Pollination of caged hybrid seed red rape with Osmia cornuta and Apis mellifera ( Hymenoptera Megachilidae and Apidae )

Osmia cornuta was tested as a pollinator of caged hybrid red rape for seed production in comparison to A. mellifera. Nine screen cages were set up, each to enclose ten plants of red rape. Four cages were provided with 40 O. cornuta (10 females and 30 males). In each of other four cages a small nucleus (ca. 400 workers) of A. mellifera was introduced. To estimate seed yields without pollinators, no bees were introduced in the ninth cage. After bloom, seed yield, seed germination percentages after 5 and 7 days, and seed weight were measured. Osmia cornuta readily visited red rape flowers, and pollinated them successfully. The O. cornuta cages produced a 1.5-fold increase in seed yield compared to A. mellifera cages. Seed quality was similar in O. cornuta and A. mellifera cages. The “no pollinator” cage produced few seeds, and of low quality. Red rape seems to be a suitable plant on which to rear O. cornuta, since the O. cornuta population released was increased by 1.2-fold.