Living on the Lake: Not all AIS live underwater!
To most lakeshore property owners, Eurasian water-milfoil is the poster child of aquatic invasive species (AIS) and takes center stage. It colonizes aggressively, hinders boating and fishing, and can make our favorite lake a dense, green jungle of vegetation. Eurasian water-milfoil is an example of a non-native submerged aquatic plant (having stems and leaves growing underwater). In addition to submerged AIS, many of our lakeshores and wetlands are threatened by emergent AIS. Emergent AIS are those plants that are non-native and have roots in the lake bottom or wetland with stems and/or leaves that extend above the water. Many people are very familiar with purple loosestrife, one of our more notable emergent AIS, but there are other, less notable species that are invading and changing our wetlands before our very eyes!
Entering stage left, Iris pseudacorus, commonly called yellow flag. Yellow flag iris has been documented in 20 counties in Wisconsin (www.botany.wisc.edu/herbarium). This plant species is non-native in the U.S. and is thought to have been introduced as an ornamental for ponds and wetlands because of its showiness and size. This iris has also been used in sewage treatment facilities to help remove metals from wastewater and to help trap sediment in the wastewater system. Unfortunately, some of these traits have caused issues when the plant has escaped cultivation. For example, because of its size and its aggressiveness, other native wetland plant species are often outcompeted and displaced. The plant’s ability to trap sediment can also negatively affect the dynamics of some water ecosystems. A study done in Montana showed that yellow flag iris reduced stream width by up to 10 inches per year!
In Oneida County, yellow flag inhabits the Minocqua Thoroughfare and can be easily seen while traveling along Hwy. 47. When I became the AIS coordinator for Oneida County, I was quite unfamiliar with our invasive yellow iris. While Eurasian water-milfoil, curly-leaf pondweed and purple loosestrife demanded attention and stole the show, the beautiful yellow flags silently marched on in our wetlands. They slowly spread their rhizomes outward, creating dense mats that reduce our beautiful native blue flag iris and other wonderful wetland plant species. Yellow flags can also reduce habitat for our waterfowl (displacing sedges and rushes) and fish, cause gastroenteritis in cattle, and their sap can cause skin irritation to humans (in fact, all portions of the plant are poisonous to humans).
In 2013, the yellow flag stand on Hwy. 47 will see management action. Our AIS team will begin hand removal of the outlying plants, and will work toward the most heavily infested areas. When hand removing this species, care must be taken in keeping exposed skin away from plant parts and to keep the rhizomes from fragmenting into multiple pieces (each escaped piece may start a new plant). The area will be mapped prior to management action and will continue to receive periodic monitoring to observe density levels. It is hoped that with hand removal and minimal yearly maintenance, this beautiful wetland complex can once again be free of yellow!
Not all emergent AIS are as showy and flashy as the yellow flag iris. A perfect example of this is Butomus umbellautus, flowering rush. This plant typically goes unnoticed when it isn’t blooming, mimicking and blending in with our native sedges. It has stiff, narrow, triangular leaves and can reach a height of three feet. In mid-summer it sends up flowering stalks that have a spray of white, purple or pink flowers. Admittedly, the plant is beautiful and distinctive when in bloom, but as with many AIS, beauty often hides more sinister characteristics.
Both flowering rush and yellow flag iris spread primarily by rhizomes, which are fleshy underground stems. In addition, flowering rush can also form bulblets on its flowers and roots. These bulblets can be easily dispersed by muskrats, ice movement, water currents and humans. For these reasons, control of flowering rush can be challenging at best. Once this species moves into a water body, it slowly begins to displace native vegetation and can change the physical and ecological aspects of a lake or river. Changes in lake vegetation can reduce fish-spawning habitat for crappies, blue-gills and even walleyes!
In Wisconsin, 10 counties have documented stands of flowering rush. In Oneida County, this species can be seen growing in multiple locations on the Minocqua Chain. The most recent sighting was reported at the Kawaguesaga dam, adjacent to Dam Rd. Due to its tenacious ability to vegetatively reproduce, management and control of flowering rush can be difficult. The narrow leaves of this species tend to easily wash away herbicidal treatments (and often have no effect on the rhizomes), hand-pulling may spread fragments of the plant and there is no biocontrol method to help slow the spread of this aquatic invasive. What have shown promise are cultural control methods. It has been observed that flowering rush will quickly fill in areas lacking other aquatic plants, but moves very slowly if it encounters healthy populations of native species. In other words, promoting and preserving our native aquatic vegetation will slow the spread of this invasive!
As an individual, it may seem daunting to prevent and/or slow the spread of aquatic invasive species. I hear many people ask, “I am only one person, how can I possibly make a difference!?” In reality, it is the many small and individual actions that we take that will help slow the alien invasion! What actions can you take?
• Do not release! water garden plants into the wild.
• Report! suspicious plant behavior to your local lake association, county or state resource managers or even a neighbor. We want to hear from you!
• Volunteer! Local non-profit groups are always looking for help. Throughout the year the Oneida County AIS program has numerous projects that we need help with. Want to help raise beetles, manage aquatic invasive species stands, or monitor for invasive or native plants or animals? We want you!
• Speak out! Don’t be shy about spreading the word on invasive species. Who knows, it may be your tip that saves a lake from a Eurasian water-milfoil invasion! Be a hero, talk to your neighbor.
Michele Sadauskas is the Oneida County AIS Coordinator and can be reached at (715) 365-2750 or [email protected]. Please contact her to arrange AIS presentations and/or workshops, report any suspicious plant behavior, or find out more about any of the above mentioned projects. She welcomes all questions.