08-15-2007
New Aquatic Invasive Weed Found in Northeast Wisconsin

MADISON--An invasive weed that has caused other states to spend much time and money to manage it, has been found in an artificial pond in Marinette County in northeast Wisconsin.

State and federal officials have confirmed that the plant is Hydrilla or Hydrilla verticillata, an aquatic plant that grows into dense mats near the water's surface. Hydrilla is native to Asia and is classified as a federal noxious weed. It is illegal to transport hydrilla across state lines unless a permit has been granted by federal authorities.

The fast-growing plant was found in a large artificial pond on private property. The homeowners constructed the one and one-half acre pond in 2004.

"The good news is this pond is not connected to any natural water body so we believe the hydrilla is contained on this site," explained Bob Dahl, plant regulatory section chief with the Wisconsin Department of Agriculture, Trade and Consumer Protection. "The bad news is that another invasive species has reached our state. We will check surrounding ponds and other bodies of water to determine if hydrilla is located elsewhere."

Pond owners and people who live along lakes and rivers are encouraged to check plants in those waterbodies to make sure they are not hydrilla. Photos and more information are available on the Department of Natural Resources web site.

"Hydrilla stems are slender, branched and up to 25 feet long with saw-toothed leaf margins and sharp teeth on the leaf's midrib. Hydrilla also produce tiny white flowers and have potato-like tubers attached to the roots in the mud," explained Tim Asplund, DNR water resources management specialist.

If you suspect that you have hydrilla, contact your local DNR service center. Check the government pages of your phone book or the DNR web site.

Based on information from the homeowners, it appears the hydrilla has been in the pond since 2005.

"The hydrilla was originally mistaken for elodea, a native water plant," Asplund said. "It wasn't until recently that the plant was correctly identified and confirmed as hydrilla by the USDA Animal and Plant Health Inspection Service laboratory in Beltsville, Maryland."

A native elodea (ee-low-DEE-ah) or American waterweed looks very similar but only has three grouped leaves or whorls on the stem and hydrilla always has more than three whorled leaves Asplund explained.

The state agriculture department and their partners in the investigation, the DNR and the United States Department of Agriculture, haven't yet determined the source of the hydrilla but officials say the owners of the pond have been very cooperative as the work continues.

"We need to get this under control and determine how this weed got into Wisconsin," Dahl said. "State and federal staff have visited the pond and we're working to determine the most safe, efficient means of eradication because we don't need another invasive plant in Wisconsin like Eurasion milfoil," Dahl said.

Hydrilla has been found in Indiana, Florida, Texas and Washington. In Florida, millions of dollars are spent each year to control this weed that chokes out native vegetation, tangles boat motors and interferes with other water recreation.
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