A crop of water weeds with the potential to tangle lakes throughout Oakland County and the rest of the state has Michigan wildlife officials asking for help finding the aquatic invaders.
Early detection and monitoring of invasive species can help stop the spread of foreign plants before they take root and become established in a lake. That’s the logic behind a collaborative effort between the Michigan Department of Natural Resources (DNR) and the Michigan Natural Features Inventory (MNFI) that resulted in the DNR’s Early Detection Rapid Response Program, which aims to locate and eradicate several priority aquatic invasive species.
Now in its second year of operation, a field crew with the program has set out to verify reported sightings of aquatic invasive plants at 74 locations in the state. Among those verified were four lakes in Oakland County where invasive plants have started to take hold.
“Oakland County is probably the most active area,” said Matt Ankney, coordinator for the DNR’s Early Detection Rapid Response program.
Ankney said four of the eight plants being targeted by the program have been confirmed in Oakland County, including flowering rush, water hyacinth, water lettuce, and European frog-bit.
“There are four lakes in Oakland County with flowering rush,” Ankney said. “In general, it’s an emergent plant that grows near the shoreline. It has been in Michigan for a few decades. We have seen it for a fair amount of time — the rapid response (classification) is because we are starting to see it accelerate.”
Ankney said the DNR has conducted herbicide treatment actions for invasive plants at Lower Pettibone Lake in Highland Township, Lakeville Lake in Addison Township, Orchard Lake, and Pontiac Lake in Waterford and White Lake townships.
“Lower Pettibone Lake, that’s one of the worst sites we have seen for (flowering rush),” he said. “It’s really aggressive there.”
“Right now, it’s not that bad,” Ankney said of the flowering rush problem in other Oakland County lakes. “But it gets very aggressive. We are seeing it come in stronger and stronger every year. There are pictures from areas a couple states to the south where it has filled in a complete wetland and created a monoculture.”
He said water hyacinth, water lettuce, and European frog-bit have been found in Oakland County and treatments for those plants is planned or has already been done.
To assist the DNR in locating and eradicating invasive plants, the Rapid Response program has listed eight species as potential threats and is asking the public to help report any sightings they find.
The priority aquatic invaders targeted by the joint effort include:
• Flowering rush (Butomus umbellatus): This invader was noted as being located in the Detroit River as early as 1918, but has spread across southeast Michigan — including Oakland County — in recent years.
Flowering rush is found in rivers, lakes, emergent wetlands and ditches in water up to 10 feet deep. It can be identified by its pale pink, rose, or white flowers of three petals and three petal-like sepals.
Cutting flowering rush under the water surface may reduce population density. In addition, digging out isolated plants may prevent spreading; however, bulbils on rhizomes must be removed.
Ankney said people shouldn’t pull flowering rush out by the root because it could actually help the plants spread.
“The only way to pull them would be to physically dig them up after drawing down the watertable,” Ankney said. “If you cut the tops off, which is where the flowers are and the seed heads will be, that could help. Burn or dispose of them so they won’t get back into the water or regular trash.”
Doug Pullman, owner of Aquest Corp. and vice president of the Michigan Aquatic Managers Association, said while flowering rush hasn’t been a large problem in Michigan, it has wreaked havoc in other states.
“What they saw in Minnesota is frightening,” Pullman said. “Even though we don’t see that here, you don’t want to take it off the list.”
• Starry stonewort (Nitellopsis obtusa): This exotic plant has been characterized as the most aggressive aquatic plant ever observed in Michigan and is able to outcompete all Michigan plant species and even other invasive species. Although it wasn’t positively identified in a Michigan inland lake until 2006, anecdotal evidence suggests that it has been present in Michigan lakes since the 1990s.
Starry stonewort is actually a species of algae. It’s generally rootless, although it can sometimes be loosely rooted. They feature little flowers that look like stars and tan-colored bulbils at the base of each cluster of branches. It grows in deeper waters, usually 10 to 12 feet deep or more, and can grow to a height of 7 feet or more.
Mechanical harvesting has been used to control starry stonewort but with little success. Fortunately, it has proven to be highly sensitive to common copper- and endothall-based algaecides.
Dick Pinagel, president of the Michigan Aquatic Managers Association and owner of Aqua-Weed Control, said he has been using a combination of copper-based herbicides to cut down starry stonewort and “give it a haircut.”
