Small-scale habitat enhancement does not enhance native bee (Hymenoptera: Apoidea) nesting in sunflower fields

On-farm habitat enhancement has been proposed as a management technique that can bolster populations of native crop pollinators, including wild bees. We tested whether small-scale enhancements, specifically field-margin hedgerow plantings, increased the incidence of native bee nesting adjacent to and within hybrid sunflower fields, a pollinator-dependent crop. We also examined whether hedgerows augmented the movement of native bees deeper into fields. We did not find evidence that hedgerows affected either nesting nor bee penetration into crop fields. Hybrid sunflower provides abundant floral resources, while hedgerow plantings affect resources in less than 1% of the study landscape. We suggest that for this crop system, field-margin enhancement may not provide sufficient resources to impact bee nesting and movement in monoculture agriculture.