Biology, Genetic Diversity, and Conservation of Wild Bees in Tree Fruit Orchards

Simple Summary Honey bees (Apis mellifera) are the most economically important agricultural pollinator in North America, as well as being the most frequently studied bee species. Many agricultural systems, such as fruit tree orchards, benefit from having a diversity of bee species present. In this article, we present information about the types of bees that can be found in orchards and explore their mating behaviors, life cycles, genetic differences, flower preferences, and foraging activities. Many orchard-pollinating bees, including bumble bees (Bombus spp.), mason bees (Osmia spp.), and mining bees (Andrena spp.), are often less studied than honey bees. All bees encounter threats to their health and behavior while out foraging. The impacts and mitigation of these threats are often better understood in honey bees. This review summarizes the current knowledge of these threats to orchard bees' health, identifies gaps in the knowledge, and discusses potential management and conservation practices. Different species of bees provide essential ecosystem services by pollinating various agricultural crops, including tree fruits. Many fruits and nuts depend on insect pollination, primarily by wild and managed bees. In different geographical regions where orchard crops are grown, fruit growers rely on wild bees in the farmscape and use orchard bees as alternative pollinators. Orchard crops such as apples, pears, plums, apricots, etc., are mass-flowering crops and attract many different bee species during their bloom period. Many bee species found in orchards emerge from overwintering as the fruit trees start flowering in spring, and the active duration of these bees aligns very closely with the blooming time of fruit trees. In addition, most of the bees in orchards are short-range foragers and tend to stay close to the fruit crops. However, the importance of orchard bee communities is not well understood, and many challenges in maintaining their populations remain. This comprehensive review paper summarizes the different types of bees commonly found in tree fruit orchards in the fruit-growing regions of the United States, their bio-ecology, and genetic diversity. Additionally, recommendations for the management of orchard bees, different strategies for protecting them from multiple stressors, and providing suitable on-farm nesting and floral resource habitats for propagation and conservation are discussed.