Bees have a surprising hero.
Vicious Varroa destructor mites feed off bees and weaken them, aggravating an already critical situation for pollinators. Chemical pesticides have been used to control the mites, but the parasites are starting to develop resistance to them.
Enter the fungus.
Metarhizium, a common mold-like fungus found in soil around the world, has spores that attack and kill Varroa mites. The spores are safe for bees, making fungal treatment a viable option.
Fungi have emerged as a potential alternative for a vast range of uses. In years past, molds brought us penicillin and blue cheese. Now, mycelium—the rootlike tendrils under many fungi—is fashioned into biodegradable packaging, strong and fire-resistant building materials, and even hats and other clothes.
More than just delicious mushrooms, fungi have powerful abilities to break down plant waste, or even polyurethane and petroleum by-products. They can grow into strong materials at a tremendous rate, have medicinal properties, and keep ecosystems functioning.
Washington State University researchers are taking full advantage of those unique properties. Entomologists have developed Metarhizium to survive beehive temperatures and wipe out Varroa mites. Researchers are experimenting with feeding fungal extracts to bees, and one fungi-phile WSU student has even started constructing biodegradable bee hotels from mycelium.
Other WSU researchers study microscopic fungi in the soil to help plants take up nutrients, alleviating the need for as many chemical fertilizers. And, in partnership with Pacific Northwest National Laboratory (PNNL), engineers look to mimic and improve on a rot fungus that breaks down wood, a step toward more biofuel production.
Often unseen yet crucial for our ecosystems, fungi are proving to be heros not only to the bees but perhaps to the world.
Mycologist and fungi enthusiast Paul Stamets, co-owner and founder of Olympia-based business Fungi Perfecti, develops fungi into applications ranging from medicine to biocontrol to habitat restoration. Stamets has also worked on projects that show antiviral properties of mycelium extracts in people.
When he saw bees feeding on mushrooms, and knowing that bee health is crucial for pollination, Stamets connected with Steve Sheppard, a professor in WSU’s Department of Entomology. Together, they developed a medicinal extract of mycelium that combats viruses in bees.
The bees face a major crisis, though. Parasitic Varroa mites suck fluids from bees, weakening bees’ immune systems and making them vulnerable to viruses.
“We say that usually without intervention the mites will kill a colony in about two years,” Sheppard says.
Chemical pesticides have been used for many years to control the mites, but the parasites’ rapid life cycle enables them to develop resistance pretty quickly. Beekeepers in the United States now have very limited chemical treatments to control the mites. “There’s a feeling of being near the end of the road there,” Sheppard says.
To make matters worse, colony collapse disorder accelerated around 2008, causing beekeepers to lose up to 50 percent of their hives. Although multiple factors cause bees in a colony to die, scientists found mites were deadlier than they used to be. They had formed a symbiosis with a virus that suppressed bees’ immune system.
“Colony health went from bad to really dismal,” Sheppard says. “It was difficult to keep bees alive.”
Metarhizium spores were already known to destroy mites, almost as well as chemical controls. The spores germinate on the exoskeletons of mites, drill in, and kill the parasites, while honeybees are immune to the spores.
However, the fungal approach had not been explored much because Metarhizium couldn’t survive the high temperatures inside a beehive, around 95 degrees Fahrenheit.
With support from Stamets, Sheppard and the WSU research team of Jennifer Han, Nicholas Naeger, and Brandon Hopkins began a breeding program in 2016 to develop a strain of Metarhizium that could tolerate the heat.
Han, who led the effort, says the team uses other stresses on the fungus to build protection against heat. “We basically grew it on no food or very little food with the idea that if you stress out a fungus for one abiotic aspect, it can help cross-protect against others. So if it is stressed out nutritionally, it can help cross-protect against heat stress,” she says.
Han and the team also screened for virulence against the mites, going through tens of thousands of Metarhizium strains to identify one that was thermal tolerant and deadly to mites. “The term we like to use is directed evolution,” Han says.
