Bee Visitation and Fruit Quality in Berries Under Protected Cropping Vary Along the Length of Polytunnels

Abstract

Wild and managed bees provide effective crop pollination services worldwide. Protected cropping conditions are thought to alter the ambient environmental conditions in which pollinators forage for flowers, yet few studies have compared conditions at the edges and center of growing tunnels. We measured environmental variables (temperature, relative humidity, wind speed, white light, and UV light) and surveyed activity of the managed honey bee, Apis mellifera L.; wild stingless bee, Tetragonula carbonaria Smith; and wild sweat bee, Homalictus urbanus Smith, along the length of 32 multiple open-ended polyethylene growing tunnels. These were spaced across 12 blocks at two commercial berry farms, in Coffs Harbour, New South Wales and Walkamin, North Queensland, Australia. Berry yield, fresh weight, and other quality metrics were recorded at discrete increments along the length of the tunnels. We found a higher abundance and greater number of flower visits by stingless bees and honey bees at the end of tunnels, and less frequent visits to flowers toward the middle of tunnels. The center of tunnels experienced higher temperatures and reduced wind speed. In raspberry, fruit shape was improved with greater pollinator abundance and was susceptible to higher temperatures. In blueberry, per plant yield and mean berry weight were positively associated with pollinator abundance and were lower at the center of tunnels than at the edge. Fruit quality (crumbliness) in raspberries was improved with a greater number of visits by sweat bees, who were not as susceptible to climatic conditions within tunnels. Understanding bee foraging behavior and changes to yield under protected cropping conditions is critical to inform the appropriate design of polytunnels, aid pollinator management within them, and increase economic gains in commercial berry crops.

Overview of Bee Pollination and Its Economic Value for Crop Production

“…The number of visits and the aggregate effects of various bee species influence not only the quantity of crops produced but also their quality, which is important mainly from an economic perspective [37]. Plant pollination by more than one bee species, including honey bees, carpenter bees, stingless bees, bumble bees, long-tongued bee, feral bees, social bees, and solitary bees, results in a better pollination/vegetation process, as shown in Table 1.…”

Morphometric comparisons and novel observations of diurnal and low-light-foraging bees

“…not referred to as a subgenus of Lasioglossum) as has been done in most recent literature (e.g. (Bernhardt et al 2019;Dorey et al 2019;Hall et al 2020;Neave et al 2020)). Thirteen additional non-Australian bee specimen images were sourced from the Natural History Museum UK (Natural History Museum 2014a) in order to provide broader taxonomical and geographical low-light representation.…”

The Role of Flies as Pollinators of Horticultural Crops: An Australian Case Study with Worldwide Relevance

“…In addition, honey bees sometimes find carrot and onion seed crops less attractive than other nearby forage sources, and thus leave the target crop to forage elsewhere [ 89 ]. In protected crops, enclosure coverings can also compromise the ability of honey bees to navigate and forage normally [ 91 , 92 ]. Given the substantial reliance on managed honey bees to pollinate vegetable seed crops, and the challenges that this can present for achieving reliable yields in some situations, efforts to develop alternative pollinators for use in this context are warranted.…”

“…Foraging bees rely on the sun as a primary reference for navigation and communication, and thus, cloudy conditions and protective cropping systems can negatively impact on foraging activity [ 91 , 92 ]. In contrast, blow flies show potential as pollinators for the greenhouse industry, as they may be less sensitive to heat, humidity, solar radiation and UV distortion than honey bees.…”