Many people are finding a shortage of natural pollinators in their gardens, and encouraging bumble bees is resulting in a very efficient and natural way to increase both yields and crop sizes of vegetables, fruit trees, flowers and grasses.
What is a bumble bee?
The bumble bee is a really important bee. A member of the Apidae family, the bumble bee is academically referred to as the genus Bombus, and/or Bombus Terrestris. The bumble bee emerges very early in spring, almost late winter. When the queens come out of hibernation, they will pollinate in much cooler temperatures compared to that of a honey bee.
In fact, the bumble bee will even pollinate on days where it’s drizzly and rainy, making this bee species the perfect pollinator for your bloom on fruit trees through the cooler months.
Imported from England to pollinate red clover, the clock has turned full circle - now commercial growers can easily foster their own bumble bee populations and enjoy the benefits first gained by pastoral farmers over a century ago.
Rivalling the honey bee
The 1885 liberation of bumble bees in Canterbury specifically to pollinate red clover made agricultural history.
It was the first time an insect had been deliberately released to pollinate a particular flower. In many ways bumble bees are superior pollinators to honey bees because their larger, furrier bodies collect more pollen from the stamens and make better contact with the pistils than do honey bees or other insects.
Though specialist pollinators, bumble bees can be encouraged to play a larger part in the pollination of our gardens,orchards and crops - they are important agents of cross-pollination through their multiple visits to different plants of the same species.
Bumble bees rely almost entirely on flowering plants for food and their very existence is dependent on gaining adequate supplies of nectar and pollen, or `bee bread.’ Flowers must be visited frequently with pollen supplying the proteins, while nectar provides the sugar necessary for energy.
“The major reason bumble bee populations are not larger is they don’t always have blooming plants to forage upon, combined with the lack of suitable nesting sites where the fertilised queen can establish a new colony," says entomologist Dr. Barry Donovan, of Donovan Scientific Insect Research. Intrigued by the bee’s industrious yet highly-secretive lifestyle, Dr Donovan has been researching them for the last 30+ years.
Bumble bee nests
Encouraging bumble bee pollination in your garden or orchard long-term means encouraging bumble bee queens to colonise permanent nesting boxes located in your garden or near to your crop. Newly-active bumble bee queens are looking for concealed, dry cavities in which to lay their eggs and brood in.
Successful occupation of bumble bee nesting boxes depend upon correct siting: surrounding terrain should be well-drained, protected from excessive winds, shade or heat, and a site against a tree or building aids the bee’s orientation.
Unlike honey bee colonies, those of bumble bees do not survive from year to year - they are established quite independently each spring by the new generation of bumble bee queens reared during the previous summer. These queens survive the winter by hibernating in the ground, venturing forth from about September when awakened by warm spring days. As soon as they emerge, it is important they find a source of nectar, as inability to find adequate nourishment can drastically reduce field bumble bee populations.
Commercial orchards or market gardens presently are not good places to find bumble bees because they require this continuity of bloom, right from early spring to the end of summer.
Bumble bee nest
Four species of bumble bees are now recognised and established in New Zealand:
Bombus terrestris, the large earth bumble bee, is found all over the country , and is very distinctive through its black waist and broad yellow-orange band across its abdomen, as no other bumble bee has a black waist combined with this broad yellow-orange abdominal band.
Bombus hortorum, the small garden bumble bee both have long tongues and yellow waists.
Bombus subterraneus, the least common is the short-haired bumble bee, usually smaller than the other species and generally black or with little yellow colouring and found only around inland Canterbury and Otago.
Bombus ruderatus, location can help separate the species, as Bombus ruderatus is found all over New Zealand (except for Stewart Island), while Bombus hortorum is found mainly in Canterbury, Otago and Southland although it has been released in Palmerston North and the Marlborough area.
Cold weather workers
Bumble bees work very long hours, foraging from dawn to dusk in search of nectar and pollen even on cold, rainy or foggy days which prevent other insects from flying.
Despite being cold-blooded, bumble bees are able to produce their own body heat chemically and by muscular activity. They maintain a thoracic temperature between 35-40 degrees celsius through enzymes in the flight muscles which break down certain sugars and release energy in the form of heat, and this enzyme is not present in the muscles of honey bees.
Their durability is very important as far as orchardists or home gardeners are concerned, says Dr Barry Donovan: "From early springtime right through to early summer the weather can change dramatically during the day - temperatures can plummet, greatly affecting honey bees, which won’t fly below 10 degrees Celsius. This is especially important for kiwifruit growers during its brief late November flowering period - in a cold, wet season, bumble bees may well be the only insect pollinators visiting their flowers."
The pollination buzz
The powerful bumble bee buzz allows them to "buzz pollinate" the anthers of kiwifruit and other blossoms. The bee rakes up a bunch of anthers, holding them against its body with its leg and "buzzes" them - the hard plates of its exoskeleton vibrates, and the amount of energy transferred from the buzzing bee causes the pollen to literally explode outward, covering the bee in pollen.
Continuous food source
Providing continuous food sources is a sure way to attract bumble bee queens, to provide for her workers and maintain higher populations. The home gardener can plant up areas surrounding the garden or orchard with a wide range of flowering plants, shrubs and trees. Colonies with plenty of food produce around twice as many new queens and 50% more males.
To encourage bumble bee numbers long-term, consider adding several Bumble Bee Nesting Boxes around the garden, providing a suitable habitat for re-emerging queens.
Bumble bee pollination can also be encouraged by introducing a live colony with an active queen. Gardeners and growers can then synchronise bumble bee foraging with the blossom of their garden fruit, vegetables, flowers and crops.
Eg. If your apple trees bloom in August/September, it may well be that only the newly-emerged active queens are working, as they spend much of their time brooding the first generation it maybe be five weeks before workers emerge and begin foraging.
By purchasing a live bumble bee colony, you can synchronise bumble bee pollination at exactly the correct time for your bloom. Fantastic pollinators for tomatoes, melons, capsicum and kiwifruit. Bumble bees, can pollinate anything not well pollinated by honey bees, especially if their failure is due to cold.