Blue Orchard Bees Boost Pollination of Sweet Cherry and Pear Crops

Jim Crocker
6th July, 2024

Blue Orchard Bees Boost Pollination of Sweet Cherry and Pear Crops

Blue Orchard Bee (Osmia lignaria)

Photographer: Steve Wells

Key Findings

  • The study took place in Washington sweet cherry and pear orchards, where adding blue orchard bees (Osmia lignaria) to honey bee-pollinated sites increased fruit set
  • Despite the increase in fruit set, the addition of blue orchard bees did not lead to higher yields at harvest
  • The study suggests that using co-pollinators like blue orchard bees can serve as "pollination insurance," especially when honey bee availability is low or weather conditions are unfavorable
In the realm of agriculture, pollination is a critical service that significantly impacts crop yields. Honey bees (Apis mellifera) are the most widely used managed pollinators, but their high rental costs and uncertain availability have prompted growers to explore alternative pollination options. A recent study conducted by the USDA ARS examined whether adding solitary, spring-flying blue orchard bees (Osmia lignaria) as co-pollinators with honey bees could enhance fruit set and yield in Washington sweet cherry and pear orchards[1]. The study involved adding managed O. lignaria to orchard sites where honey bee hives were already present. Researchers compared fruit set, fruit yield, and O. lignaria reproduction at supplemented sites to nearby, paired sites pollinated only by honey bees. The results showed that the addition of O. lignaria significantly increased fruit set in both cherry and pear orchards but did not lead to higher yields at harvest. This finding aligns with previous research indicating that diverse pollinator communities can modify the behavior of individual species and increase their pollination effectiveness. For example, a study on California almond orchards found that the presence of non-Apis bees led to changes in honey bee foraging behavior, resulting in greater pollination effectiveness and fruit set[2]. Similarly, the current study demonstrates that supplementing honey bee hives with O. lignaria can enhance overall pollination, even if it does not directly translate to increased yields. One of the key observations from the USDA ARS study was that O. lignaria primarily visited orchard flowers, as confirmed by microscopic inspection of pollen grains from their nest cell provisions. The mean retention of O. lignaria in cherry orchards was slightly higher (65%) compared to other orchard crops (30%-60%), but retention in pear orchards was much lower (≤20%). This variability in retention rates suggests that environmental factors and specific crop characteristics may influence the effectiveness of O. lignaria as co-pollinators. Interestingly, a previous study on O. lignaria co-pollination in Utah commercial tart cherry orchards found no measurable increase in fruit set or yield when these bees were paired with honey bees[3]. The lack of differences was attributed to local saturation of pollinator services supplied by managed honey bees, indicating that the benefits of O. lignaria supplementation may be context-dependent. Despite the mixed results, the USDA ARS study highlights the potential of using co-pollinators like O. lignaria as "pollination insurance." This strategy can be particularly valuable when honey bee hives are in low supply or when weather conditions are not conducive to honey bee flight during the bloom period. By ensuring that multiple pollinator species are available, growers can mitigate risks associated with pollination shortages and improve the resilience of their agricultural systems. The study also touches on the broader issue of pollinator health and diversity. Bumble bees, for example, have experienced significant declines in North America due to factors like pathogen infection and reduced genetic diversity[4]. Ensuring a diverse and healthy pollinator community is essential for maintaining robust pollination services and supporting agricultural productivity. Additionally, addressing nutritional stress on bee populations is crucial for their conservation. Efforts to provide alternative nutritional resources through agri-environmental protection schemes should focus not only on the quantity and timing of flowering plants but also on the quality of nectar resources. Social bees are particularly sensitive to nectar sugar concentrations, which directly impact their fitness[5]. By improving the quality of floral resources, we can help alleviate nutritional stress and support healthier bee populations. In conclusion, the USDA ARS study provides valuable insights into the potential benefits and limitations of using O. lignaria as co-pollinators with honey bees in orchard crops. While the addition of O. lignaria can enhance fruit set, it does not necessarily lead to increased yields. However, the strategy of using co-pollinators offers a form of pollination insurance, contributing to more resilient and sustainable agricultural practices. This research underscores the importance of maintaining diverse and healthy pollinator communities to support crop production and ecosystem services.

AgriculturePlant ScienceAnimal Science

References

Main Study

1) Osmia lignaria (Hymenoptera: Megachilidae) increase pollination of Washington sweet cherry and pear crops.

Published 4th July, 2024

https://doi.org/10.1093/ee/nvae043

Related Studies

2) Synergistic effects of non-Apis bees and honey bees for pollination services.

https://doi.org/10.1098/rspb.2012.2767

3) Assessing blue orchard bee (Osmia lignaria) propagation and pollination services in the presence of honey bees (Apis mellifera) in Utah tart cherries.

https://doi.org/10.7717/peerj.7639

4) Patterns of widespread decline in North American bumble bees.

https://doi.org/10.1073/pnas.1014743108

5) The nectar report: quantitative review of nectar sugar concentrations offered by bee visited flowers in agricultural and non-agricultural landscapes.

https://doi.org/10.7717/peerj.6329


Related Articles

An unhandled error has occurred. Reload 🗙