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Pollination of Crops

 

Custom Pollination of Manitoba Crops with Honey Bees:

Recommendations and General Information (rev. 2007)

Honey bee pollination is a critical part of agriculture in Manitoba and throughout the world. In fact, pollination is so important that growers can provide the best agronomic practices and genetic stock, but fall short of a good crop if adequate pollination is not achieved. In Canada, the value of honey bee pollination has been estimated at about 10 times more than the value of the honey and beeswax produced.

Although there are many beneficial wild pollinating insects in Manitoba, good consistent pollination by wild insects often is not possible for a number of reasons, including fluctuations in pollinator populations, weather, and agricultural activities such as habitat disturbance and pesticide spraying. For this reason, the practice of “custom pollination” is necessary, for some crops, in the province.

Custom pollination can be defined as providing pollination services to crop growers, usually at a relatively high stocking rate, for a fee, share of crop harvest, and/or other arrangement, as agreed upon by the custom pollinator/beekeeper and grower, verbally and/or in writing with a pollination contract, with the goal of improving the crop yield or value.

The following recommendations for custom pollination are supported by the Manitoba Beekeepers’ Association (MBA) and represent guidelines that may be used by honey beekeepers and growers in Manitoba. The information is presented to help take advantage of and bring together agricultural resources in the province, and to address common questions about custom pollination with honey bees. Where custom pollination is not sought, these recommendations may not apply.

These recommendations try to take into account any costs incurred by the beekeeper including additional labour, stress to the colonies due to insufficient nectar or pollen, any sacrifice of honey production, particularly when the stocking rate is high or nectar production/access is low, as well as the value of the custom pollination service overall. Survey information on the current practices of Manitoba beekeepers (1999-2006) was also considered for the values of stocking rates and fees for some crops.

In some cases, broad ranges are used for the stocking or fee rate, demonstrating the range of what may be appropriate in a given situation. Beekeepers should consider the benefit of a good bee yard that is accessible and sheltered (close to water etc.), and the value of working with conscientious growers that are familiar with pesticides and their impact on honey bees. In any case, communication between the beekeeper and grower is essential to work in partnership and develop a mutually agreed upon pollination contract.

Side statement - In Manitoba, the average honey production is about 165 lbs/hive, with some commercial operators normally averaging 200-300 lbs/hive, each year. Since the early 1990’s, mites have had a negative impact on colonies, and resulted in increased production costs.

The following table includes information on recommendations for custom pollination with honey bees of a variety of crops in Manitoba. For more information, scroll down or click on the CROP name in the table.

Table: Recommendations for Custom Pollination with Honey Bees in Manitoba

CROP

Stocking
 rate
 hives/ac 1
Fee rate
 

$/hive 2

Nectar
 production
Pollen
 production
Bloom
 period 3
Overall
 dependence
 on insect
 pollination
Estimated
 dependence
 on honey
 bees4*

Comments

Hybrid
 Canola

2.0 – 2.5

$90 – 160

poor to
 good

Y

End of June
 to early
 August

1.00

0.95

Mostly central &
 southwest regions
 where soils are
 well-drained
(ie. sandy)

Borage

0.6 – 1.0

$25 – 50

poor to
 fair

Y

End July to
 early
 September

1.00

0.90

Mostly northwest &
 southwest regions
Birdsfoot
 trefoil (aka
 Trefoil)

0.6 – 1.5

$25 – 50

fair to
 good

Y

End of June
 to early
 August

0.90

0.85

Mostly interlake &
 eastern regions

Red Clover

1.0 – 2.0

$25 – 70

poor to
 good

Y

End of June
 to mid
 August

1.00

0.70

Nectar can be
 difficult for bee to
 access. Must
 consider floral
 competition.

