Published: 30 Mar 2023
While bumblebees are a feral species, they have proven to be effective pollinators that researchers are keen to learn more about.
First discovered in a garden in the inner Hobart suburb of Sandy Bay in 1992, it is thought the bumblebee arrived from New Zealand. More were soon found in the Tasmanian Botanical Gardens, and the large-bodied pollinator has been a regular visitor to Tasmanian gardens ever since.
Bumblebees are being researched for their potential as alternative pollinators.
To help understand why, Jonathan Finch, an entomologist at the Tasmanian Institute of Agriculture (TIA) explains some of the pros and cons of the alternatives, below.
Jon moved to the University of Tasmania in 2021 from Western Sydney University (WSU), where he worked as a research fellow studying pollination in mango, avocado and strawberry.
His connection to WSU sees him working on a project monitoring bumblebee queens via the use of mini radio backpacks.
“It is early days, the study is still ongoing, but we hope to learn more about how queens forage and choose nesting sites,” Jon said.
By doing this research we hope to learn more about why colonies fail and how we might potentially promote colonies on farms in the future.
Why are alternative pollinators being explored?
There are two main reasons. The first is that we are highly reliant on a single species of pollinator, the introduced European honeybee, to pollinate most of our fruit, nut, and seed crops.
This makes us vulnerable to losses of honeybees due to disease or parasites like the Varroa mite, which is now present on the Australian mainland. Having more pollinator options makes us less vulnerable.
The second reason is the honeybees are not the best pollinator for every crop. For example, bumblebees are excellent pollinators of berries, tomatoes, cucumbers, cherries and more. Having more diverse pollinators may help to improve fruit yields and quality. Honeybees can be in high demand during the Tasmanian flowering season. Having more pollinator options may help to lower the costs of bees for growers.
Aside from potential threats such as Varroa mite, can honeybees’ pollination be improved on?
Yes. We know bumblebees are better suited to pollinating certain flowers than honeybees, delivering more pollen during each visit. Unlike honeybees, bumblebees can be used to pollinate glasshouse crops (this is done extensively overseas) and other forms of protected cropping, such as tunnels.
Honeybees get aggressive in glasshouses and pose a threat to workers. They may also get sick in glasshouses due to the lack of pollen diversity. Beekeepers may therefore be reluctant to rent their hives to glasshouse growers.
Beehives are regularly seen in field crops that need pollinating. How will bumblebees be moved around for pollination?
In Europe and New Zealand, bumblebee hives are purchased annually by growers and placed into orchards and protected cropping environments like glasshouses.
They are relatively cheap (around $150) and are easy to post and move around. Each hive may contain up to 500 workers during the peak of the season before dying off over the winter. They can be temporarily moved and sealed off if spraying is required.
Do bumblebees make honey?
Bumblebees collect and store nectar in their nests like honeybees, but it is considered not economically viable to collect because of the shape of the nest and amount present.
Are there any myths around bumblebees that you would like to bust?
Like honeybees, bumblebees can, and will, sting to defend themselves or the nest. The sting can be more painful than a honeybee. However, bumblebees will almost always prefer to fly away than fight. They are usually much more interested in a flower than they are in you. Generally, they only sting if you try to handle them or disturb the nest.
What are the pros and cons of the alternatives?
- Bumblebees – Excellent pollinators of many crops and fly in cold temperatures when other pollinators don’t, but they may compete with native insects and birds for nectar (e.g., Honeyeaters and Swift parrots). They may also help to spread European weeds like foxglove and Spanish heath. However, evidence for these negative impacts is limited because there have been very few studies.
- Hover flies – Excellent pollinators of many crops and can be reared on cheap and inexpensive materials like cow manure. On the downside, the flies do not return to a nest at night like bees. As such they may leave the crop if they do not have sufficient pollen nectar in and around the crop.
- Mechanical pollination – Has high potential for delivering quality pollen of a known variety to a target crop (i.e., cross pollination). However, the technology is still in its infancy and is likely to have a significant cost in terms of labour, machinery, and pollen. This is especially true when you consider that wild pollinators pollinate crops for free. May be suitable for growers seeking premium quality fruits for export, in which these additional costs may be justified.
- Wild pollinators – Tasmania has 40-plus species of native bee, as well as thousands of other flower-visiting insects including flies, beetle, and butterflies. More research is needed to understand how to support and promote native species on farms, such as providing flower strips and nesting habitat. Native insects will probably never reach high-enough densities to replace bumblebees and honeybees as crop pollinators. However, they may make an important contribution to crop yields as part of the wider pollinator community. As part of our amazing national biodiversity, we should consider ways to protect and promote them on farms for their own sake.