On managing the red mason bee (Osmia bicornis) in apple orchards

A worldwide decline of pollinator abundance is recorded and the worldwide pollination of insect-pollinated crops has traditionally depended on a single species, the honeybee. The risks of relying on a single species are obvious. Other species have been developed for particular crops. Here we present an extension of the framework of Bosch and Kemp (2002) that deals on how to develop a bee species into a crop pollinator. We used nesting aids in different settings to address five important issues that are necessary for an effective management of a bee species in a commercial setting. Our study system was the red mason bee (Osmia bicornis) in apple orchards in eastern Germany, but our approach should be transferable to other settings. The first issue was to demonstrate that it is possible to increase population size of O. bicornis by providing nesting aids. Second, we present how someone can study landscape features that promote the occurrence and abundance of O. bicornis. Further, we studied the dispersal of the species inside the orchard, and could demonstrate that bees prefer to disperse along lines of trees. Finally, we studied the effect of nesting substrate and type of farming on the recruitment of bees. We found a close relationship between the length of nesting tubes and achieved sex ratio and a negative effect of conventional farming on the number of nests built. We conclude with recommendations on how our findings can be used to optimize the management of O. bicornis in apple orchards.