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:
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.
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.