Blue-banded bees: pollinators of lucerne?

Welcome back to the fifth blog about the wild pollinators of lucerne!

In the first two blogs, we saw that wild pollinators contribute on average A$ 22 M to the production of dryland lucerne seed. The wild pollinators include the feral honey bees and native bee species.
Among the native bees, two blue-banded bee species are particularly  abundant in the lucerne growing regions around Keith: the blue-green blue-banded bee (Amegilla chlorocyanea) and Murrray’s blue-banded bee (A. murrayensis). They look alike, but with a little bit of training, the difference is clear:

Abdomen of female blue-green (left) and Murray’s blue-banded bees (Leijs et al 2017)

Do these common blue-banded bee species pollinate lucerne?

Several lines of evidence indicate that only the blue-green blue-banded bee (left above) pollinates lucerne:

  • This species has been caught on lucerne flowers – Murray’s bee hasn’t;
  • Both male and female blue-green blue-banded bees have been found to carry lucerne pollen on their body, which shows that they have recently tripped flowers;
  • Lucerne pollen can be found on the hind legs of female blue-green blue-banded bees. This indicates that they use the pollen to rear their offspring;
  • We trialed the two species in captivity for their ability to pollinate lucerne – see below.

Preliminary experiments: The blue-green versus Murray’s blue-banded bee

The blue-green blue-banded bee

In 2006, Katja was using blue-banded bees for greenhouse tomato pollination. Driven by curiosity, she did a pilot study to investigate the ability of the bees to pollinate lucerne. Katja used a single isolation cage with nine blue-green blue-banded bees, and compared the seed yield per 100 plants to a cage containing about 500 foraging honey bee workers (a tiny nucleus hive). Initial results indicated equal set in both cages and a higher seed set per bee for blue banded bees.

A small cage trial in 2006 indicated good pollination by blue-green blue-banded bees

Murray’s blue-banded bee

In 2011, with funding from AgriFutures (then RIRDC), the pollination experiment was repeated in two greenhouses. However, in this case, Katja used Murray’s blue-banded bees. Why? Convenience, really. It was the species she was working with at the time, and there was no reason to assume it would make much difference. After all, both are common species, visit other crops, and they look very similar. But the results were unexpected: In captivity, Murray’s blue-banded bees ignored the lucerne flowers, and there was no seed set. However, these results remain preliminary – academic rigour calls for replicated trials in the exact same conditions.

Thus, all evidence indicates that blue-green blue-banded bees are among the wild pollinators of lucerne, while Murray’s blue-banded bee may not be. This implies that enhancing the abundance of blue-green blue-banded bees in and around a crop will lead to more secure crop pollination services.                                                                                   But how do we achieve that?

 

Enhancing the abundance of crop pollinators through revegetation

cropped-male-lucerne-close-up.jpgThis blog is part of a larger project, “Secure Pollination for more Productive Agriculture”, funded by the department of Agriculture and Water Resources, through its Rural Industries for Profit program.

The sub-program in South Australia, is called “Secure pollination through revegetation”. Researchers from The University of Adelaide investigate how wild pollinators and managed honey bees can be supported around crops. We work in lucerne, canola, apple and almond.

See our video for more information on the project in South Australia.

 

Acknowledgeents SAFor more information visit: http://www.agrifutures.com.au/securing-pollination

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On trees, bees and the importance of managed hives in lucerne

Apologies for the blog-lag!

We have been very busy observing the bees foraging on flowering lucerne. Scott Groom has been particularly active, as he has been looking at the quality of lucerne pollination in relation to old Eucalyptus trees in the landscape.

So why look at the effects of these old trees? Well, worldwide, there is a correlation between proximity of woody vegetation, bee densities and the yield of pollination dependent crops. In Australia, feral honey bees, which nest in hollows in old Eucalyptus trees, provide a substantial share of the free pollination.

But how large are these benefits and over what distance do they play out?

To estimate that, Scott and his team have quantified the densities of bees and the set in lucerne, relative to the presence of old eucalypt trees.

Specifically, the team quantified bee visitation and set:

  • At different distances from field edges that contained large eucalypt trees, housing one or more feral honey bee hives;
  • In fields with scattered old ’paddock trees’, throughout, see for example below;
  • At different distances from field edges without eucalypts, but containing a large drop of managed honey bee hives;

Scott will need another two years of data collection to get the full picture, but he’ll share some of his very interesting preliminary findings.

scattered trees with f;owering lucerne
Scattered large paddock trees often house feral honey bee hives. Such fields have a more even set than fields without trees.

Proximity of large eucalypt trees benefit set in lucerne

The team discovered that there were twice as many honey bees foraging on lucerne in close proximity of field margins with native vegetation that included old eucalypts, than at field edges that lacked native vegetation. More importantly, they found that this higher density of bees was reflected in pod set: Going into the paddock, set was 30% higher at 75 m than at 300 m from the margin that contained native vegetation (data averaged across three replicate transects).

