Bee visitation and fruit quality in berries under protected cropping vary along the length of polytunnels

Abstract

15Wild and managed bees provide effective crop pollination services worldwide. Protected 16 cropping conditions are thought to alter the ambient environmental conditions in which 17 pollinators forage for flowers, yet few studies have compared conditions at the edges and 18 centre of growing tunnels. We measured environmental variables (temperature, relative 19 humidity, wind speed, white light and UV light) and surveyed the activity of managed 20 honeybees Apis mellifera, wild stingless bees Tetragonula carbonaria and sweat bees 21Homalictus urbanus along the length of 32 multiple open-ended polyethylene growing 22 tunnels. These were spaced across 12 blocks at two commercial berry farms, in Coffs 23Harbour, New South Wales and Walkamin, North Queensland, Australia. Berry yield, fresh 24 weight and other quality metrics were recorded at discrete increments along the length of the 25 tunnels. We found a higher abundance and greater number of flower visits by stingless bees 26 and honeybees at the end of tunnels, and less frequent visits to flowers toward the middle of 27 tunnels. The centre of tunnels experienced higher temperatures and reduced wind speed. In 28 raspberry, fruit shape was improved with greater pollinator abundance and was susceptible to 29 higher temperatures. In blueberry, per plant yield and mean berry weight were positively 30 associated with pollinator abundance and were lower at the centre of tunnels than at the edge. 31Fruit quality (crumbliness) in raspberries was improved with a greater number of visits by 32 sweat bees, who were not as susceptible to climatic conditions within tunnels. Understanding 33 bee foraging behaviour and changes to yield under protected cropping conditions is critical to 34 inform the appropriate design of polytunnels and aid pollinator management within them. 35 36

Towards precision apiculture: Traditional and technological insect monitoring methods in strawberry and raspberry crop polytunnels tell different pollination stories

“…We aimed to determine if honeybee and other insect numbers differed between the edge and middle of the polytunnels as observed in previous studies [ 30 ] ( Fig 5 ). We compared insect counts at the edges of the polytunnels (Strawberries: 1–12 meters from the edge; Raspberries: 1–5 meters from the edge) with the middle of the polytunnels (Strawberries: 35–52 meters from the edge; Raspberries: 22–26 meters).…”

“…Polytunnels aid in the manipulation of the microenvironment, usually for the benefit of crop plants. Research by Hall et al (2019) [30] found that the centres of polytunnels experience higher temperatures and reduced wind speed, but also lower abundances and fewer visits from stingless bees and honeybees, than the edges [30]. Thus, it appears that polytunnels may impact pollinator access, diversity, abundance, distribution, and plant reproduction/crop yield, raising questions about how to monitor and improve this increasingly common and important horticultural infrastructure.…”

Delivering Integrated Pest and Pollinator Management (IPPM)

“…Bee colonies may alternatively be placed directly into such enclosures for pollination. However, potential risks to their use as such, and in structures such as glasshouses and tunnels, include reduced pollination efficiency and quality of yield [71,72], as well as increased vectoring of plant diseases such as viruses [73,74]. Further conflicts may need to be managed between the ability of UV-absorbing screening to suppress pest activity, for instance in whitefly and thrips [75], versus its negative effect on the foraging activity of bees [76] and parasitoids [77].…”

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.…”