonly referred to as the blue orchard bee, is a native solitary bee species in North America that plays an important role in orchard pollination [11]. Understanding the biology of O. lignaria is essential for the development of management strategies to support their populations for pollination efforts [12][13][14][15]. One aspect of O. lignaria biology that has received limited attention is the production and properties of their silk cocoons. ...
Silk, a remarkable protein-based fiber spun by various arthropod lineages, has been prized for millennia, with the cocoon silk of domesticated silkworms and spiders being the most utilized and extensively studied. There is limited information on how silk can be used to investigate biology, development, and health in other silk-producing species, particularly for solitary bees such as Osmia lignaria Say (Hymenoptera: Megachilidae). Osmia lignaria, an increasingly managed solitary pollinator, produces silk cocoons during the fifth instar larval stage. We have developed a minimally invasive protocol to isolate and mechanically test O. lignaria silk fibers using a 3-D printed well plate system for rearing and two specific isolation techniques. Our protocol allows for collecting individual fibers directly from silk-spinning larvae between silk initiation and cocoon formation without preventing subsequent cocoon development, enabling silk characterization as part of larger rearing and developmental studies. For this study, isolated fibers were mounted on C-cards, facilitating diameter measurement using a microscope and mechanical testing with an MTS Synergie 100 tensile testing instrument. We successfully isolated and tested the mechanical properties of naturally spun silk from O. lignaria, with 20 fibers isolated and mechanically tested from seven larvae. Further examination of isolated silk can reveal physical, molecular, chemical, and morphological characteristics, advancing our understanding of bee silk properties and their role in bee biology, evolution, and nutritional status. This protocol provides a practical tool for researchers to isolate and study silk from silk-producing bee species.
... Species of the Osmia genus are generalists, pollinating over 150 plant species [21,22], thus positively influencing the quantity and quality of crops. This is why they have been successfully used for many years to pollinate various crops, such as orchards [23][24][25][26][27][28][29][30][31], rapeseed [32], blackcurrant [23], and strawberries [33]. Recent reports show that mason bees are also used to pollinate forest orchards of European seed trees-Tilia cordata Mill. ...
Osmia bicornis L. is a widespread and valued pollinator species. It is considered to be easy to breed, provided that the nesting material in which the bees build their nests is of sufficient quality and quantity. The aim of this study was to test several different types of nesting materials: reeds and commercial structures, including wood, MDF (Medium Density Fibreboard), plastic, paper or polystyrene. The highest levels of nest cavity occupancy were found in reeds (90%) and grooved MDF (over 80%). We have shown that maintaining mason bee colonies in polystyrene leads to reproductive losses (occupancy only 2% of nesting holes). Mason bees built the most cells in MDF (8.02 cells/hole) and wood (7.34 cells/hole), slightly fewer in plastic (6.83 cells/hole) and reeds (6.74 cells/hole), and the fewest in paper (3.67 cells/hole). The most cocoons per nest were obtained from reed (average 5.47), MDF (4.84) and plastic (4.74). We observed the highest mortality in plastic (2 larvae/hole), and the lowest in reeds (0.92 larvae/hole). In nests made of wood, MDF and paper, large nesting losses were caused by the migration of Ch. osmiae mites along and through the nest holes. The most hygienic nesting material turned out to be reed and plastic forms.
This extensive overview investigates the essential role of wild bees, including solitary bees and bumblebees, in the maintenance of biodiversity and sustaining ecosystems. Focusing on European wild bees, this chapter highlights their diverse adaptations and behaviours, emphasizing their impact on biodiversity, ecosystem support and agricultural productivity. Emphasis is placed on the intricate relationship between wild bees and flowers, particularly their vital role in pollination, which is crucial for approximately 75% of plant species. This chapter stresses the importance of acknowledging these challenges in the implementation of effective conservation measures for wild bees, including habitat preservation, reduced pesticide use and sustainable agricultural practices. In its focus on the economic valuation of pollination services, it introduces the concept of pollination value. This chapter summarizes the multifaceted exploration of wild bees, spanning their ecological, biological, economic and conservation aspects, portraying their intricate dance as essential for ecosystem health, global biodiversity and food security.
