Interactions between Brassica carinata and its pollinators is shaped by managed beehives and neonicotinoid seed treatment

Brassica carinata is a biofuel and animal feed crop with expanding global production. Although there is much research on common farming practices to improve yield, there is almost a complete absence of data on the dependency of yield through pollination services. Reciprocally, we lack information on whether B. carinata offers ecosystem services to pollinators. We observed almost 4000 pollinator visits, quantified different plant functional traits, including floral resources and examined the effect of supplementing fields with honey bee hives and the use of neonicotinoid seed treatment on seed yield and honey bee health. Data was collected from 35 0.404-ha sites with more than 800 focal B. carinata individuals across 2 years in the Prairie Coteau region of the Northern Great Plains. We found that pollinators (n = 28 species) are attracted to floral resources at different spatial scales. High visitation rates by pollinator species were associated with double the seed set in B. carinata relative to the lowest visitation rates. Brassica carinata adds floral resources to the agricultural ecosystem and therefore has the potential to increase pollinator health. However, species interactions are influenced by the use of insecticides and the presence of honey bees by managed beehives. In particular, insecticides alter the role of pollinators on crop pollination by reducing the positive impact of floral resources on pollinator-mediated yield and honey bee health.