Honeybee resistance and tolerance to parasites is affected by the nutrition obtained from floral nectar and pollen. Asteraceae floral rewards have been shown to reduce parasitic infection in many bee species, including honeybees. Researchers in The United States of America hypothesized that the availability of sunflower resources could reduce levels of parasites or pathogens in honeybees at the colony and landscape scale, and hopefully offer sustainable pollinator parasite control.
The researchers tested the effects of sunflower (Helianthus annuus) cropland and pollen supplementation on honeybee resistance to parasites. They used a multi-year, nationwide landscape survey with field and lab experiments to evaluate the effects of sunflower cropland and pollen diets on honeybee infection by micro- and macroparasites, including viruses, Nosema, and Varroa destructor.
Although sunflower had nonsignificant effects on microparasites, they did find that increased sunflower pollen availability correlated with reduced Varroa mite infestation in landscapes and in colonies supplemented with sunflower pollen. Each doubling of sunflower crop area was associated with a 28% reduction in mite infestation, and late-summer supplementation with sunflower pollen reduced mite infestation by 2.75-fold compared to artificial pollen.
The reasons for the association between sunflower and Varroa infestation is uncertain, and further research is needed to determine whether the sunflower has a direct negative effect on mites or if the effects are caused by reductions in honeybee brood production.
Read the full paper:
Palmer-Young, E.C., Malfi, r., Zhou, Y., Joyce, B., Whitehead, H., I Van Wyk, J., Baylis, K., Grubbs, K., Boncristiani, D.L., Evans, J.D., Irwin, R.E., Adler, L.S. (2022) Sunflower-Associated Reductions in Varroa Mite Infestation of Honey Bee Colonies. Journal of Economic Entomology, toac196, https://doi.org/10.1093/jee/toac196