During pollination, a bumblebee bites onto the flower and makes the flower vibrate. This is known as buzz pollination. The imprints of the bumblebee's jaw on the flower (bite marks) turn brown within one to four hours and make it possible to check the bumblebees' work. A single visit results in the transfer of enough pollen for pollination. Fruit setting takes place once a flower has been pollinated.
The flower needs to have been pollinated before it closes. Depending on the conditions, a flower will remain open for one to three days. To check on pollination, collect about 20 closed flowers from different spots. All the closed flowers must have bite marks. The closed flowers provide a precise picture of the situation. Flowers that are open for longer than one day have between one and five bite marks
Check the work of the bumblebees at least once every two days. Introduce a new bumblebee hive once the number of bite marks has dropped to just one or two per flower.
Pollen is released best at a relative humidity (RH) of between 50% and 80%. A relative humidity of more than 80%-85% will result in pollen not being released and the bumblebees will become inactive. Below 50% RH, the germination capacity of the pollen decreases, potentially resulting in problems with fruit setting. The bumblebees will still collect pollen, and leave bite marks, but no fruit will grow.
Bumblebees are active at temperatures between 8 and 32 degrees Celsius. Their optimum activity level is at temperatures between 8 and 28 degrees Celsius. At temperatures between 28 and 32 degrees Celsius, their activity level gradually drops. At higher temperatures, the bumblebees stop flying. From the moment, the bumblebees will occupy themselves with cooling the hive until the temperature drops below 32 degrees Celsius again.
A healthy crop and the presence of sufficient healthy flowers form the basis for good pollination. Various factors can disturb the health of the plant and thus also reduce the number of healthy flowers. Potential risks include water shortage, non-balanced nutrition, the influence of viruses, plant diseases, pest infestations, insufficient or extreme growth, extreme climate conditions and the influence of chemicals on the plants or flowers.
Bumblebees maintain a constant temperature in the hive. If the temperature to which they are exposed is too high for a lengthy period, the hive and the colony may suffer damage. You should therefore position the bumblebee hive in the coolest spot, or at least in the shade, particularly during the warmest part of the day. Ensure that the hive gets some sunlight during the dark winter period. Shade can be provided by the crop, a crate, or other screening methods. During periods with extreme temperatures, extra measures will be required such as active cooling.
- Position the hive so that it is easily visible both to the bumblebees and to people
- Ensure the hive is horizontal
- Protect the hive against condensation and rainwater
Not all chemical agents can be combined with bumblebees. Consult the list of side effects, on paper or via the internet, or consult an adviser.
You should preferably not position more than three hives together. Ensure that the hive exits point in different directions but not towards the crop.