Many bee pollinators are in decline, and exposure to diseases has been implicated as one of the potential causes Novel work in my lab found that consuming sunflower pollen dramatically reduced bumble bee infection by a gut pathogen. These are excited results, but at this point we have established this effect only in the lab, with a single sunflower variety, one bumble bee species, and one pathogen species. The proposed work would expand upon these findings by (1) ascertaining how widespread the 'medicinal' effect is across sunflowers and related species, (2) determining whether feeding bees sunflower pollen can reduce infection by multiple pathogens in the field, and (3) ascertain how much sunflower pollen is needed in the diet to reduce pathogen infection. Combined, these data will provide comprehensive information that can be used to inform choices about coflowering plants near crops that could help manage bee disease, and may provide options for beekeepers of pollen dietary supplements that directly reduce disease loads.
Define variability of chemically mediated interactions between pests, crops, and beneficial organisms in terms of plant chemistry, species interactions and landscape factors in the Northeast.
Obj 1. I will grow 3 varieties of domesticated sunflower (Helianthus annuus), 2 wild H. annuus accessions, 2 other Helianthus species, and 3 non-Helianthus species from the same family. Taxa will be chosen with guidance from a sunflower phylogeny collaborator to span major clades. Each species will be germinated in the greenhouse and then brought to large field tents at the South Deerfield Agronomy Research Station. Honey bee colonies will be stationed in each tent with pollen traps, to collect pollen that will be used for fall laboratory assays. We will conduct individual-bee assays as we have done previously (Richardson et al. 2015), using buckwheat pollen as a negative control, to evaluate the extent to which pollen from each sunflower taxa reduces Crithidia infection in bumble bees. These will allow us to explore the taxonomic breadth of the diseasereduction capability, pointing towards sunflower clades to evaluate in more depth with greater funding.
2. We will deploy 20 colonies of bumble and/or honey bees at the South Deerfield station. Colonies of each species will be reared with buckwheat or sunflower pollen. After deployment, workers will be sampled twice per colony to assess infection by pathogens including Crithidia, Nosema spp., Apicystis bombi, dicistroviruses, and iflaviruses following methods developed by collaborator Quinn McFrederick (UC Riverside). I will analyze whether pollen type affects presence of each major pathogen and proportion of infected bees at each time point, and colony performance. These data will provide the first field measurements of the potential for pollen to impact colony-level health and disease, including multiple economically important bee species and a range of pathogens.
3. Using our previously established protocols, we will conduct a laboratory assay in which we feed experimentally-infected bumble bees 0, 20%, 40%, 80% or 100% sunflower pollen; the portion that is not sunflower pollen will be buckwheat pollen, which we have found has little impact on Crithidia infection. We will assess infection after one week of feeding, to determine whether there is a linear relationship between the amount of sunflower in the diet and medicinal impact, or if there is a necessary threshold to see reduced infection. These data could be valuable in planning future sunflower plantings to ensure they have the desired impact on bee pathogens.