Raspberries

0.7 – 1.3

$40 – 70

fair to
 good

Y

Early June to
 early July

0.90

0.70

Mostly central
 region

Apples

1.0 – 2.0

$50 – 70

fair to
 good

Y

Mid May to
 end of June

1.00

0.90

Southern part of the
 province

Strawberries

0.5 – 1.0

$50 – 80

poor

N

End of May
 to end of
 June

0.10

0.10

Not a strong nectar
 source, and rel. low
 dependence
Blueberries
 (lowbush)

1.0 – 3.0

$40 – 70

fair

Y

Early May to
 early July

1.00

0.85

No commercial
 acreage in the
 province

Buckwheat

0.5 - 1.0

$25 – 50

fair to
 good

Y

End of July
 to end of
 August

0.80

0.65

Nectar only flows in
 the morning until
 early afternoon

1 Increasing the number of hives early in the bloom, and reducing numbers late in the bloom, may be used to address the changing pollination needs of the crop. In many cases it can also help to reduce costs, and free up hives for better use elsewhere.

A “hive” may be defined as a pollination unit with a laying queen, at least 5-6 frames of brood at all stages, and enough bees to cover at least 8 frames. The hive standard should be addressed in the contract - greater standards may be required for crops such as hybrid canola, and compensation may be related to colony strength. Adequate brood is important for the development of the colony, and, by increasing the demand for nectar and pollen, improves the foraging and pollination activity of the hive. The hive may include a single or double brood chamber. It should also contain minimal or nil levels of parasites or disease, as well as sufficient food, including pollen.

2 Compensation for custom pollination services may include fees, crop sharing, and/or other arrangement as agreed upon by the beekeeper and the grower. See figure below regarding compensation considerations.

3 Generally speaking, hives should be put in place when about 10% of the flowers are blooming and removed when 80 - 85% of the flowers have finished blooming. Putting bees out too early may cause them to become accustomed to other nectar sources. Waiting for all flowers to bloom before harvesting may result in earlier seed sets shelling out for some field crops (not fruit crops). Where effective pollination is more difficult, hives may be dispersed in groups in the field; otherwise hives can be setup all together, in one location, at the perimeter of the field. Certain crops may have specific pollination requirements.

4 Estimated dependence (d) numbers were derived mostly from prior studies representing Canada and the U.S. (see “value of honey bee pollination” links below). Where d=0.00, plant visitation by honey bees will not increase production; d=1.00, production is only possible with honey bee pollination.

* Leafcutting bees may also be used to pollinate hybrid canola foundation seed, birdsfoot trefoil, buckwheat, and blueberries.

Compensation for custom pollination with honey bees can be thought of as on a spectrum, where a number of factors are considered.

The custom pollination contract should include the following information: The number of hives needed, the standard to which the hives must meet, the compensation/rental rate, pollination dates, and an assurance that no insecticides will be applied during the pollination period. Damage liability (e.g. in case of vandalism, bee poisoning due to pesticides, accidental flooding, etc.) may also be addressed in the contract. The following link includes a pollination contract that may be used by beekeepers and growers: http://www.honeycouncil.ca/users/folder.asp?FolderID=4894

On the toxicity rating of specific pesticides on honey bees visit:

http://www.gov.mb.ca/agriculture/crops/cropproduction/pdf/gcp2007/insect.pdf (0.68 MB)

(Or google search “manitoba crop protection guide”)

On the value of honey bee pollination in Canada and the U.S. visit:

http://www.honeycouncil.ca/users/folder.asp?FolderID=4673 (Canada)

http://www.masterbeekeeper.org/pdf/pollination.pdf (U.S) (0.93 MB)

“A Guide to Managing Bees for Crop Pollination”:

http://www.capabees.ca/users/getdownload.asp?DownloadID=291 (15.7 MB)


Hybrid Canola

Honey bees are used for the production of hybrid canola seed* under specific contract arrangements with seed companies. In Manitoba, hybrid canola is grown or has been grown in areas with sandy soils in the Central and Southwest regions of the province. Hybrid canola is often irrigated but that’s not necessarily the case in Manitoba where the acreage is relatively small. When using honey bees, the field of hybrid canola should be isolated from regular canola fields by at least 1-2 miles, to avoid cross pollination. This is currently a major challenge given the significant acreage of common canola** throughout the province.

