Use of mason bees for pollination in covered organic orchards

Summary

Using mason bees can ensure optimal pollination in intensive fruit orchards when naturally occurring pollinators are not (yet) present or are too few.
Practical recommendations
The two most important managed wild bees for fruit crops pollination are the European orchard bee (Osmia cornuta) and the Red mason bee (Osmia bicornis), both mason bees (life cycle: see Picture 1).
Release mason bees
• Place one or more nesting boxes (Picture 2) on the inner edge and within the orchard (1 m above ground) so that they face the tree rows and can easily reach the flowers, possibly oriented south or southeast.
• Mason bees fly in a perimeter of 50-200 m, so adapt the number and placing of the nesting boxes accordingly. Around 2000 cocoons (2-3 nesting boxes) are needed to pollinate a low-stem fruit orchard of 1 ha.
• Place the overwintered cocoons in the nesting box so they are protected but can also fly out (e.g., a carton box with exit holes).
Where to get mason bees
• Subscription to mason bee rental service (check online if there is a mason bee rental service for your country, e.g., www.pollinature.net), or
• Maintain and propagate mason bees yourself.