Eventually the team developed a strain of the fungus that could survive the heat and kill off most of the mites.
Stamets, who contributed to the 2021 paper, was impressed by the WSU scientists’ success with fungi in helping bees. “It’s providing a real one-two punch, using two different fungi to help bees fight Varroa,” he told WSU News. “The extracts help bee immune systems reduce virus counts while the Metarhizium is a potentially great mite biocontrol agent.”
Naeger says the next step is to commercialize the strain. “We need to get this from the lab to the hands of beekeepers in an actual product that can be used,” he says.
For that to happen, Naeger says they’ll figure out correct dosages, timing of application, and delivery methods, then approach the Environmental Protection Agency for approval.
Since Metarhizium is sustainable and ecologically safer as a biocontrol agent, there’s also interest in its use for pests in other high-value greenhouse crops and organic agriculture. “I think that’s one of the most innovative parts, to develop a biocontrol agent that you’re constantly maintaining its viability, generation after generation,” Sheppard says.
During the research, entomologists found another ally in Katy Ayers, a WSU junior in bioengineering.
Ayers is a fungi superfan. Before transferring to WSU from Nebraska, Ayers built the world’s largest canoe made of fungus, an eight-foot, buoyant vessel of mycelium. She grew the canoe for a state fair sustainability award, and it’s still on display at the Nebraska State Fair.
“Not everybody gets interested in fungi. Most people don’t even know about it,” Ayers says. After she watched Super Fungi, a documentary featuring Stamets, she built her world-record mycelium canoe in 2019 and the fungus only took a week to grow into the shape.
Ayers also started another mycelium project in Nebraska: bee homes.
Homes for bees need to be cleaned extensively to prevent diseases and contamination. Mycelium bee homes are biodegradable, so they can be tilled into soil after use. Ayers and a partner successfully tested almost 40 of the mycelium structures.
She says a main reason she transferred to WSU was the work with fungi and bees. Ayers connected with Naeger and the other researchers to continue her work on bee homes.
With assistance from a Scott and Linda Carson Undergraduate Research Excellence Award, Ayers grows bee hotels from mycelium that incorporate the extracts created by Sheppard and Stamets for improving bee health. The bee hotels have tiny holes for solitary bees that specialize in pollinating specific plants.
Ayers has a lot of future fungus plans. She sees potential for mycelium fishing bobbers to replace plastic ones and hunting blinds that can eventually degrade into the soil if left in the woods.
These fungus-related projects give her a sense of accomplishment in helping the planet. “I used to feel really powerless, but fungi—they make me feel powerful,” Ayers says. “Fungi are really our friends. They’re here to help us.”
Tanya Cheeke knows fungi are a powerful asset, particularly for plant health. An assistant professor of microbial ecology at WSU Tri-Cities, Cheeke researches ecology and evolution of plant-microbial interactions.
Some of her recent work looks at mycorrhizal fungi and their role in plant health, particularly for wine grapes in Washington state.
Mycorrhizal fungi thrive on plant roots, where the microscopic organisms extract nutrients from soil and provide them to plants in a symbiotic exchange for carbon. The fungi require carbon to survive.
Based on this relationship, Cheeke examines which mycorrhizal fungi will be most beneficial to plants. She works with a group of symbiotic soil fungi called arbuscular mycorrhiza.
“They’re thought to be one of the most ancient symbioses with plants on earth,” Cheeke says. “There are fossils dating back at least 400 million years.”
Not only do plants thrive because of the mycorrhizal relationship, the carbon taken in by fungi—up to 5 billion tons annually—would otherwise be released into the atmosphere as carbon dioxide, aggravating climate change with more greenhouse gasses.
Still, more research is needed to understand the full extent of the fungi role in soil and plant health. For example, Cheeke notes that under high-nutrient conditions, such as when fertilizer is added to soil, mycorrhizal fungi can become a carbon cost on the plant and take more than they return in nutrients.