The recommended pollination stocking rate for hybrid canola is around 2.0, up to 3.0, hives per acre. Honey bee hives, or pollination units, should be prepared as per the pollination agreement (eg. number of frames of bees and brood). Feed (eg. syrup or pollen substitute) may be required during the pollination period if the hives, without supers, are light and not building up stores otherwise. Honey production is normally fair to good when there is adequate soil moisture for the plant and warm sunny weather for the foraging bees, and the stocking rate is relatively low; however, when the stocking rate is high, colonies may be stressed significantly due to insufficient nectar or pollen.

Canola variety may also affect honey production. The honey is generally extra white in colour. The sticky pollen is conducive to honey bee dispersal, rather than wind distribution, and must not dry out in order to remain viable to fertilize the flower; too much humidity is detrimental also. The period for hybrid canola pollination is usually around the end of June to the beginning of August.

* Foundation canola seed is produced from breeder seed. When speaking of hybrid canola production, both the breeder and foundation seed will be comprised of separate parental lines (i.e. male and female lines). To produce commercially available hybrid canola seed, the foundation parental lines are planted separately in narrow blocks in the field. Honey bees, or leafcutting bees, are used to pollinate the female plants and seed from the female blocks is harvested for the first generation (F1) hybrid canola seed. Hybrid canola seed is certified and is sold to producers to be grown on farms. In Manitoba and Canada, the improved characteristics of hybrid canola, including higher seed yield, has resulted in a significant increase in hybrid canola acres and an associated decrease in open-pollinated acres.

** Regular canola does not require pollination for production; however, yield improvement due to honey bee pollination is generally 5-10%, which can translate into significant dollars each year with the large acreage in the province.

Borage

Borage is an annual herb that is acre-contracted to growers in Manitoba by Bioriginal Food & Science Corp. in Saskatchewan. The oil from borage seed is a good source of gamma-linolenic acid (GLA). Borage is also called “starflower” because of the shape of the flower. Honey bees are the main pollinators of borage in Manitoba.

Although the plant is self-compatible, pollen transfer between flowers is dependent on insects, mainly honey bees, since pollen ripeness and stigma receptivity do not occur at the same time on a given flower. The majority of borage acres in Manitoba are grown in the Northwest and Southwest regions of the province. The recommended pollination stocking rate for borage is 0.6-1.0 hives per acre. Honey bee colonies, or pollination units, should be prepared as per the pollination agreement. Feed (eg. syrup or pollen supplement) may be required during the pollination period if the hives, without supers, are light and not building up stores otherwise. The honey is generally extra white in colour. Honey production is poor to fair when the growing conditions are good for the plant and there is warm sunny weather for the foraging bees. By some reports, a good honey crop occurs in 1 out of every 5-10 years. The period for borage pollination is usually around late July to the beginning of September which generally follows the canola flow. Bumble bees may also pollinate borage.

Red Clover

Red clover is mostly self-incompatible and good seed production requires pollination. Adequate pollination of red clover can be difficult and seed yield is often variable for a number of reasons particularly related to flower physiology. The red clover flower has a relatively long corolla tube and usually only fills up partially with nectar. As a result, honey bees are often unable to reach the nectar and suck it up with their tongue. This difficulty discourages pollination and encourages foraging on alternative sources where available. Yet research has shown that, when caged on red clover, honey bees consistently increase yields significantly.

Red clover is grown for seed production throughout the province. The recommended pollination stocking rate for red clover is 1.0-2.0 hives per acre. Feed (eg. syrup) may be required during the pollination period if hives (without supers) are light and not building up stores otherwise, honey production must be considered in the pollination agreement. The honey is generally white to light amber in colour. It is believed that honey bees will also visit red clover flowers solely for pollen collection depending on the needs of the colony and the availability of pollen and nectar in the area.