This review explores the diversity, distribution, and population dynamics of entomofauna in the agroecosystems of Thoothukudi District, Tamil Nadu. The region's unique climatic conditions and varied ecosystems, including agricultural lands, scrub jungles, and semi-arid zones, support a rich insect biodiversity. Key insect groups such as pollinators, predators, and pests play vital roles in maintaining ecological balance and agricultural productivity. Understanding their interactions and population trends is essential for developing sustainable pest management and conservation strategies.
Increased temperature variability and extreme weather events associated with climate change can be detrimental to bees and lead to their population declines. While there is some research on the effects of heatwaves on insect biology and reproduction, impacts on male insect reproduction are not well described. Solitary bees may be more exposed to temperature variation than social bees, since there is no mitigation by group thermoregulation. Here, we evaluated the effects of sublethal heat exposure (at 30 °C and 38 °C) on reproductive fitness of adult males of a solitary bee species, Osmia cornifrons . After 4 h of heat exposure, bees were maintained at 24 °C for 48 h in laboratory cages to reach sexual maturity and later analyzed for sperm abundance (quantity) and proportion of viable sperm (quality). Bees that were reared and maintained at 24 °C served as controls. Despite rehabilitation after heat exposure, both sperm quantity and quality of male O. cornifrons bees were significantly reduced in heat-treated groups compared to controls. These results demonstrate that the exposure to elevated non-lethal temperatures, even for short periods and allowing time for recovery, may negatively affect the reproductive capacity of male solitary bees. Our findings reveal a possible mechanistic explanation for wild bee population declines. Given the importance of solitary bee species (such as O. cornifrons ) in natural and agricultural landscapes, our study provides valuable insights into the potential consequences of climate change on these insect populations and the ecosystems they inhabit.
Host-associated microbes are increasingly recognized as important drivers of bee health. Surveys of bee microbiomes have primarily sampled social bees, yet non-social bees constitute the majority of species. We employed 16S and ITS amplicon sequencing to describe the diversity and composition of bacterial and fungal communities across multiple developmental stages of Osmia lignaria, an important native and managed solitary mason bee. Bacterial and fungal diversity were not significantly different across bee development. However, the composition of bacteria and fungi significantly changed between larval and fully pigmented adult stages, in agreement with dramatic changes in host morphology during metamorphosis. Many of the microbial taxa found in provisions were also present in larvae, indicating that immature bees likely acquire their microbiome from food. Notably, the most prevalent bacterial genus was Arsenophonus, a symbiont with many recorded phenotypes, ranging from reproductive parasitism to beneficial endosymbiont. Arsenophonus was found in samples from provisions and eggs, yet reached higher read counts in larvae and fully pigmented adults. The Arsenophonus amplicon sequencing variants (ASVs) detected in this study had high sequence similarity with a symbiont that displays the son-killing phenotype, suggesting that the ASVs in O. lignaria are also reproductive parasites. The causative agent of chalkbrood disease in bees, Ascosphaera, was also detected in provisions and larvae. Most other taxa present were plant pathogens or commonly found in soil. This study highlights that O. lignaria may harbor horizontally and vertically transmitted microbial taxa with diverse consequences for bee fitness.
We combined methods of geometric morphometrics and phylogenetically controlled comparisons to examine the relationship between the shape of mandibles and material used to construct the nest for 5 Osmia Panzer species. We measured leaf- and mud-using species from 2 subgenera: in the subgenus Osmia, O. lignaria Cresson (mud-user), O. cornuta Latreille (mud-user) and O. ribifloris Cockerell (leaf-user), and in the subgenus Centrosmia, O. tanneri Sandhouse (mud-user), and O. bucephela Cresson (leaf-user). Landmark-based geometric morphometrics and multivariate statistics provided a way to compare mandible shapes, distill major shape differences and visualize mandible regions that differed most among bee species. Mandible shape differed significantly among all species based on paired comparisons of Mahalanobis distances. Principal component analysis of the shape variables (relative warps analysis) revealed greater similarity between the 2 leaf-using bees, than among the mud-users. There were however, no consistent differences between these mud- and leaf-using species. Testing with two-way multivariate analysis of variance showed that the differences in shape between the leaf- and mud-using species depended on the subgenus. A broad proximate bite surface characterized leaf-using species. No such trait was common to mud-using species. Mandibles of leaf-using species may vary less because of selection on shape, or because of functional constraints for shearing and macerating leaf material: both constraints are absent in mud-using species. Mandibles of mud-using bees may respond more to selection imposed by other aspects of bee biology.