Axelsen, J. A., Enkegaard, A., Strandberg, B., Kryger, P. & Sørensen, P. B. 2011: Bestøvningsforhold og –behov i dyrkede afgrøder. Danmarks Miljøundersøgelser, Aarhus Universitet, 47 sider – Faglig rapport fra DMU nr. 832, http://www.dmu.dk/Pub/FR832.pdf.

 

Summary

This report is one of three reports prepared for the Danish Ministry of Food, Agriculture and Fisheries (The Danish Plant Directorate) for the project ”Pollination conditions and the requirements for crops and wild plants”. The purpose of this report was to investigate pollination conditions and requirements in cultivated crops.

Several crops are dependent on insect pollination, for which the honey bee is normally considered the most important one. But bumblebees, solitary bees, butterflies and hover flies also play an important role. As far as the area they cover, the most important insect pollinated crops are winter oilseed rape, fruit trees and berry bushes. It is estimated that insect pollination is worth between 421 and 690 million DKK a year in Denmark. Most of this pollination is done in the spring, especially for oilseed rape, fruit trees and berry bushes.

In the spring, oilseed rape, fruit trees and berry bushes are the source of pollen and nectar for both honey bees and other pollinators. However, in order to have good conditions in Denmark, honey- and bumblebees lack good sources of pollen and nectar throughout the summer. White and red clover for seed production are good sources in the middle of summer, just as clover-grass fields should be a good source throughout the summer. However, usually they are not, as the clover in the clover meadows often does not bloom due to numerous cuttings or high grazing pressure. As oilseed rape and fruit crops are mostly located on the islands and in east Jutland, there are not many good sources of nectar and pollen in the southern, western and northern Jutland, which causes the pollinators to be completely dependent on sources of pollen and nectar in gardens, field boundaries, small biotopes and forests. The same conditions apply throughout the summer on the islands, unless there are areas with seed production, especially white and red clover.

Many factors affect the conditions for pollinators in Danish farmland. Among these, crop rotation, herbicides, pest control, ploughing etc. undoubtedly play a part, but the extent of the importance of these factors is unknown.

Possible measures to improve the conditions for pollinators in the farmland could be:

• diversifying the choice of crop in order to ensure that more pollen and nectar be available throughout the spring and summer all over the country.
• diversifying the landscape in order to create a better mosaic of flower-rich habitats in agricultural land.
• improving the quality of live hedges, boundaries, small biotopes and forests in order to create good sources of pollen and nectar for pollinators and nesting sites for bumblebees and solitary bees.
• less efficient weed control.

The following gaps in knowledge are identified:

• how will increasing the pollination capacity (honey bees and wild pollinators) affect production.
• separating the importance of honey bees and wild pollinators.
• to which extent do crops that bloom at the same time compete for pollination services.
• how do we improve conditions for wild pollinators in farmland.
• to which extent do insecticide applications affect pollination.