The use of natural pollination in the greenhouse increases the yield of parthenocarpic cucumbers and it is the most effective way to get a high yield pollinated by bees.
Bee colonies are placed in a greenhouse in a rate of 1 hive per 1000 m2. The hive is placed near the greenhouse walls, otherwise it will be more difficult for bees to find it, and they will run astray. It is recommended to place the hives 2-3 days before the beginning of blossoming. During this time the brood will appear in the family and the bees will become more active.
During application of bees for pollination of cucumber in the greenhouse, it is necessary to monitor the supply of honey and cerago. In a greenhouse with the area of 1000 m2, bees can collect 3-5 g of pollen and 100-150 g of nectar a day, which is not enough for the normal growth and development of the bee family. For a normal existence of a bee family in a nest, there should always be 1-2 kinds of cerago. In winter and spring, one bee family requires 7-9 kg of cerago. From February to May, the bee family spends about 5 kg of cerago. The larger the area of the greenhouse, the better conditions for the development of the bee family.
It is important to note that complete fruit setting occurs when sufficient amount of different pollen enters the style of the female flower, which is possible when one flower is visited by 8-10 bees on the first day of blossoming.
The effectiveness of bee pollination on cucumber decreases at low illumination, so it is important to ensure that it does not fall below 5000 luces. To improve the effectiveness of bees in cloudy weather, there is some practice of training bees with sugar syrup and anise oil. Frames with bees in the nest are sprayed with a solution of sugar and anise oil. Then the cucumber flowers are sprayed in 4-5 rows. Spraying is carried early in the morning and repeated during 4-5 days.
The presence of pesticides smell also affects bees’ activity. It is necessary to make treatments in the afternoon, to prevent the death of bees of pesticides.
In block greenhouses, plants that have grown to the height of gutters make it difficult for the bees to fly to separate parts of the greenhouse, which leads to large losses of bees.
For the pollination of crops in the greenhouse all bee breeds are suitable, but Caucasian honey bees, Ukrainian and Carpathian bees are the best. Caucasian honey bees collect more pollen, work better in cold and cloudy weather, compared to other breeds. They are not aggressive and pollinate the cucumber well, but tend to lose interest in the crop, if some nectariferous plant is blooming outside the greenhouse.
Ukrainian and Carpathian bees have also shown good results in closed ground. They have the same characteristics as the Caucasian honey bees, and also orientate well in the greenhouse.
For pollination of cucumbers in greenhouses growers also use osmia bees. Osmia bees are large, solitary bees that live not in families, but in colonies. They use cut stems of hollow plants (for example, reeds), 12-15 cm long, 1-1.2 cm in diameter in the function of hives. Cut stems must have a knot on one side.
Osmia bees can be removed from diapause for pollination in the greenhouse in winter. Males begin to search for females at temperature of 11-12 ° C, making breeding flights. Two days after mating, the females proceed to collect pollen, the males practically do not take part in pollination. Osmia is capable of pollinating 9-10 flowers per minute and about 4,000 per day. The female lives about 45 days. In the greenhouse, the osmia population is effective during 20-30 days in January-February and 15-20 days in March, 10-15 days in April and 7-10 days in May. Then new batches of incubated bees are introduced into greenhouse.
In comparison with bees, osmia works better when there is a lack of illumination, they are resistant to diseases, do not require feeding, reproduce easily and are transported well.
Bumblebees can effectively be used for pollination of cucumber in greenhouses., Unlike bees, bumblebees pollinate well even in cloudy weather, do not suffer from varroosis, and do not tend to fly long distances from the hive in search of a more attractive meliferous plant.
Bumblebees start to work already at a temperature of 8-9 С. One bumblebee, in comparison with a bee pollinates twice as many flowers per unit of time and carries more pollen on itself. Bumblebee can transfer more pollen to the pistil of the flower than any other pollinator.
Commercial hives make it easy to transport bumblebees, and also collect them inside to move, for example, during chemical treatments.
One bumblebee family works effectively for 1 month, after which its flying-pollinating activity decreases. At the beginning of blooming, 4 hives are exposed in a greenhouse area of 1 hectare and 5 new hives are added every 2 weeks.