The period for red clover pollination is usually around the end of June to the middle of August. If the weather’s been hot and dry, the honey bees may not be able to pollinate all flowers in this time period before significant seed starts shelling out. In this case, it may make sense to remove the bees and give up some bloom at the end of the season to an earlier harvest. It is believed, however, that hot, dry weather helps the nectar rise in the corolla tube, and therefore provides the best conditions for honey bees to access red clover nectar in the field.

The target red clover field should be visually inspected for honey bees on flowers and signs of pollination. If pollination is adequate, the flower will wilt and droop and turn rusty brown in colour, and the field will appear greenish-brown. Inadequately pollinated fields remain pink in colour.

There are single-cut (SC) and double-cut (DC) varieties of red clover. Most SC varieties are diploid and flower later than DC varieties, while DC varieties flower earlier and are mostly tetraploid. The majority of the red clover in Manitoba is of the DC variety. Altaswede is the main SC variety, while there are a dozen or more DC varieties grown in Canada. Past research found that tetraploid varieties have longer corollas than diploid varieties, and that breeding for a shorter corolla was not viable.

There is little information about the corolla tube length or honey production potential of current varieties. However past research has shown that there may be a significant difference between varieties which can translate into differences in honey production and pollination efficacy. For example, the Altaswede variety of SC red clover has a relatively short corolla tube length, and it has been reported to be well-visited by honey bees in Manitoba.

No clear relationship has been found between honey bee race and compatibility with red clover, although theoretically, bees with a longer tongue should have better access to red clover nectar. Worldwide, the races with the longest tongue are (in descending order) Caucasian, Carniolan and Italian, and although Caucasians have the longest tongue on average, they are not found in Manitoba, whereas Carniolan and Italian bees are very common in the province. Bumble bees have a longer tongue than honey bees and are another option for red clover pollination. Of the dozen or so bumble bee species documented in Manitoba, however, at least one (Bombus terricola) is known to bite through the corolla and “rob” the nectar without pollinating the flowers.

Birdsfoot Trefoil (aka Trefoil)

Birdsfoot trefoil is mostly self-incompatible and seed production is significantly increased with honey bee pollination. Honey bees depress the wing and keel petals to “trip” and pollinate the flower. Each flower can be tripped many times - where one trip results in the production of a large number of seeds and multiple visits (up to 25) maximizes production. Birdsfoot trefoil seed is used in hay and in pastures for feeding livestock such as cattle. Birdsfoot trefoil forage contains proanthocyanidins which reduce problems with bloating in cattle.

Most acres of birdsfoot trefoil are found in the Interlake and Eastern regions of the province. The recommended pollination stocking rate for birdsfoot trefoil is 0.6-1.5 hives per acre. Hives, or pollination units, should be prepared as per the pollination agreement. The honey is generally white in colour. Honey bees also visit birdsfoot trefoil for pollen only. Honey production is fair to good when the growing conditions are good for the plant and there is warm sunny weather for the foraging bees. The period for birdsfoot trefoil pollination is usually around late June to the beginning of August. In some cases, the grower will use leafcutting bees and honey bees in the same field.

Raspberries

Raspberries are largely self-incompatible and honey bee pollination can significantly improve raspberry production quantity and quality. Larger commercial acres are found in the Central region of the province. The recommended pollination stocking rate for raspberries is 0.7-1.3 hives per acre. The honey is generally white in colour. Honey production is fair to good when the growing conditions are good for the plant and there is warm sunny weather for the bees. Very few honey bees visit raspberry flowers to collect pollen only, but research has found that some do. The period for raspberry pollination is usually from early June to early July.

