We now know that blue-green blue-banded bees are useful pollinators of lucerne. After honey bees, these bees are also among the most abundant bees in lucerne crops. If we want to capitalize on their free pollination services, we need to stimulate their presence.
The main reason for low numbers of native bees in crops is a lack of food in the landscape, in particular when the crop is not in flower. So, to stimulate bee numbers, we need to plant bee food. And to do that effectively, we need to know when these bees are active, how far they will forage and what kind of food plants they need.
When are food plants for blue-banded bees needed?
Blue-banded bees are active between mid-late October and late April. Therefore, their presence will always coincide with lucerne flowering. Blue-banded bees live only short (5-6 weeks), but they produce multiple generations a year. So ideally, they will need flowers from mid-spring to mid-autumn.
Where do blue-banded bees need to find food?
How far blue-banded bees fly from their nest to obtain their food has not been assessed. General patterns among bees suggest that, given their size, blue-banded bees would forage at distances of about 300 – 400 m from their nests. When we don’t know where their nests are, we could supply a windbreak with food for blue-banded bees every 300 m. And if we chose our plants carefully, this will help to provide shade and shelter for sheep as well.
Food plants for blue-banded bees
Bees need pollen (protein) and nectar (carbs) to survive and reproduce. But not all bees forage on all flowers. Like honey bees, blue-banded bees are generalist foragers and benefit from a range of native, introduced and crop plants. But unlike honey bees, blue-banded bees are a buzz pollinating species. Buzz pollinated flowers require the pollen to be shaken out of the anther cone, and blue-banded bees do this by head banging the flower at 320 times per second! In gardens, they will buzz pollinate tomatoes and forage on a range of introduced plants such as catmint (Nepeta), flowering basil, lavender, Duranta and Salvia.
For planting up patches or hedgerows, suitable native buzz pollinated plants include guinea flowers (Hibbertia), Senna, native Solanums, and flax, fringe and chocolate lilies. However, buzz pollinated flowers do not produce nectar. So in addition to these plants, add species that provide nectar such as dryland tea tree/ honey myrtle (Melaleuca), Eucalyptus, Sweet Bursaria, Hakea and fanflowers (Scaevola), and, in wetter areas, bugleweed (Ajuga).
This is only a selection; there are many more plant species that can provide blue-banded bees with food. Local native nurseries and organisations such as Trees for Life in South Australia, or Greening Australia, can assist with the selection of species that are suitable for your region.
This project is supported by AgriFutures Australia, though funding from the Australian Government Department of Agriculture and Water Resources as part of its Rural R&D for Profit Program, as well as Horticulture Innovation Australia. The project is being led by the University of Adelaide with further support from Adelaide and Mount Lofty Ranges Natural Resources Management Board, Department of Environment Water and Natural Resources SA, Apple and Pear Growers Association (SA), Lucerne Australia, Native Vegetation Council, Natural Resources Northern and Yorke, O’Connor NRM, Primary Industries and Resources SA, South Australian Apiarist Association, Terrestrial Ecosystems Research Network Eco-informatics and Trees For Life.
Dr Katja Hogendoorn is a Research Associate in the School of Agriculture, Food and Wine, University of Adelaide here at the Waite campus.
This article was originally published on her Wild pollinators of lucerne blog.
Native blue-banded bee pollinating lucerne. Photo: K. Hogendoorn