CANCELLED - Many Medicinal Monarda Monoterpenes: The effects of Monarda fistulosa monoterpenes on the Crithidia bombi gut pathogen in Bombus impatiens

Background/Question/Methods

Bees are important pollinators that contribute to vital ecosystem services. Yet, many bee populations are currently declining due to a variety of causes including pathogens. Some plants produce floral rewards that can reduce bee pathogens when consumed by the bee. Thymol, a secondary metabolite found in some plant nectar, can reduce the concentration of the bee gut pathogen Crithidia bombi in the common eastern bumble bee (Bombus impatiens). Monarda fistulosa, commonly known as wild bergamot, is a common wildflower that attracts many pollinators including bees. Monarda fistulosa individuals can have different chemical phenotypes (chemotypes), each producing one main monoterpene. One of the most common M. fistulosa chemotypes produces thymol. Other chemotypes of M. fistulosa produce carvacrol, linalool, geraniol, and eucalyptol, which all have unknown effects on C. bombi infection in B. impatiens. Because of their chemical similarity to thymol, we hypothesized that these chemicals would also reduce pathogen infection. To address our hypothesis, we conducted diet assays, feeding infected B. impatiens one of five sucrose solutions containing 10ppm of one monoterpene or a no-monoterpene control for one week, then counted pathogen loads.

Results/Conclusions

We found that thymol, carvacrol, and eucalyptol significantly reduced the concentration of C. bombi in B. impatiens compared to the sucrose control. Geraniol and linalool had intermediate effects that were not significantly different from the control treatment or the other compounds that reduced infection. Therefore, plants with certain monoterpenes in their nectar may be effective in reducing pathogen infection and transmission, and could be used to support pollinator health in native and agricultural ecosystems.