Chapter 8 Honeybees and crop pollination
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Honeybees of the genus Apis are excellent pollinators. On a single trip, a worker bee may visit as many as several hundred flowers of the same species, a flower fidelity very useful in cross-pollination. Moreover, since a honeybee colony consists of several thousands to several tens of thousands of workers, the number of pollinators readily available is great indeed. The final and most important factor contributing to the usefulness of honeybees as pollinators lies in the fact that A. cerana and A. mellifera being kept for the most part in man-made hives, the beekeeper can move them at any time to areas in need of pollinating insects.
The value of A. mellifera as the most valuable pollinating insect has long been recognized throughout the temperate zone, including parts of temperate Asia. In tropical Asia, however, where the staple diet consists of grains from self- or wind-pollinated plants, the value of honeybees as crop pollinators has received little attention. This is regrettable since many species of tropical fruit trees, vegetables, oilseed crops, and nuts of economic importance can benefit from cross-pollination, and yields may he much improved both quantitatively and qualitatively by pollination services from beekeeping. It is essential that agriculturists in Asia explore these possibilities without further delay.
Migrating honeybee colonies for crop pollination calls for a basic understanding of several points by both beekeepers and growers. Firstly, not all crops require or can benefit by honeybee visits: thus, as already mentioned, most cereal crops are self- or wind-pollinated. Growers must therefore be well aware of the pollination requirements of their crops before making arrangements to obtain bees for pollination services.
Secondly, growers must recognize that it is not always to the advantage of beekeepers to migrate their bees' since not all flowering crop plants secrete enough nectar for bees to collect and convert into extractable quantities of honey, and the honeys obtained from some flowers are not acceptable to consumers. Where one or both of these objections arise, the grower may have to rent bees from the beekeeper for pollination services; only when the beekeeper is assured of a satisfactory honey yield can his services be free of charge.
The effectiveness of honeybees in crop pollination depends on many factors, such as the location of the hives, the attractiveness of the flowers to the bees, and the bees' behaviour in approaching the flowers. Only strong colonies should be used in open-field pollination. Two-storey Langstroth hives are popular for pollinator colonies; the hives should be placed on stands. It is important that the number of colonies needed per unit area be established in advance, for maximum efficiency. This number varies considerably according to the crop: many fruit crops require several strong hives per hectare. To ensure that a large proportion of the flowers are visited, the bees should be moved to the area as soon as blossoming begins or, preferably, just before.
A number of factors can to some extent limit the efficiency of bees as pollinators: competition from nearby flowering plants, such as weeds; colony weaknesses brought about by the effects of pesticides, bee diseases and mismanagement during the pollen flow; and the effects of poor weather, which may prevent the trees from flying. Special emphasis should be placed on the danger of pesticides: while colonies of bees are in the field for pollination, toxic pesticides must not be used in the area, and in this regard, cooperation between growers and beekeepers is of the utmost importance.
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