Encouraging bumblebee pollination of your property is a very effective and natural way to increase both yields and crop sizes.
Imported from England to pollinate red clover, the clock has turned full circle - now commercial growers can easily foster their own bumblebee populations, so enjoying the benefits first gained by pastoral farmers over a century ago.
Rivaling Honey Bees
The 1885 liberation of bumblebees 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 bumblebees 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, bumblebees can be encouraged to play a larger part in the pollination of orchard crops, and they are important agents of cross-pollination through their multiple visits to different plants of the same species.
"Population in the field is the maximum the environment can carry at the moment, but from the commercial grower’s point of view there are hardly ever enough bumblebees around to pollinate to the levels they ideally would desire," 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 25 years.
Bumblebees 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 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 Barry Donovan.
Unlike honey bee colonies, those of bumblebees do not survive from year to year - they are established quite independently each spring by the new generation of bumblebee 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 bumblebee populations.
"Commercial orchards or market gardens presently are not good places to find bumblebees because they require this continuity of bloom, right from early spring to the end of summer. Orchards and market gardens are often monocultures - once the crop’s flowering period has finished, no other flowers bloom, as growers often spray or mow the pasture under the trees."
Four species of bumblebees are now established in New Zealand: Bombus terrestris, the large earth bumblebee, 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 bumblebee has a black waist combined with this broad yellow-orange abdominal band. , the large garden bumblebee and Bombus hortorum, the small garden bumblebee both have long tongues and yellow waists. The least common is the short-haired bumblebee, Bombus subterraneus, usually smaller than the other species and generally black or with little yellow colouring and found only around inland Canterbury and Otago.
Location can help separate the species, as B ruderatus is found all over New Zealand (except for Stewart Island), while B. hortorum is found mainly in Canterbury, Otago and Southland although it was recently released in Palmerston North and Marlborough.
Cold weather workers
Bumblebees 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, bumblebees 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. They may also "warm up" for flight by decoupling their wings from the flight muscles, and produce warmth through an action akin to shivering. Even at temperatures below zero, bumblebees may still be flying.
Their durability is very important as far as orchardists or home gardeners are concerned, says 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, bumblebees may well be the only insect pollinators visiting their flowers."
The powerful bumblebee 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.
Tongue length (really the proboscis) differs between the four bumblebees and B. rudereatus and B. hortorum have the longest, ideally suited to flowers with long corolla tubes and nectaries far from the mouth of the flower. B.terresteris, the short-tongued bumblebee, will sometimes steal nectar from these flowers by biting a hole in the corolla tube close to the nectaries. These perforated flowers can still be pollinated and set seed if pollinated in the normal way.
Building Nesting Boxes
Encouraging bumblebee pollination in your garden or orchard long-term means encouraging bumblebee queens to colonise permanent nesting boxes located near your crop.
"Newly-active bumblebee queens are looking for concealed, dry cavities in which to lay their eggs and brood in September/October.
Wooden boxes, 25 x 25 x 25 cm fitted with a removable waterproof lid and a floor three centimetres off the ground are ideal. Drill a smooth-surfaced hole of 2.5 cm diameter on one side just above the floor, and place doubled- over carpet underfelt with the hessian removed inside to provide the bedding."
Successful occupation of the nesting box depends 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. Least successful locations are facing south or placed underneath pine trees.
Continuous Food Source Needed
"Providing continuous food sources is a sure way to attract 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, although these plantings may be dictated by the location."
To encourage bumblebee numbers long-term, the flowering plants in the area should be evaluated and any gaps filled with suitable plants. Bumblebee pollination can also be fostered by buying in viable nest with active queens, and growers will then certainly be able to synchronise bumblebee foraging with the blossom of their crops. If apples bloom in August/September, it may well be only the newly-active founding queens working, as they spend much of their time brooding the first generation and it will be five weeks before workers emerge and begin foraging.
Artificially-reared hives are mainly used to pollinate high value glasshouse crops like tomatoes, and Hastings bumble bee man, Nelson Pomeroy was the first person to raise and use bumblebees like this. He began selling nests of Bombus terrestris in 1991. He said tomatoes, melons capsicum and kiwifruit are all well-pollinated by bumblebees, they can pollinate anything not well pollinated by honey bees, especially if their failure is due to cold.
Another raiser of bumble bees, Rosemary Read says growers wanting to foster bumblebee numbers have already got queen bumblebees on their properties: "It just means growing the right flowering crops to feed them when they wake up, and providing them with nesting boxes." Diversity in flowering plants is really important to foster if growers want to get the best bumblebee numbers, she adds.
Shop for your own Bumble Bee Nesting Box here
Bees, bees and more bees at Badassbees.com
Bumble bees as pollinators: Christchurch bumble bee researcher, Rod Macfarlane, in this 1995 paper, says the value and effectiveness of bumblebees should be compared to honeybees to keep their practical use in perspective.
Bumble Bee Pages : This site is dedicated to bumblebees. It features those found in and around the writer's garden in the north-east of Scotland, but most of the information is common to bumblebees all over the world. Includes a page of FAQs, plus The Yearly Lifecycle of the Bumble-bee Colony, Tongues, Hairs, Combs, Brushes and Other Interesting Bits of the Body, How Can You Help Bumble-bees, Books Information and Links, Bumble-bee Foraging Preferences.