The pollination ecology of cultivated raspberry (Rubus idaeus) in the UK: comparing pollinator supply and demand at field scale

Ryan, Imogen (2023) The pollination ecology of cultivated raspberry (Rubus idaeus) in the UK: comparing pollinator supply and demand at field scale. Doctoral thesis, University of East Anglia.

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Pollinators play a crucial role in the production of food crops worldwide. Managed honey bees are often used to ensure the productivity of crops that are highly dependent on pollination, however they have been found to have negative impacts on wild pollinator communities due to competition for floral resources and the transmission of pests and pathogens. To reduce these potential impacts, the use of managed pollinators should be informed by crop-specific estimates of the pollination requirements to yield along with site-specific monitoring of pollination service provision.Implementing managed pollinators according to their requirements will prevent overstocking and reduce the associated risks of high densities of managed pollinators to wild pollinator communities.

This thesis provides a comprehensive overview of the pollination ecology of two commercial raspberry Rubus ideaus L. cultivars studied at a commercial soft fruit farm in south England, assessing their pollinator dependence and the relative importance of managed honey bee Apis mellifera and wild bumble bees Bombus terrestris for marketable fruit production. A three-year pollinator exclusion study found a 64% loss in marketable fruit weight when pollinators were excluded, showing that the raspberry cultivars studied have a high pollinator dependence. Single visit pollinator efficiency studies revealed that Apis mellifera and Bombus terrestris were equally effective per visit at pollinating raspberry flowers in this system and that two visits from either species were sufficient to produce marketable quality fruit. Pollinator visitation rates were measured using timed flower counts and day-long video observations. We found that visitation rates were significantly higher on the first day after flower opening and at the corners of the fields (<20m from both perpendicular edges) compared to locations that were <20m from a field edge. Crop flowers received an average of ~364 insect visits across the fields in 2020 and ~71 in 2021 over the flowers’ receptive period of 2.5 days. Average visitation rates did not differ between the short, timed flower counts and day-long video observations.

Monitoring raspberry crop pollinators using short, timed flower counts in the centre of fields could therefore provide valuable information on the minimum pollination service being provided to crop flowers by wild pollinators along with the need for managed pollinators. Where visitation rates meet or exceed the two visits required to produce marketable fruit, growers should maintain or reduce the stocking densities of managed pollinators to minimize the risks to wild pollinators, while visitation rates that fall short of the required two visits per flower indicate the need for additional managed pollinators to be introduced or wild pollinator conservation to be improved to maximise crop yields.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Jennifer Whitaker
Date Deposited: 20 Feb 2024 16:26
Last Modified: 20 Feb 2024 16:26


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