Nesting Habits of Non-Native and Native Mason Bee Species (Osmia species) in North Georgia Apple Orchards

Mason bees (Osmia species) are known to be efficient and reliable pollinators.  In Georgia, we have documented that mason bees play a particularly valuable pollination role in apple and other early-blooming crops, particularly when fruit tree flowers bloom early in the season.  Since mason bees are one of the first bees to emerge after winter, they are present in good numbers during early blooms, while the traditional native bee pollinators in Georgia, the mining bees (Andrena species), are still overwintering in their burrows.  In order to boost the abundance of mason bees in Georgia apple orchards, we provided target orchards with additional mason bee nesting habitats and floral resources.  In a pilot study in 2013, we found that the most common native bees that used the nesting habitats were Osmia georgica, while the most common introduced (non-native) mason bee was O. taurus.  Georgica preferred 6mm nesting tubes, while taurus preferred 8mm diameter nesting tubes.  In 2014, we placed 24 nesting habitats in 3 different orchards.  Significant differences in nesting behaviors (nesting tube diameter, number of cells per tube, number of eggs laid) were measured between the native mason bee species and the introduced mason bees species.