Biologists and ecologists have long searched for solutions to a looming challenge for life on Earth: rising death rates among pollinators. Two scientific studies offer a compelling perspective on this issue: plants in the sunflower family (Asteraceae) may hold part of the answer.
Both studies converge on a striking finding: sunflower pollen and closely related pollens cut infections from a common bee parasite by 81% to 94% and substantially boost queen bee production.
The results make it clear: an abundance of sunflowers correlates with reduced prevalence of the dangerous intestinal pathogen Crithidia bombi and lower infection intensities compared with areas with little or no sunflower presence.
In addition, higher sunflower abundance was linked to greater queen production in colonies. It did not, however, affect the prevalence of other detected pathogens.
One of the reports notes that this study demonstrates how a single plant species can influence disease dynamics in foraging bees. Fields rich in sunflowers can be employed as a tool to mitigate a pathogen, boosting reproduction in a bee species that is both common and important to agriculture.
The critical insight lies in the pollen exines, the hard outer coating of pollen grains, which proved as effective at reducing infections as whole sunflower pollen, while the interior chemical metabolites alone showed no such benefit.
The key is physics, not chemistry
The investigation found that bees fed pollen from four of the seven other plants in the Asteraceae family experienced 62% to 92% fewer infections by Crithidia bombi than those fed pollen from other Asteraceae sources.
The authors emphasize the growing recognition of bees as essential pollinators and highlight how stressors such as habitat loss, pesticide exposure, and parasites increasingly threaten their health.
One lingering question was whether the benefits stemmed from the chemical substances in sunflower pollen or from its physical structure. To investigate, the researchers separated the spiny outer layer of the pollen from its core metabolites. They combined the thorny outer layer, with its chemistry removed, with pollen given to one group of bees, while another group received the barkless, wildflower pollen enriched with sunflower metabolites.
Lead author Laura Figueroa, a professor at the University of Massachusetts Amherst, explains that the thorny outer layer of sunflower pollen is the factor reducing infections, not the chemistry. Bees that consumed the thorny sunflower pollen exhibited the same reduced infection pattern as those fed whole sunflower pollen, showing an 87% drop in infections compared with the group that received sunflower metabolites. The conclusion is that the physics of the pollen surface plays the decisive role.
Further, bees fed pollen from ragweed, dandelion, and fennel, all within the sunflower family, demonstrated infection rates similar to those fed sunflowers, reinforcing the physical mechanism behind the observed benefits.
The “apocalypse” of insects
Another key factor for colony health is queen bee production. More queens mean a better chance of gene propagation to subsequent generations, reinforcing a colony’s resilience.
In field trials, researchers placed bumblebee colonies on twenty farms with varying sunflower plantings. After several weeks, they sampled gut pathogens, weighed colonies to gauge development, and counted queens to assess reproductive success.
With greater sunflower abundance, infections declined, and queen bee production rose by about 30% for each substantial increase in sunflower pollen availability, according to Rosemary Malfi, the lead author.
The findings hold significance beyond the science papers. Pollinators drive crops from blueberries to coffee and underpin ecosystems valued at hundreds of billions of euros annually in services. The researchers emphasize that pollinators are essential for a varied, healthy, and nutritious diet.
Despite the promising results, questions remain about why sunflower pollen benefits queen production. It is possible that healthier, disease-free bees invest more energy in reproduction, or that Crithidia bombi hampers learning and foraging, and reducing infection improves food-finding capability.
Lynn Adler, another lead author, stresses that these studies do not solve the insect crisis but offer an encouraging signal: the sunflower family can play a meaningful role in sustaining pollinator health and, by extension, human food systems.
For interested readers, the reference materials include scholarly articles published in reputable journals, which discuss the experiments, results, and potential implications in greater depth.
These studies point toward a practical approach: cultivating sunflower fields to support pollinator health and ecosystem services, a strategy that aligns with agricultural and environmental priorities in North America and beyond.