Cardboard nesting cavities may promote the development of Osmia cornuta and reduce infestation of kleptoparasitic mites

Mason bees (Osmiaspp.) are receiving increasing attention as they are very effective pollinators of multiple crops. However, different bee-associated kleptoparasites are known which can be detrimental to the development of the bees' offspring. To date, clear evidence-based guidelines to control these kleptoparasites are lacking for growers. This study investigates whether different types of artificial nesting materials-cardboard tubes and wooden grooved boards-influence the development of the European orchard bee (Osmia cornuta) as well as the infestation rate of kleptoparasitic mites in the bees' nest. This preliminary study provides insight that cardboard tubes reduce the infestation rate of mites by 81.8% and as such promote successful development of the European orchard bee by 15.5%. Using cardboard tubes over wooden grooved boards should be advised to growers as an effective management strategy to avoid infestation of kleptoparasitic mites and to enhance successful bee development.