Planting arrangement of blueberry cultivars significantly affects bee behavior, pollen flow, pollination success, and yield

Bees can facilitate cross-pollination in crops by moving pollen between distinct crop plant genotypes, with success dependent on both bee behavior and genotype planting arrangement. Previous research suggests bees forage primarily along crop rows, and deposit pollen relatively close to its source. Combined, this suggests that cross-pollination would be enhanced by mixing plant genotypes within crop rows at relatively fine spatial scales. However, minimal research has explored how bee-mediated pollination is influenced by crop genotype planting design using a manipulative approach. In this study, we created three replicated planting design treatments using potted commercial blueberry plants including 1) single cultivar, 2) mixed cultivars within rows, and 3) mixed cultivars across rows, and stocked the area with managed honey bees and bumble bees. We tracked pollen movement using fluorescent powder, observed bee visitation rates and behaviors, and measured fruit set and yields. We found that bee visitation rates per flower did not differ across planting arrangement treatments. Bumble bees and honey bees showed similar movement and foraging behaviors across treatments.  Fruit set and yield were significantly higher in the mixed cultivar treatments as compared to the single cultivar treatment, but did not differ between mixed cultivar within versus across rows. Cross-pollen deposition was highest in mixed cultivars across rows followed by mixed within rows, and minimal in the single cultivar treatment. Our data show that blueberries benefit from mixing cultivars at fine spatial scales, but there was no strong benefit to mixing within rows as compared to across rows.