Bee–Fungus Associations
"In summertime, Paul Stamets (D.Sc, Mycologist) has noticed in his garden a continuous convoy of bees from his beehive to his mycelium. This was not a surprising event since in the wild, also, the mycelium and honeybee territories are closely located. But, he thought that the bees might be benefiting from the antiviral properties of those mycelial extracts found naturally near their home. This thought led to scientific lab experiments where he cultured the most aggressive (strong against viruses) mushroom strains and prepared the extracts with which the bees would be fed after. The researchers and he wanted to see if the survival rate of the bees would be affected when they feed the bees with these extracts. Nicolas Naeger(Ph.D. Department of Entomology, Washington State University): “Some of these fungal extracts are really good at reducing viral levels in the bee. So here we have a fungus that is reducing virus levels in an insect”.
Scientists and beekeepers have long studied bees and the microscopic microbes that coexist with them, with a particular emphasis on disease-causing fungi and bacteria found within the bees. Because they can spread quickly and seriously harm entire colonies, entomopathogenic fungi , those that infect and harm insects ,tended to garner the most attention among these disease-causing fungi. For instance, Melissococcus plutonius causes European foulbrood, which can destroy brood and weaken the entire hive, while Ascosphaera apis is well known for producing chalkbrood, a disease that transforms bee larvae into chalky white mummies. Naturally, this piqued the interest of researchers and beekeepers who wanted to better understand these threats in order to create preventative or control measures.
But as research methods improved and scientists used the tools of DNA analysis , they realized that fungi aren't just the bad guys in the story. Actually, a lot of fungi and bees develop intricate relationships, some of which are very advantageous. Some fungi benefit bees by enhancing their nutrition rather than just causing disease. Certain fungi create organic substances that can fend off dangerous microorganisms, giving bees an inherent immune boost. Others appear to support bees' general health or help them manage environmental stressors, suggesting a more complex picture where fungi are not just enemies but also potential allies in the hive ecosystem.
Recent research is demonstrating the true diversity and vibrancy of the fungal communities linked to bees. Yeasts, filamentous fungi, and spores are among them surprisingly, a large number of these fungi are completely harmless. They can be found throughout the hive in a variety of locations, including the bees' bodies, the hive's materials, the bees' gut, and even the surrounding area. For instance, bee bread frequently contains yeasts like Saccharomyces and Candida.
Because bees occasionally find it difficult to obtain all the nutrients they require, particularly when flower sources are scarce or pollen quality varies, fungi are particularly important. The B-complex vitamins, sterols, and amino acids that bees require to remain healthy can be produced by fungi, especially yeasts. According to experiments, bees that are fed spores of beneficial fungi have higher survival rates and stronger immune systems, particularly if their diet is deficient in certain nutrients. This suggests that fungi can serve as dietary supplements, bridging dietary gaps and promoting colony resilience.
The way bees look for food may also be influenced by fungi. Because spores and secretions from fungi frequently have pleasant scents or resemble pollen or nectar, bees appear to be drawn to them. This attraction might encourage them to visit previously unexplored, new fungal-rich locations, such as mushroom beds or decomposing plant matter areas. It's interesting to note that certain fungi, like S. rugoso-annulata, also referred to as the wineskin mushroom, produce compounds that bees eat. This implies that fungi may be a resource that bees value, particularly in periods when conventional food sources are limited, sustaining their colonies through difficult times.
In addition to providing food, fungi seem to help shield bees from illness. Numerous yeasts generate substances that can suppress dangerous bacteria and microorganisms that endanger the well-being of hives. For example, it has been demonstrated that certain strains of Saccharomyces suppress bacteria such as Paenibacillus larvae, which cause American foulbrood, a dangerous disease that affects honeybees. By keeping the hive's microbiome in balance, these beneficial fungi lower the chance of infections. As natural immune boosters, they may also directly boost bees' immune responses, assisting them in more successfully fending off infections.
"Meanwhile, research has shown that the beneficial fungi that exists in the honey bee digestive tract and are used to help ferment pollen into bee bread are adversely affected by standard colony inputs such as high fructose corn syrup, formic acid and oxalic acid.This suggests common hive inputs may adversely affect microbial based biopesticides as well."
Additionally, fungi found in hive materials and pollen that has been stored can act as natural preservatives. They keep bee food safe by competing with harmful microbes for resources, thereby extending its shelf life. Given that climate change alters pollen availability and duration of nectar secretion, this is particularly crucial.
"Fungal communities in stored bee provisions diverge from floral communities over time, likely due to the addition of bee secretions, modifications to the stored food, and/or environmental conditions inside the nest. Provisions are stored in nests often lined with resin, glandular secretions, or other materials that are broadly antimicrobial.These provisions are generally acidic (4–4.5 pH) due to the addition of glucose oxidase by worker bees and the proliferation of lactic acid bacteria, which produce gluconic acid and adds to the antimicrobial nature of these provisions"
Usually, spores on to plants or the surrounding environment are how bees passively pick up fungi. There is evidence, however, that bees actively seek out fungi, perhaps due to their nutrients, enticing smells, or visual cues that mimic pollen grains.Fungi may be an underappreciated but important component of honeybees' diet, as evidenced by observations . This behavior might have developed as a means of diversifying their food sources.
It appears that beneficial fungi could be introduced as dietary supplements for bees. It may even be possible to turn the antimicrobial compounds that some fungi produce into natural remedies for hive diseases, eliminating the need for chemical controls that occasionally result in adverse effects.For example, creating probiotic products with helpful fungi could provide a natural defense against diseases like Nosema, chalkbrood or pests like Varroa mites.
"Studies conducted at Cornell University have found that the entomopathogenic fungi Metarhizium anisopliae and Hirsutella thompsonii, kill Varroa mites when applied to colonies but do little harm to bees due to the fact that bees are meticulous groomers and readily remove the fungi spores from their bodies preventing infection. Researchers found the fungi took at least several days before it became effective on the mites and was active for at least 42 days after application making them not only a potentially safe bio-pesticides, but long lasting ones. This indicates that entomopathogenic fungi do not provide a quick, “flash kill” like so many of today’s commercial Varroa mite controls, rather they suppress pathogens and tend to work relatively slowly to kill mites over time."
Nevertheless, we still don't fully understand the interactions between fungi and bees. To pinpoint the precise fungi involved and their functions, more studies are required. Turning this knowledge into useful tools requires an understanding of how fungi provide benefits, whether through immune support, disease suppression, or nutrition. We approach honeybee health holistically when we see fungi as collaborators rather than enemies.
References
Alaux, C., Ducloz, F., Moritz, R. F., & Siegel, P. B. (2010). Effects of nutrition on the immune capacity of bees. *Biology Letters
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