Strawberries

Strawberries are generally self-fertile, and therefore do not require insect pollination for good fruit production; yet it is believed that honey bees can improve strawberry fruit quality. Some studies have shown that honey bees, as well as other insects, may improve fruit set and reduce the number of malformed fruit; however, honey bee pollination is not known to increase yield significantly. Strawberries do not produce a lot of nectar, and although studies have found that honey bees visit flower to collect nectar and/or pollen, in Manitoba honey bees have been found to collect very little or no pollen from strawberries. The variety of strawberry plant may also affect visitation by honey bees.

Apples

Apples are self-incompatible and require insect pollination for fruit production. Honey bees are the main insect pollinators of apples and can significantly increase apple yields as well as improve the quality (eg. symmetry) of the fruit. The recommended pollination stocking rate for apples is 1.0-2.0 hives per acre. There are few apple orchard acres in Manitoba - the majority are located in the Morden area and in the south or southwest part of the province. The honey is generally light amber in colour. Honey production is fair to good when the growing conditions are good for the plant and there is warm sunny weather for the bees to forage.

Blueberries (lowbush)

Currently in Manitoba there are no planted fields or commercially managed wild stands of blueberries. However, there is a small “cottage” industry built around unmanaged lowbush stands. The main species in the northern part of the province is Vaccinium angustifolium and the main species in southern Manitoba is Vaccinium myrtilloides. A number of “half-high” blueberry varieties that were developed out of the University of Minnesota may be suited for commercial production in Manitoba. Highbush blueberries are currently not grown in Manitoba.

Lowbush blueberries are self-incompatible and require insect pollination for fruit production. Honey bees are the main insect pollinators of lowbush blueberries and can significantly increase yields as well as improve the quality of the fruit. The recommended pollination stocking rate for blueberries is 1.0-3.0 hives per acre. Blueberries generally produce a white honey that is well-liked.

Lowbush blueberries are difficult to establish in new fields, but they grow naturally in forest areas that have been cleared, and are burned every second or third year to prevent reforestation and stimulate regrowth. They have very specific soil requirements which greatly limit the areas where they can grow in Manitoba. Blueberries are most commonly found in association with Jack Pine trees, which occur most commonly in the Eastern (eg. the Belair area), Interlake, and Northwest (eg. Swan River area) regions of the province. The soil should be free of large stones, and open, porous soils such as sandy loam or course sands high in organic matter are well suited for blueberry production.

Other Crops

Honey bee pollination is also known to significantly improve the production of other crops such as vegetables and melons (including asparagus, broccoli, carrots, cauliflower, celery, cucumbers, onions, and watermelon).

For small plots, natural pollination may be adequate; however, for larger commercial areas of 5-10 acres or more, managed pollinators such as honey bees should be provided. Stocking rate depends on the crop, and may range from 1-3 hives/acre for some, including asparagus, broccoli, cauliflower, and cucumbers, and more for onions (ie. 5+ hives/acre), which are generally unattractive to bees.

Cicer milkvetch is another crop on which honey bees have bees have been used, at a stocking rate of 0.5-1.5 hives/acre, in the Interlake region - it is not known how much cicer milkvetch is dependent on and benefits from honey bee pollination. Future research is planned to study the impact of honey bee pollination on saskatoons.

The pollination industry in Manitoba is growing, and it is believed that the true value of pollination and the pollinators that provide this service will become more apparent and highly valued!

References:

Free. J.B. 1970. Insect Pollination of Crops. Academic Press. 544 pp.

Scott-Dupree, C. M. Winston, G. Herbert, S.C. Jay, D. Nelson, J. Gates, B. Termeer, G. Otis (editors). 1995. A Guide to Managing Bees for Crop Pollination. Canadian Association of Professional Apiculturists. 34 pp.

Contact Us:

For more information on Custom Pollination of Manitoba Crops with Honey Bees, contact David Ostermann, Pollination Apiarist, Manitoba Agriculture, Food and Rural Initiatives, 204-945-3861.