It’s a complex system. Cheeke and her research team, including her collaborator, Extension assistant professor and viticulture expert Michelle Moyer, have even seen significant differences between merlot and chardonnay grapes in reactions to mycorrhizal treatments. A long-term goal is to find the right types and amounts of the fungi to support different plants.
“You could potentially reduce fertilizer use by cultivating certain types of mycorrhizal fungi in the soil,” she notes. “If we can identify certain plant-fungal combinations that are beneficial in certain environmental conditions, we can perhaps identify some drought-tolerant fungi or locally adapted fungi that we could add back.”
Cheeke’s investigation extends to ecosystems beyond agriculture, including Palouse Prairie restoration. Soil fungi are “important in both natural and agro-ecosystems, in terms of helping to improve nutrient and water uptake,” Cheeke says. “They can provide protection against pathogens, drought, stress, all sorts of different things.”
Fungi not only build up plants; they’re extraordinarily effective at tearing them down. A rotting tree on a forest floor shows the effectiveness of fungi, such as white rot fungus, in breaking down wood.
Even though that process takes quite a while, it offers a model to tap into one of the best ingredients for biofuel. Lignin forms the cell walls in plants and is the second most abundant carbon source on the planet, but it has tough molecular bonds. Chemists have attempted to efficiently make valuable products from lignin for a century without success.
Xiao Zhang, a professor of chemical engineering at the WSU Voiland School of Chemical Engineering and Bioengineering with a joint appointment with PNNL, worked with his colleague Chun-Long Chen to create a nature-mimicking enzyme, one that improves on fungal mechanisms of breaking down lignin.
Natural enzymes, like those in fungi, are much more benign than chemical methods that require high heat and consume more energy than they produce. However, fungal and bacterial enzymes degrade over time, and they’re too expensive for industrial use.
Chen and Zhang’s team recognized the shortcomings of natural enzymes and used protein-like peptoids as a scaffold to surround the enzyme.
“The side chain of peptoids can carry and enhance the fungal enzyme,” says Zhang.
Chen, a senior research scientist at PNNL and an affiliate professor in chemical engineering and chemistry at the University of Washington, brought his peptoid expertise to the project. Peptoids mimic the function of proteins and, in this case, self-assemble into nanoscale tubes to provide higher stability and more tunable and active surfaces than natural enzymes.
The new stable enzyme survives much higher temperatures than a natural enzyme, which can increase the speed of degrading the lignin. The results were published in a recent issue of Nature Communications.
The biomimetic enzyme is a breakthrough in the effort to digest lignin and make compounds for airplane biofuels and other uses. Zhang and Chen now want to scale up the process and enhance its reactivity.
The world could see even more breakthroughs, from cleaning up waste to building sustainable products, as we begin to dig into the underappreciated abilities of fungi.
“Fungi are the forgotten kingdom on the planet,” Sheppard says. “They are a vastly underutilized, untapped resource. There is little reason not to tap this potential and try to make the world better.”
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Unearthing the Secret Superpowers of Fungus (New York Times, July 27, 2022)
Are Mushrooms the Future of Alternative Leather? (New York Times, Dec. 14, 2022)
WSU’s new bee lab (The Spokesman-Review, Oct. 30, 2022)
The Fungal Evangelist Who Would Save the Bees (Nautilus, Sept. 23, 2020)
Six ways mushrooms can save the world (Paul Stamets TED Talk video)
The World Wood Web: How Fungi Supports Communication Between Plants (Jefferson County Master Gardeners, February 2016)
Video: Katy Ayers and her MyConoe (world record mycelium canoe)
Your Final Resting Place Could Be a Coffin Made of Mushrooms (Wired, July 26, 2022)
WSU researchers make jet fuel compound from fungus (KOMO News, 2015)