by Tony Groves, Pam Tyning, and Paul Hausler
Be on the lookout! A non-native aquatic plant called hydrilla (Hydrilla verticillata) is moving north and threatening our lakes and waterways. Hydrilla was imported into Florida as an aquarium plant in the 1950’s. The plant was released into the environment and has since spread to hundreds of waterbodies in over 20 states, including a lake in Indiana just 60 miles south of the Michigan border and a pond in northeast Wisconsin. Hydrilla is extremely fast-growing and tends to form thick mats that can seriously hinder swimming, boating, and fishing. It will often shade out and replace native aquatic plants. When hydrilla becomes over-abundant, imbalances in fish populations can also occur.
Hydrilla is a highly invasive plant that can spread by seed, turions (winter buds), tubers, and plant fragments. Some waterfowl feed on the plant and can spread seeds and tubers into other bodies of water. Tubers and turions can live dormant in the sediment and sustain drought conditions. Fragments of the plant are able to root and grow into new plants. These plant fragments can be transported to new waters via boats and fishing equipment.
Early detection and rapid response is essential to controlling the spread of hydrilla. Several states have implemented control programs in an attempt to halt the spread of the plant. On Lake Manitou, a 735-acre lake in Indiana, the Indiana Department of Natural Resources implemented a quarantine following the discovery of hydrilla in 2006. Both public and private boat ramps were closed and an aggressive multiple-year herbicide treatment program was initiated with the goal of eradicating the plant. The cost of the treatment program may well exceed $2 million dollars.
Remember that a Michigan law was recently enacted that states: "A person shall not place a boat, boating equipment, or boat trailer in the waters of this state if the boat, boating equipment, or boat trailer has an aquatic plant attached."
Hydrilla verticillata. Aquatic plant line drawing is the copyright property of the University of Florida Center for Aquatic Plants (Gainesville). Used with permission.
Hydrilla closely resembles one of our common and beneficial native plants. Elodea, right, is a plant that is native to Michigan. Hydrilla, left, is an exotic plant that, to date, has not been found in any Michigan lakes. If you think you see hydrilla in your lake, contact the Michigan Department of Natural Resources and Environment Office of the Great Lakes at 517-335-4056. For more information, visit www.miseagrant.umich.edu.