What’s the Buzz? Assessing Efficacy, Synergisms, and Sustainability of Pollinators in Southern Highbush Blueberry (Vaccinium  corymbosum  L.) 

View the project final report

Commodities

• Fruits: berries (blueberries)
• Animals: bees

Practices

• Crop Production: pollination, pollinator habitat

Southern highbush blueberry (Vaccinium corymbosum L.) is highly dependent upon insect pollination with fruit set and berry weight both decreasing dramatically in the absence of pollinators. Due to this, the abundance and efficacy of pollinators is closely tied to successful blueberry production. In Florida, previous research has shown that wild pollinator visitation rates are low. This leaves growers reliant on managed honey bees (Apis mellifera L.), and still often receiving unsatisfactory pollination due in part to honey bees limited efficacy as blueberry pollinators. Bumble bees (Bombus impatiens), which are capable of buzz pollinating and can be stocked as managed pollinators, have been shown to be more effective pollinators; we found that increasing bumble bee stocking density improves fruit set and yield despite low overall visitation rates as compared to honey bees, indicating a disproportionately positive impact on blueberry pollination. However, the use of these two managed pollinators together to achieve optimal pollination has not been well studied despite the growing proportion of farmers who invest in both pollinators during bloom. The objective of this study is to test the hypothesis that managed bumble bee deployment facilitates and improves the efficacy of non-buzz pollinators by increasing rates of pollen release. Additionally, southern highbush blueberry breeding selections will be assessed to determine their attractiveness to buzz pollinators including their pollen quantity and release rates. The proposed research will provide a better understanding of whether utilizing both managed bumble bees and honey bees together is an economically sustainable approach to improving blueberry pollination.

Objective 1: Assess synergy between buzz pollinators and honey bees. The first objective will focus on the pollen deposition of honey bees both in the presence and absence of buzz pollinators. This will provide insight into the mechanisms by which honey bees are able to encounter and deposit blueberry pollen. We know that honey bees are depositing small amounts of pollen when visiting blueberry flowers, even during nectar foraging (Rogers et al. 2013, Benjamin and Winfree 2014). However, it is not clear how they are coming into contact with pollen and what role previous visitors, including buzz pollinators, are playing. Are honey bees able to release pollen on their own despite their inability to buzz pollinate or are they encountering pollen as a result of previous buzz pollination? If the latter mechanism is correct, then the presence of buzz pollinators would likely have a synergistic impact on pollination by increasing pollen release and facilitating honey bee pollination efficacy.

Objective 2: Evaluate pollen quantity and release rates across blueberry genotypes. The second objective will assess how breeding selections vary in pollen quantity and release when buzz pollinated. This will provide a framework for assessing what breeding selections could receive optimal pollination services from both buzz and non-buzz pollinators. We predict that cultivars will vary in their total available pollen quantity as well as the release rate of pollen that occurs in response to buzz pollination. These two factors in combination would influence the amount of pollen that visitors would encounter, thereby influencing both pollinator recruitment and pollen transfer. In collaboration with the Blueberry Breeding Program at UF, we will be able to highlight certain selections to inform future breeding efforts. This outcome would provide producers with cultivars that exhibit greater pollination success.

Objective 3: Examine the influence of floral traits on pollinator visitation and behavior. Finally, the third objective will examine the influence of these pollen traits including pollen quantity and release rates on pollinator recruitment and pollination efficacy. If these traits are in fact impacting pollinator recruitment and behavior, they could play a key role in pollen transfer and pollination success.. These understudied traits could play an important role in the attraction and effectiveness of pollinators and represent an area of interest for plant breeding to improve pollination. Examining variation across selections in pollen quantity and release will enhance our understanding of why growers report differences in fruit set and yield across cultivars as well as improve our understanding of the efficacy of pollinators.