10-04-2007
Battle Against Hydrilla Continues

Carroll Schaal, (608) 261-6423, DNR lake protection

MADISON-Since a fast-growing invasive plant was first identified in August in a private Marinette County pond, the pond has been chemically treated and state and county officials have been surveying other area waters to assure the plant isn't present in nearby water bodies. They also are working with the pond owners and federal officials to develop a permanent response plan.

"Our goal is to eradicate this plant from the pond so there is no on-going risk to Wisconsin waters," said Bob Dahl, Wisconsin Department of Agriculture, Trade and Consumer Protection plant regulatory section chief.

"The pond owners have been very cooperative during the investigation and initial response, and we are working closely with them and partnering agencies to develop an effective, comprehensive plan to eliminate the hydrilla," Dahl said.

Hydrilla or Hydrilla verticillata, an aquatic plant that grows into dense mats near the water's surface, was confirmed by federal officials earlier this summer, marking Wisconsin's first documented occurrence of the plant, which other states have spent millions trying to control. Hydrilla is native to Asia and is classified as a federal noxious weed, making it illegal to transport across state lines without a federal permit.

The state agriculture department has been working with the Department of Natural Resources, the United States Department of Agriculture and Marinette County to trace the plant's origins and determine a response to keep it from spreading.

Already, an aquatic herbicide was applied to the pond by a professional pesticide applicator to prevent migrating waterfowl from moving bits and pieces of the plant to other locations where it could take root.

"The pesticide application appears to be working as the green vegetation is dying," said Greg Sevener, a DNR aquatic plant manager.

Surveying surrounding bodies of water and identifying the original source of this fast growing aquatic weed are also critical parts of the initial response, he says. "This pond isn't connected to any natural water body but there is the chance that hydrilla can be spread by waterfowl."

DNR and Marinette County staff have checked over a dozen natural and artificial ponds and rivers for the presence of hydrilla. The work will continue through the month before falling temperatures will cause hydrilla, if it's present anywhere else, to die back and make it difficult to spot in the water.

In coming weeks, once the area survey is complete, the agency partners and the pond owners will discuss various control options and develop a more permanent solution to address the plant roots that remain in the pond sediment. Finding the original source of the hydrilla also continues as staff review plant nursery shipping records and invoices from the past few years.

"The tracing of plant material can be a bit complicated as we have to track product shipments. The search depends on the completeness and quality of a company's records and if the plant material originated within Wisconsin or came from other states or countries," Dahl said. "If we find the original source of the hydrilla, the next pressing question is--did other plants come into Wisconsin and where did they go?"

The one and one-half acre pond located in northeast Wisconsin was constructed in 2004. The following year, the plant was noticed but mistakenly identified for a similar looking native water plant called elodea (ee-lo-DEE-ah).

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