THE IMPORTANCE OF BEES IN POLLINATION AND EXPLOITATION OF FRUIT CROPS AND OTHER PLANT SPECIES

Abstract

which, depending on the species, offer plenty of pollen and nectar, and some other elements of bee pasture resin, and a secondary product, honeydew. With a decrease in the intensity of the flowering of fruit crop, the primacy in bee nutrition is slowly taken over by acacia and lime pastures. A large number of tests and experiments, carried out on the territory of Serbia, especially in orchards mechanically isolated from other pollinators, established that the introduction of honeybee and solitary bee colonies greatly enhances the yield and quality of fruits per hectare of plantation. The most pronounced impact of bees is on fruit crops from the rose family (Rosaceae). Fruit pastures consisting primarily of the species within the genera Prunus and Malus, offer plenty of nectar and pollen. The attractiveness of pear flowers (Pyrus domestica), due to the presence of caprylic acid in the nectar, was considerably smaller, so in order to increase crop yields, honeybees must be specially trained. Because of the long flowering season (May September) and/or the abundance of pollen and nectar, blackberries (Rubus fruticosus), strawberries (Fragaria vesca), raspberries (Rubus idaeus) and chestnut (Castanea sativa) become a backup food source for bees which is more extensively exploited during pasture rest periods whereas on large plantations, or areas under crops, they are used as the main pasture. The most widespread pollinators of cultivated flowering plants are honeybees, belonging to the genus Apis. Some 75-90% of fruit orchards in Serbia are pollinated by Apis mellifera. Fruit crop pollination is assisted by strong colonies, with adult bees in 8 out of 10 beehive frames and 5 brood frames, i.e. some 20.000 to 32.000 adult bees. Hives intended for pollination are transported to the site at the beginning of the flowering season (when 15-20% flowers open) when the danger of a change in orientation onto a different nearby culture can be avoided. If transported later, the effects of pollination will be reduced. Hives are preferably arranged in zigzag lines, in groups of 10-15, and on flight paths. In an apple orchard, the hives should be 180-270 m away from each other and left there when 10-15% flowers have blossomed. In order to facilitate pollination of other fruit species, an adequate number of hives per hectare are necessary to be provided and the following is suggested: almonds 5-8, apples (depending on the cultivation method) 2-7, apricots 3, blueberries 7-10, nectarines 2-3, peaches 2-3, pears 2-3, plums 2-3, raspberries 3-4, strawberries 3-8, watermelons 2-7. It is known that many flowering plants are efficiently pollinated only by certain insect species so, in order to find and use the most efficient pollinators, domestication of insects is resorted to. Encouraged by successful domestication, orchard bee species used today are: Osmia lignaria, 0. rufa and 0. cornuta. Around 500-600 0. cornifrons females or about 600-1800 0. lignaria ones are enough to pollinate 1 ha of apple orchard. To pollinate the same area, 2-6 honeybee hives, with thousands of bees, are required. The advantage of Osmia bees over honeybees as pollinators is that they fly and visit flowers at much lower temperatures (9-11 degrees C) which is what honeybees do not do (they do not fly out at temperatures below 13 degrees C). They fly and pollinate in inclement weather in early spring when temperatures are hostile for the activities of honeybees. 0. cornuta are easily grown and reproduced, they do not share common diseases or parasites with honeybees. Their maintenance does not require great investments. Using such bees to pollinate orchards results in high-quality crops, increased fruit production by 30%, that is almost unachievable by any other agrotechnical measures, and also in reduced costs of orchard maintenance. However, in new plantations, with hail nets, best results are achieved by combining solitary bees and honeybees. Bumblebees (Bombus spp.) have proven to be excellent for indoor pollination, and at low temperatures, which is why they can be exploited on plantations with high intensity management and anti-hail protection systems. Planned bee pollination can significantly mitigate, or even neutralize, the loss of fertile flowers due to winterkill, the damage caused by sudden drying of branches and twigs, or the appearance of the so-called defective flowers, or premature rejection of flower buds and incomplete flowering, as well as the losses brought on by cold and strong winds. Planned pollination shortens the flowering season, which lowers the risk of infestation through the flower, and also reduces the use of pesticides. A planned organization and removal of colonies of pollinating insects may have effect on yield and can help avoid crop thinning, which significantly reduces production costs. Planned pollination, therefore, provides more reliable fruit growing, better quality products and also increases production efficiency.