The flower, pollination and fertilization
The strawberry (Fragaria x ananassa) flower has 5 white petals, many pistils and styles and 24-36 stamens. It is self-pollinating and produces abundant pollen, deep yellow in color when viable, and nectar that is concentrated in pools at the base of the outermost pistils. The stigmas become receptive before the anthers of the same flower release pollen, encouraging cross-pollination. Pollen is not released until the flower has been open for a while and the anthers have begun to dry. When the drying anthers finally open, pollen bursts from them and scatters across the numerous stigmas. Thus self-pollination is possible.
Once released, pollen stays viable for several days. Pollination is most likely to occur during the first 4 days after the flower opens. The timing of the flower's opening depends on temperature - at low temperature, opening of the anthers and release of pollen is delayed. Pollen viability increases as the temperature increases. Fertilized ovules stimulate the surrounding tissue to begin growing. Those tissues form the strawberry fruit. Incomplete fertilization may bring to misshapen berry. In order to achieve a normal fruit, at least 90% of the ovules must be fertilized. One must also bear in mind that numerous physiological and genetic factors linked to the strawberry variety may also affect the production of normal fruit.

The bumblebee’s visits to the strawberry flowers bring about either self-pollination or cross-pollination. Research of the past few years pointed to the outstanding contribution of the bumblebees to the increase in yield quality and quantity under protected structures.
To receive a perfectly shaped fruit, multiple bee-visits are required. Cross-pollination improves the quality of the strawberry fruit as well.

The hive
Although the strawberry flower contains nectar, it is not always sufficient for the development of the colony. Therefore sugar-water is provided to the hive as a routine.When it leaves the factory, the standard colony for strawberries consists of the founder queen, a few dozen workers, pupae, larvae and eggs. The hive does not contain males. This is a strong colony with an anticipated life expectancy of 5-10 weeks.
 
Introduction scheme
Hives are to be introduced at the start of the bloom at a rate of 5-10 hives per ha. As blossom continues, the dosage may change in accordance with the amount of flowers, due to fluctuations in the strawberry bloom.
In cases of little bloom the amount of hives needs to be reduced. Hives may even be removed due to the danger of over-visitation, which can cause corky scars on the fruit. Over-visitation is usually a rare phenomenon, especially in structures that are heated at night.
It is recommended to use bumblebees in the structure from November until mid-March (depending on temperature and time of planting).
Upon renewal of the normal blossom in spring, it should be considered whether to continue using the bumblebees for pollination, taking into account the destination of the fruit (export or domestic market) and the expected termination of the growing/harvesting period.

Field advisory service
The amount of pollen left in the anthers of the flower is the visual indicator of a bumblebee visit. Empty anthers and pollen scattered on the petals is a sign of an adequate level of bee activity.  Follow-up of the activity of the bees as well as the state of the hives is done in three ways: 1) Direct observation on visiting bumblebees on the flowers. 2) Observation of entries and exits of the worker bees to and from the hive. In a normally functioning colony it is possible to observe a minimum of five entries and exits
during 10 minutes.

The color of the pollen loads on entering bees is yellow. The last two checks should take place during the bee’s peak hours of activity. 3) Checking open flowers for signs of visitation by the bumblebee (see above).