Japanese Barberry. Photo courtesy of Chris Evans, University of Illinois Extension, via bugwood.org
Hemlock Wooly adelgid. Photo courtesy Connecticut Agricultural Experiment Station Archive
Beech bark disease. Photo courtesy of UMass Extension Landscape, Nursery, and Urban Forestry Program
Garlic mustard, second year flowers. Photo courtesy of David Cappaert, Michigan State University, via bugwood.org
Japanese Knotweed. Photo courtesy of National Park Service
Oak Wilt. Photo courtesy of MSU Extension
Phragmites. Photo by Dan Engel, United States Geological Survey
Milfoil. Photo courtesy Graves Lovell, Alabama Department of Conservation and Natural Resources
THE DIRTY DOZEN Up North’s Least Wanted Invasive Species
By Ross Boissoneau You won’t see them on posters at the post office. But make no mistake, these threats to our fields and forests, lakes and streams are most unwelcome. A huge number of plants, animals, and insects are recognized as nonnative threats to the state. Many of them are even prohibited to own in Michigan. Numerous organizations and governmental agencies are working to identify, control, and/or eradicate these pests while scientists, field workers, and ordinary citizens are using various means — natural, chemical, and mechanical — to address the situation, whether the offender is homegrown or not. “[It’s] those that do damage, not just nonnative. Those that harm human health, the environment, or our ecology,” says Eli Baker, education and outreach specialist at Tip of the Mitt Watershed Council. The following is not meant to be a comprehensive list, as there are many others that could be included (for a complete list, go to www.michigan.gov/invasives). Think of it as the highlights — or maybe the lowlights — of the things we wish weren’t here. INVASIVE PHRAGMITES Introduced via ship ballast in the late 1700s, the plant is now illegal to sell, trade, plant, or share in Michigan. Invasive phragmites can clog wetlands, as their stems and rhizomes catch sediments, eventually filling in small waterways. Its height and thickness can prevent waterfowl from using invaded areas as a home or even a stopping point. With the potential to grow over six feet high, phragmites can make it near
impossible for many native species to access wetlands and they commonly impede the views from waterside properties, as well. PURPLE LOOSESTRIFE Think of it as the near-perfect invader: Introduced from Eurasia via ship ballast and intentionally planted as an ornamental garden flower in the 1800s, the undeniably pretty but deadly purple loosestrife bears seeds that germinate very rapidly and grow faster than almost any other wetland plant. The problem? This cruel beauty — now illegal to sell, trade, plant, or share in Michigan — not only reduces critical food resources for birds, butterflies, and other wild creatures but also boasts stiff stems that collect so much debris, they can entirely dry up shallow waters, destroying the habitat for native aquatic animals that have been living there. NEW ZEALAND MUD SNAIL Joanne Foreman, invasive species communication coordinator for the state’s Department of Natural Resources, Environment, Great Lakes and Energy, and Department of Agriculture and Rural Development, says the New Zealand mud snail is one of the greatest aquatic threats out there: It’s very small, reproduces quickly, and can survive in or out of the water. They eat a lot of the lowest levels on the food chain, but when ingested by fish on the next level, the snails offer no nutritional value and simply pass through the fish. Unfortunately, these snails prefer the same habitat as trout — bad news for anglers looking to catch big, healthy fish. They are currently in the Au Sable, Pere Marquette,
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Boardman, and Manistee Rivers. Even worse, because New Zealand mud snails can survive out of the water, they can be easily transferred on waders, meaning no trout stream is safe. “There’s no magic bullet,” Foreman says. But anglers can help stem spread the by thoroughly cleaning off their waders before moving from one river to another. ZEBRA MUSSELS Some four decades after they first gained a foothold in the Great Lakes, zebra mussels are still causing economic and human health concerns, says Baker. They’ve also moved inland, likely transported by boaters who moved their watercraft from one waterway to another without cleaning off their boats. Lakeshore residents around northern Michigan have reported entire colonies attached to their docks, boat hulls, and water intake pipes. Prolific reproducers, each zebra mussel can filter a liter of water per day, removing almost every microscopic aquatic plant and animal. Not only does this disrupt the food chain, but the resulting clearer water also permits sunlight to penetrate deeper into lakes, resulting in increased growth of rooted aquatic vegetation and bottom-dwelling algae. That said, they are a lower priority than the next member of the Dirty Dozen. QUAGGA MUSSELS Even though Quagga mussels are less common than zebra mussels, Baker says quaggas pose a greater threat; they have a wider distribution and can survive both deeper waters and colder temperatures. Jane Perrino, Aquatic Invasive Species
Coordinator for the Benzie Conservation District, says their ability to adapt makes them particularly formidable. “They can reposition themselves if disturbed, and they don’t need a hard substrate,” she says. “They can settle in on all kinds of surfaces” — sandy lake bottoms included. Good Harbor Reef is a good example. There, quagga mussels have blocked spawning sites for whitefish, lake herring, lake trout, and other native aquatic species. The negative impacts extend to the Sleeping Bear Dunes National Lakeshore, where dead algae and mussel shells are creating a nuisance and a hazard when they wash up on beaches. In addition, the area has experienced problems with the botulism toxin — likely driven by the dead algae invasive mussels have introduced into the food — leading to the death of fish and waterbirds. One of the biggest challenges for both species of mussels and the many other invasives is the cost of addressing them. “What the party [trying to address the problem] is pursuing and how deep their pockets are” are huge factors in the efforts to eradicate mussels, Perino says. EURASIAN WATER MILFOIL Milfoil has invaded countless waterways around the region. Biologist Brian Price, formerly executive director of the Leelanau Conservancy, calls Eurasian water milfoil one of the worst invaders. “It packs a big punch — it can plug navigation, impact recreational values and property values.” Tom Hiatt, president of the Lake Leelanau Lake Association, knows the issue well. LLLA is undertaking a major effort to eradicate
