Great resource on native wild bees that help pollinate apples (and other fruits, too, of course!!!).
From the Northeastern IPM center:
Insect pollination is a vital service for agricultural systems, and bees are the most important of all insect pollinators. In the United States alone, the value of pollination services by bees is estimated to be $18 billion, but these services are threatened, and finding alternatives is crucial for long-term pollination success. Eastern orchards have a unique opportunity to simultaneously conserve wild bee populations and to benefit from their contribution to fruit pollination.
This 12-page, full-color guide helps readers identify wild pollinators, provide them with food and habitat, and avoid pesticides that are toxic to them. By encouraging wild bee abundance and diversity, agricultural growers may be able to buffer rising honey bee rental costs while creating an environment that better supports both wild and commercial bees.