Government of New Brunswick

The pollination of wild blueberry flowers is the last step before fruit formation. For this to occur, pollen must be deposited on the female (or receiving) part of the flower by a pollinating insect. The flower lasts no more than a few days, and pollination has to occur before the flower deteriorates. Several visits by insects are required to ensure adequate pollination and to achieve a good fruit set. The contribution of wild pollinators is important, but is not always sufficient to guarantee a consistently high yield. The use of honeybee hives is an excellent means of improving the fruit set of the crop. To achieve the best results, it is essential to manage the hives in an optimal fashion. Here are some points to consider in order to optimize hive use:

HIVE NUMBERS:

The number of hives necessary for good pollination depends on the strength of the hives, the size of the field, and the "background" pollination provided by wild bees. As a general rule 2.5 to 5 hives per hectare (1-2 hives per acre) is recommended, though growers have run successful experiments with more. In the state of Maine, some of the industrial-scale growers in large fields with few wild pollinators, do in fact use up to five hives per acre. In these cases, there are two hives per acre present on the fields during the whole bloom period. At mid-bloom, a set of "mobile" hives are introduced at the rate of three hives per acre and removed by the tail end of bloom.

Researchers at the University of Maine have been doing research to determine what bee density is needed to get good pollination, and have developed some useful rules of thumb for determining what is a desirable number of hives for the "flower-rich" fields of that state (Drummond, 1994). This requires finding out how many bees are visiting the fields. On a nice sunny day, ten or more areas of the field should be inspected for the bees visiting blossoms. The wild bees are primarily bumble bees and solitary bees. Bee counts should be made for five minutes and the ten counts should be averaged: at an average of more than 2.4 bees per square meter, additional honeybees may not be necessary; at 2 bees, 1 hive per acre is needed; at 1.3 bees, 2 hives per acre are needed; at 0.6 bees, 4 hives per acre are needed; and 5 hives per acre are needed if no bees are seen.

Even in fields with relatively low flower densities, a stocking rate greater than 2 hives per acre does not appear to saturate the field. With a rate of one hive per acre, a University of Québec reasearch team demonstrated up to five-fold increases in yield with the use of honeybee hives (de Oliveira, 1995). These increases were associated with increases in the per cent of fruit set, and particularly an increase in fruit size, due to a greater number of seeds setting in each fruit. These researchers reported potential revenue increases representing $6 to $ 28 for every dollar invested in honeybee hives (revenue and profit increases would of course depend on the price of berries and the additional harvest cost). One of the most significant observations of this study was the importance of hive strength, with one strong hive being more beneficial than as many as four hives of low strength. For more information on pollination and evaluating hive strength, please consult fact sheets B.1.0 and B.4.0, respectively.

TIMING THE INTRODUCTION OF HIVES:

The introduction of hives should be done between 10 and 20% bloom, which occurs towards the end of the first week of flowering. The goal of placing hives at this time is to encourage the bees to forage on the flowers of wild blueberry plants, rather than on the other types of flowers which are present then. For wild blueberry fields surrounded by forest and not adjacent to other fields, the hives can be put out early, and reports from these types of areas in Québec recommend placement as early as 5% flowering (de Oliveira, personal communication). In situations where there are other wild blueberry fields or other sources of flowers, it is best to wait until 20% flowering before introducing the hives. This situation is often more comfortable for the beekeeper as well, since later introductions will benefit from the likelihood of good weather. Fortunately, the wild bees have been observed to prefer the lower, earlier flowers on the plants, while the honeybees appear to prefer the later flowers which are higher on the plants.

HIVE PLACEMENT:

Ideally, honeybee hives should be placed equidistantly throughout the field in order to obtain uniform pollination. For reasons of practicality, hives are often grouped together, either because they are on pallets or to facilitate the work of the beekeeper and/or the grower. This is especially true if the fields are in relatively isolated areas. When hives are assembled together, they are usually in groups of 10 to 15 hives, with 2.5 m between the hives and 3 m between the rows. In addition, it is necessary to alternate the orientation of the hive openings in order to avoid drift.

Hives should be placed off the ground, and growers may wish to supply pallets, lumber or an old door in order for this to occur. This is because dew collects on the bottom board, and bees have to fan it dry before they leave for pollination. Keeping the hives out of weeds and tall grass is also advisable.

The choice of a location for the hive or hives should be given some thought. The goal is to guide the pollinating force toward the interior of the desired field. It is therefore important to consider what surrounds the field, such as other wild blueberry fields or other flowering crops. If this is the case, the distance between the hives and the competing crop should be increased. The following is a list of recommendations for different situations.

  • Wild blueberry field surrounded by forest.
    In small fields surrounded by forest, without any other source of flowers, place the hives near the forest. For larger fields, direct the hives toward the centre of the field. In both cases, space the groups of hives equidistantly in order to encourage the honeybees to work over the whole area.
  • Wild blueberry fields with strong and constant, predominant winds.
    Honeybees cease to be active in a field if wind speeds reach 30 km/hour. In wild blueberry fields with constant winds, honeybee hives should be placed such that the bees are flying against the wind as they make their way to the crop, and with the wind on their way back to the hive. This will result in a congregation of the hives to one end of the field, but will favour the return of the bees to the hives. Provide shelter where possible, either with trees or an artifical windbreak, and/or locate the hives in a low protected area.
  • Wild blueberry field surrounded by other flower sources (blueberry or other).
    In this case, the hive or hives should be placed at the end of the field which is furthest from the competing flowers, such that the bees need to travel the whole distance of the field to reach them. If competing flower sources are present in every direction, the hives should be grouped more closely and in the centre of the field. In this instance, hive replacement and/or rotation can be useful in reducing the movement of bees to neighbouring fields.

