In the College of Forest Resources and Environmental Science (CFRES) forest microbiology lab, a dozen clear glass flasks agitate on a shaker. Each contains small, saffron-yellow gelatinous balls—solid globs of the fungus Chondrostereum purpureum growing in a malt-extract solution.
Abe Stone, propagator of the mycelium, stands nearby, regarding the fresh batch of fungi balls with a satisfied smile.
"Exactly what I wanted to see," he says.
Chondrostereum purpureum—lab nickname SuperPurp, a nod to the TV series Adventure Time—is a weak forest pathogen commonly known as silverleaf disease. Stone developed his unique propagation technique after his former method resulted in metal pans of gloppy mush.
"Abe has interesting lab techniques for growing different types of culture," says Tara Bal, assistant professor of forest health and one of Stone's faculty advisors. "One day he came very excitedly to show me the fungus growing in a new method he found in the literature, which creates these cute little balls of hyphae."
Cultivating SuperPurp in balls makes it easier to process into a sprayable liquid. Stone uses an immersion blender to whir the solution to the proper viscosity, then pours the broth into a garden-variety sprayer used for application in outdoor test areas.
"It's literally mushroom soup," he says.
Stone, an undergraduate majoring in ecology and evolutionary biology, is living proof that you don't have to wait until you graduate to tackle the complex problems facing the world.
SuperPurp is Stone's not-so-secret weapon to beat back two species of invasive buckthorn trees: common buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus). The trees are gaining a foothold across the upper Midwest and altering the character of forests. Stone drills holes into buckthorn trunks and sprays them with the SuperPurp solution to weaken the aggressive invaders.
The overarching goal is to create a practical and accessible herbicide alternative that zaps buckthorn without causing harm to surrounding plants. "Our fungus only goes after woody tree species, and if we can establish that this is a viable alternative for those looking to only affect invasive buckthorn, then we've done exactly what we hoped for," says Stone, who also works closely with Sigrid Resh, CFRES research assistant professor and coordinator of the Keweenaw Invasive Species Management Area.
"My research is focused on alternatives to chemical management of invasive plant species, such as biocontrol with insects, goats—and yes, fungus—as well as proving the efficacy of manual control on invasive knotweed species," says Resh.
Stone says silverleaf disease is a natural infector of trees throughout the northern hemisphere, from Norway to Siberia to the boreal forests of Canada. "It is present on many hardwood trees, but is mostly associated with birch, cherry, alder, and aspen trees," Stone explains. "Typically, it causes an infection that slowly affects the tree, causing a silvering color on the leaves, eventual death of some branches and often the entire tree. It is very much a part of the forest ecosystem and has been around for thousands of years. In its natural state, it only infects trees with significant wounds and wouldn't wipe out an entire forest. It is merely one of the many actors causing our forests to develop into various types of ecosystems."
A Stubborn, Pervasive Midwest Invader
Invasive buckthorn is easy to identify and hard to eradicate. There are two species of concern: common buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus), which appear as woody shrubs or small trees everywhere from residential yards to recreational forests. They tolerate sun and shade, and in winter, they hang on to their berries, which are slightly toxic with laxative properties. Seeds from buckthorn berries remain viable in soil for two to three years, producing profuse seeds and saplings.
Digging up smaller trees is the most effective and environmentally sustainable way to get rid of them. Using a weed wrench helps remove more of the root system to discourage regrowth.
The Keweenaw Invasive Species Management Area has weed wrenches available to borrow. Call or email KISMA at 906-487-1139 or kisma.up@gmail.com for details.
Michigan Technological University is a public research university founded in 1885 in Houghton, Michigan, and is home to nearly 7,500 students from more than 60 countries around the world. Consistently ranked among the best universities in the country for return on investment, Michigan’s flagship technological university offers more than 120 undergraduate and graduate degree programs in science and technology, engineering, computing, forestry, business, health professions, humanities, mathematics, social sciences, and the arts. The rural campus is situated just miles from Lake Superior in Michigan's Upper Peninsula, offering year-round opportunities for outdoor adventure.