“It’s a tough plant,” Pinagel said. “It’s almost impossible to eradicate.”
• Parrot feather (Myriophyllum aquaticum): Native to South America, this invasive species forms dense mats of vegetation that can entirely cover the surface of water in shallow lakes, ponds, ditches, and backwaters in rivers. The tough stems make it difficult to boat, swim, fish, or water ski in infected areas, and it provides ideal habitat for mosquito larvae.
The invader can be identified by its bright green fir-tree-like emergent leaves and stems. Parrot feather’s underwater and above-water foliage hampers the effectiveness of herbicides, and the emergent leaves and stems are covered in a waxy cuticle that inhibits herbicide uptake.
Ankney said there haven’t been any confirmed sightings of parrot feather in Oakland county.
• Fanwort (Cabomba caroliniana): Although native to the southeastern U.S., fanwort is considered to be invasive in the northeast. It’s a rooted submersed plant with submersed and floating leaves of different shapes. The floating leaves are small, diamond-shaped, and infrequent.
Fanwort flowers are white to pink to purplish and are about a half-inch across. The flowers are on stalks which arise from the tips of the stems.
• Water lettuce (Pistia stratiotes): Experts differ on whether water lettuce is native to the U.S., as it’s been present in Florida since 1765. This floating plant commonly forms large infestations which prevent boating, fishing, and other uses of lakes and rivers.
Ankney said water lettuce has been verified in Pontiac Lake.
This invasive plant’s thick, soft leaves are formed in rosettes with no leaf stems. The flowers are inconspicuous, as they are nearly hidden in the center amongst the leaves.
Mechanical harvestors and chopping machines can be used to remove water lettuce from the water.
• Water hyacinth (Eichhornia crassipes): This invasive plant is considered to be one of the most troublesome aquatic weeds in the world, and is known to be persistent in the Detroit River and western Lake Erie.
Ankney said water hyacinth has been verified in Pontiac Lake.
The free-floating plant features distinctive air bladders that keep the leaves afloat and forms dense mats. Its leaves are thick, waxy, round and broad, while its showy flowers are lavender-blue in color with six petals. Upper petals feature a central, yellow blotch mark.
This invader can be thwarted by hand pulling small populations. In addition, several herbicides are effective.
• European frog-bit (Hydrocharis morsus-ranae): This species is a perennial, free-floating aquatic herb that forms large colonies creating dense mats with tangled roots.
The plant’s leaves, which resemble tiny water lilies, are kidney-shaped with long stems and have a dark purple color below. Its flowers are white and cup-shaped, and made up of three petals with yellow dots at the base.
European frog-bit occurs in shallow, slow-moving water on the edges of lakes, rivers, streams, swamps, marshes and ditches. No control measures have been reported for the species, but hand pulling or raking out colonies before fall is advised.
European frog-bit has been found almost exclusively in Southeast Michigan and along the Lake Erie shoreline, according to the DNR.
Pullman said the plant is common around the shores of Lake St. Clair, as well as in wet ditches around the lake.
“I’m not sure why it hasn’t spread beyond there,” Pullman said. “I don’t see it outside of that area. It’s another one that could be serious — in those ditches, it gets pretty darn thick.”
• Brazilian water-weed (Egeria densa): This submerged, rooted plant has three-petaled white flowers. It grows in still or slow-moving waters, including ponds, lakes, rivers and streams.
While reported but not confirmed in Michigan waters, Brazilian water-weed is a popular aquarium plant that reproduces by fragments that can be dispersed by waterfowl and boats — none of which bodes well for Michigan’s inland waterways.
The Rapid Response program, which is funded by a grant through the Environmental Protection Agency (EPA) and the Great Lakes Restoration Initiative, is scheduled to operate through September 2013. Ankney said the department hopes to generate as many leads as possible through the early detection process in order to help control aquatic invasive species in the future.
“There’s still time to carry on, and we hope to find long-term funding,” he said. “Because it’s a short-term project, the more leads we can generate the better.”
Those who discover these or other aquatic invasive species are asked to note their location and extent and contact Matt Ankney, early detection and rapid response coordinator for the DNR, at 517-641-4903, ext. 260. Reports can also be sent to Ankney via e-mail at firstname.lastname@example.org.
Reports can also be sent via e-mail to the Midwest Invasive Species Information Network at www.misin.msu.edu.