HIVE REPLACEMENT OR ROTATION:

Honeybees that have recently been moved into a field will tend to forage on the closest source, but will gradually increase their foraging distance to 1 km or more within a few days. To ensure that the bees do not drift too far away, two or three growers and beekeepers can collaborate to rotate the hives in order to maximize pollination. The hives are exchanged from one field to another one which is more than 4 to 5 km away, after 4 or 5 days of flight. This will eliminate the established flight pattern of the bees in either hive. The new flight pattern will therefore include greater proportions of the target fields. Hive replacement or rotation incurs labour and transportation costs, and may be affordable in fields where the competition from other flowers is high. If the competing vegetation is negligible, hive replacement or rotation may be neither necessary nor economical.

Bee hives should be moved only with the cooperation of the beekeeper. Rough handling can damage brood, and can even result in loss of the queen. Movement should occur after dark only, when all field bees are in the colony. This prevents weakening of the colony from the loss of foragers.

THE EFFECT OF WIND ON HONEYBEE HIVES:

A site protected by predominant winds, like a wooded area or a natural windbreak, is desirable. This type of site facilitates entry and exit to the hive under unfavourable conditions. In the case in which winds are a problem and the wild blueberry field has no suitable, protected areas, an artificial windbreak can be installed. A snow fence can be very useful to reduce windspeed near the hives. The fence should be sufficiently long to ensure protection of the group of hives, and should be 2 to 3 m high. The hives should be located about 1 meter behind the fence. Refer to factsheet A.4.0 for more information on windbreaks.

THE EFFECT OF SUN ON HONEYBEE HIVES:

When hives are located near a wooded area, they should not be shaded in the morning. If this is the case, locate the hives such that the first rays of the morning sun reach the hive. Heat and light activate foraging by bees, and hives should face south or southeast to ensure this. The earlier the bees start the day, the longer will be the pollination period.

WATER SOURCES NEAR THE HIVE:

Water is essential for survival of the hive. If there is no source of natural water like a spring or a pond, water should be provided near the hive. A barrel, cut in half lengthwise, or even a blueberry harvest box can act as a water reservoir. Pieces of wood or another material which floats should be placed at the surface as a landing pad for the bees, or else they will drown. It is very important to establish water sources before bringing hives to a field.

HIVE PROTECTION:

Wild blueberry fields are most often located very far from residential areas, where large numbers of wild animals live. Many of these can cause damage to honeybee hives.

Skunks, raccoons and bears are among the animals which can devastate a hive. The bear is the most destructive in this respect. A beekeeper should be advised if you see or suspect the presence of these animals with any regularity. Beekeepers can not be expected to maintain an interest in bringing bees to fields in which hives have been destroyed. It is in the grower's best interest to visit the fields regularly, and to warn the beekeeper of any potential or actual destruction. For more information on protection methods, please consult factsheet number B.5.0.

INSECTICIDES:

The use of insecticides should be avoided during flowering, and should never be used in the presence of hives. It contravenes the Apiary Act to spray insecticides when bees are in the field. Hold back on introducing the hives, if an insecticide spraying is expected. The beekeeper must always be warned if an insecticide spraying will be performed, so that appropriate precautions can be taken. Some of these are detailed in factsheet C1.6.0.

CONTRACTS:

A contract between growers and beekeepers can be an advantage in determining the responsibility of each party. The New Brunswick Beekeepers' Assocation has a sample agreement for pollination services.

CONCLUSION:

The use of honeybee hives is not a guarantee of high yields, but rather a form of insurance. Uncontrollable factors will influence the performance of bees. Under these circumstances, it is important to keep an open spirit and continue to recognize the value of honeybees in the pollination of wild blueberries.

References:

Canadian Association of Professional Apiculturists. 1995. A Guide for Managing Bees for Crop Pollination.

Conseil des Productions Végétales du Québec. 1977. Apiculture: Emplacement du rucher et dérive. Agdex 616. 4pp.

De Oliveira, D. 1995. Contribution des insectes pollinisateurs a la mise a fruit et au rendement dans les bleuetieres de la Sagamie. Rapport du project SE-081.

Drummond, F. 1994. Determining bee density. in Wild Blueberry Newsletter (ed. David Yarborough), Univ. of Maine.

Hoopingarner, R.A. and G.D. Waller. 1992. Crop Pollination. In The Hive and the Honey Bee (Joe M. Graham, editor). Dadant & Sons, Illinois.

Jadczak, A. 1993. Placement of Honey Bee Colonies Used for Blueberry Pollination. Univ. of Maine.

Karmo, E.A. 1978. Blueberry Pollination - Problems, Possibilities. Beekeeping Fact sheet 109, NSDA, Nova Scotia, 11pp.

Pacific Northwest Extension. 1984. Evaluating Honey Bee Colonies for Pollination: A Guide for Growers and Beekeepers. Publication 245, 6pp.

Root, A.I. 1993. ABC and XYZ of Bee Culture. A.I. Root Company, Medina, Ohio. 500pp.

Vickery, V.R. 1991. The Honey Bee: A Guide for Beekeepers. Particle Press, Pincourt, Québec, 250pp.

Prepared by: Bernard Savoie, P. Ag., Horticultural Technician; John Argall, Provincial Blueberry Specialist, N.B. Department of Agriculture & Rural Development; and Heather Clay, New Brunswick Beekeepers' Association.
Winter 1996