Scattered paddock trees also had an effect on pod set, which was more evenly distributed over the block, than in fields that had eucalypts only along the edge.

Although Scott’s results remain preliminary, there are already two important implications:

  • Firstly, if the closest old eucalypt trees are more than 250 m away from the paddock, your yield will probably benefit substantially if you order in hives from a beekeeper. This would likely be the case in most pivot and flood irrigated lucerne.
  • Secondly, planting trees for bees, maintaining paddock trees and caring for the vegetation in the field margins will ultimately support pollinator populations, and help to enhance and secure their free pollination services.
Jay Iwasaki and Lizzy Williamson
Jay Iwasaki and Lizzy (aka Spud) Williamson, who assisted with the fieldwork

Scott and I would like to thank Jay and Lizzy, for their fabulous field assistance.

After this intermezzo about Scott’s work we will continue our exploration of the wild pollinators of lucerne next week.

Acknowledgeents SAfor more information visit: http://www.agrifutures.com.au/securing-pollination

 

The blue-banded bee species around Keith

Welcome to the third blog about wild pollinators in lucerne!

In the first two blogs, we saw that wild pollinators contribute on average A$22 M to the production of dryland lucerne seed, while their share in the production of irrigated lucerne is unknown. Now that we have some inkling of their value, it is time to explore some of these wild pollinators.

Which species are they, when are they active, where do they make their nests, how do we know they pollinate lucerne, and importantly, what support do they need from the surrounding landscape? That’s a lot of questions to answer!  Today, we’ll start by finding out more about blue-banded bees.

Henbury Station Bush Blitz 2013 Photo by Jo Harding
Green-blue-banded bee (Amegilla chlorocyanea; photo: Rob Whyte)

A revision published earlier this year shows there are 14 species of ‘blue-banded’ bees in Australia, but not all have blue bands! As can be seen below, some have green, white or orange bands. In most species the hairbands are iridescent and their colour depends on the angle at which you look at them.  While identification of the individual species can be tricky, there are only two blue-banded bee species in the lucerne growing area around Keith. Unfortunately, they only have Latin names, but let’s call them the green-blue-banded bee (Amegilla chlorocyanea; 25) and Murray’s blue-banded bee (Amegilla murrayensis; 32).

abdomen chlorocyanea
Bums of female Australian blue-banded bees, which excite males of the species differentially! The green-blue-banded bee (25) and Murray’s blue-banded bee (32) are common around Keith.

So how can you tell them apart? The last hairband is interrupted in female blue-green banded bees (25) but continuous in Murray’s bee (32). Furthermore, the hairy spot on the abdominal point of the females differs in shape. The males are more difficult to tell.

Blue-banded bees only live for about 5 – 6 weeks as an individual, but they have several generations, one following the other. In the lucerne growing areas around Keith, the bees are active from the about mid-October until the end of April. And because they are very common, this means that, whenever the grower decide to shut up the crop to induce flowering between October and February, blue-banded bees will be always be part of the mix!

Next week, we will find out how we know that these bees pollinate lucerne.

 

 

 

 

Lucerne pollination under irrigation

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.

Lasioglossum mu for blog

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. paddock treeMany 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!

Acknowledgeents SA

 

The wild pollinators of lucerne and how to make the most of them

Welcome!

If you want to know what you can do to protect, enhance and future proof free pollination services in your lucerne crop, then this blog is for you.

Over the coming months, bee researcher Dr Katja Hogendoorn, from the University of Adelaide, will give an overview of the most common wild pollinators found in lucerne. Every month, the focus will be on a different group of bees and in weekly blogs, we will explore what they look like, their capacity for lucerne pollination, when they are active, where they nest, what other plants they rely on and what farmers can do to enhance these bees in their crop.

Leafcutter bee collecting pollen on lucerne (photo: Katja Hogendoorn)

 

Why should we care? Because, as explained below, lucerne seed growers benefit substantially from the free pollination services provided by wild pollinators. And because a landscape that provides healthy food for bees allows them to cope better with pests and diseases.

 

 

Wild pollinators  and their importance for lucerne seed production

The value of Australian lucerne seed production was $95 M per year in 2008. The crop relies for 100% on animal pollination. In 2014, a survey  by Lucerne Australia showed that 66% of dryland lucerne growers do not run bees and therefore rely completely on wild pollinators. According to Jenny Aitken, Executive Officer of Lucerne Australia, dryland seed production is highly variable. “In normal years about 30 – 40% of seed is produced on dryland” she says.  Thus, in a normal year, the contribution of wild pollinators lucerne seed production is worth around A$ 20 – 25 M, for dryland lucerne alone.

Value in million $A. During normal years, wild pollinators contribute A$20 – 25 M to dryland lucerne seed production.

These free pollination services are not to be sniffed at! With smart land management, these benefits can be secured and even enhanced. Over the coming weeks we’ll explore the identity and needs of wild lucerne pollinators, so lucerne growers can use the knowledge to their advantage.

Next month we will look at blue-banded bees.

textAcknowledgeents SA

 

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