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Sunday, March 13, 2016

Mushroom superheroes

This week I went to Amherst, Massachusetts to attend the annual conference of the Ecological Landscape Alliance, this year titled, “Sustaining the Living Landscape.” One of the speakers pushing the boundaries of conventional horticulture was Tradd Cotter, who gave the keynote address, “Mycoremediation: Healing Compromised Eco-systems with Fungi.”

    Cotter came across as an obsessed genius and kind of a wild man. He introduced himself by explaining that he had been accepted to train as an Air Force fighter pilot when he decided instead to go into mycology. At Mushroom Mountain, his mushroom farm and research facility in South Carolina, he has developed fungi that can break down toxic chemicals in soil and water.

    As I understood it, the fungal mycelium (the vegetative stage that gathers nutrients, usually out of sight, before creating the mushroom that is its fruiting body) can be “trained” to feed on a particular substrate. 

Oyster mushroom mycelium growing on coffee grounds-photo by Tobi Kellner

Cotter isolates fungal cultures on Petri dishes with substances he wants them to “eat.” When it has no other food, in a few generations the fungus modifies itself genetically to extract nutrition from that substance, which could be a chemical, a microorganism (such as coliform bacteria in sewage), a particular plant, or even an unwanted insect. It breaks down the noxious entity into building blocks that can be useful, for example for soil improvement.

    While fungi in general are opportunistic, some have more potential to develop this capacity to attack specific chemicals and organisms. Interestingly, one of the species Cotter finds most useful is the oyster mushroom, Pleurotus ostreatus, a familiar ingredient in Asian cuisines. 

Oyster mushrooms on a sugar maple-photo by David Spahr
    Cotter put out a call for people to send him problem insects they find that are infected with fungus. He showed a slide of a fire ant covered with white filament. The creepy part: a mushroom eventually grows out of the insect’s brain! When he receives these local ecotypes, or genetically distinct geographical populations, of fungi, he can grow them in his lab and reproduce them for use in the field. This offers a way to reduce use of toxic pesticides.

    I must say that the image of that mushroom growing out of the ant’s head gave me pause. I’ve never been stung by fire ants, but I understand it’s quite unpleasant, so I can understand why a killer fungus would be appealing. The red imported fire ant, Solenopsis invicta, comes from South America and is thought to have been introduced to the US accidentally. With climate change, we can expect it may continue migrating north from humid southern states.

Red imported fire ant-Photograph by David Almquist, University of Florida.

    An audience member suggested we could use a fungus to attack winter moth, Operophtera brumata, a nonnative insect damaging New England trees. 

Birch leaves chewed by winter moth caterpillars
That’s not so different from the work that’s being done releasing insect predators for winter moth. Before those are released, they’re comprehensively tested to make sure they’ll only eat the nonnative insect and won’t go on to disrupt the ecosystem. I’d want the targeted mushrooms to be just as fully screened.

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