Cherry Pollen and Bee Bread Enhance Fitness of Chaetodactylus hirashimai (Acari: Sarcoptiformes): A Two-Sex Life-Table Evaluation of Four Pollen Diets

The mason bee Osmia excavata Alfken (Hymenoptera: Megachilidae) is an essential pollinator for rosaceous fruit trees in northern China, but its populations are declining because of severe infestations by the mite Chaetodactylus hirashimai Kurosa (Acari: Sarcoptiformes). This mite feeds on pollen within mason bee nest tubes, thereby impairing larval development. However, the effects of different floral resources on the fitness of C. hirashimai remain unclear. Herein, we evaluated the development, survival, and reproduction of C. hirashimai reared on four diets (cherry pollen, cherry bee bread, apple pollen, or apple bee bread), by using an age-stage, two-sex life table. Chaetodactylus hirashimai successfully completed its life cycle on all diets. Cherry pollen supported shorter pre-adult development, longer adult longevity, and higher fecundity than apple pollen. Bee bread diets resulted in significantly lower pre-adult mortality (11.76–14.81%), and higher fecundity (270–278 eggs/female) and net reproductive rate (R0 = 115–120 offspring/individual), than raw pollen (44.64–44.83% mortality; 117–179 eggs/female; R0 = 40–50 offspring/individual). No significant differences in the intrinsic rate of increase (r) and finite rate of increase (λ) were observed among diets. Our findings demonstrated that cherry pollen is a highly favorable resource for C. hirashimai, and bee bread further enhances mite population growth. This study highlights the ecological conflict between cherry pollination and mite infestation, and these life-table results can provide preliminary laboratory support for subsequent research on integrated mite control in fruit orchards.