Welcome back to my second blog about wild pollinators in lucerne!
In last week’s blog, we saw that wild pollinators contribute on average A$22 M to the production of dryland lucerne seed. But how important are they for irrigated lucerne seed production?
The short answer is: we don’t know, but we can make an educated guess. As a percentage, their contribution is likely to be lower than in dryland lucerne, simply because all growers of irrigated lucerne use hived bees. This is not surprising: irrigated lucerne has a much higher flower density, so more bees are needed per acre. And although wild pollinators are definitely present as well, some irrigation strategies are likely to limit their presence.
Most wild pollinators of lucerne nest in the soil. One nest can contain many females. (photo: Lea Hannah).
Wild bees make their nest either in the soil, in stems and twigs, or in hollows in wood. Many wild bee pollinators of lucerne nest in the soil. They cannot deal with flooding of their nest, so we won’t find their nests in border check irrigated paddocks. Pivot irrigation is likely to hinder the soil nesters less, but this has not been investigated.
A second reason why nesting opportunities may be lacking is that paddock trees, while common in dryland, are rare in irrigated blocks. Paddock trees provide food and a place to nest for wood nesting bees, including feral honey bees. In the coming two years, Scott Groom will investigate the importance of paddock trees for the presence of pollinators in lucerne.
Paddock trees provide pollinators with food and shelter
However, despite the irrigation and lack of paddock trees, we still find wild pollinators in irrigated lucerne. Among the most abundant species are blue-banded bees. Last week, I promised to write about these beautiful bees, which is coming up next week!