http://www.madison.com/wsj/home/opinion/index.php?ntid=48750&ntpid=0

July 30, 2005

Wisconsin State Journal

Opinion

Lake weed problem defies simple solution

Weeds have covered parts of many Madison lakes this summer, including Monona Bay.

It's understandable that Dane County residents this summer are wishing for a magic potion to rid the Yahara lakes of invasive weeds forever. But there is no evidence that the chemical weed killer called fluridone is that potion.

That's not to say fluridone deserves to be disregarded. It has some intriguing potential as an element of a strategy to control non-native weeds like Eurasian watermilfoil, which have invaded the lakes. But it is to say that the campaign to use fluridone as whole-lake weed eradication treatment should slow down.

Fluridone has surged into the local vocabulary this summer on a groundswell created by lakeshore homeowners and boaters frustrated with the growing weed problem in Dane County's lakes.

Prompted by success stories trumpeted by a company that sells fluridone treatments, several Dane County residents are promoting the chemical for use on local lakes.

Lakeshore property owners already may pay for chemical spot treatments for weeds, under state Department of Natural Resources' supervision. But the goal of the fluridone boosters is to use the chemical in a whole-lake weed treatment aimed at eradicating watermilfoil. A petition is circulating to request the DNR to approve fluridone's use.

But as DNR researchers are well aware, fluridone is hardly an unqualified success. It has been employed on several lakes nationwide with mixed results.

The chief problems include the temporary nature of fluridone's effectiveness. Watermilfoil tends to return in two to five years, sometimes thicker than ever.

Furthermore, in eutrophic lakes like Monona and Mendota - which are so rich in nutrients that they produce excessive plant growth - there is some evidence that fluridone use eventually makes water murkier and kills off native plants. The elimination of native plants, in turn, raises questions about whether the chemical might disrupt a lake's food chain, threatening fish populations.

The potential threat to fish ought to raise caution flags for fluridone's use on Madison lakes, which now yield excellent fishing.

To be sure, fluridone has yielded some success stories. At Houghton Lake in Michigan, state DNR officials were skeptical of a 2002 fluridone whole-lake treatment. But three years later residents report satisfaction with the results.

The Houghton Lake treatment came at a steep price, however. Lake residents and businesses within two miles of the lake were assessed $1.4 million to pay for it. Moreover, follow-up spot treatments are needed to keep watermilfoil in check.

In the state of Washington researchers found that the keys to success for fluridone include residents' willingness to finance and conduct follow-up monitoring and treatments. It's not a one-shot-and- done solution.

In light of the experience elsewhere, it's too early to judge whether a fluridone whole-lake treatment on the Yahara lakes would be worth the cost. The DNR and Dane County lake users should continue to monitor fluridone's use throughout the country and the research conducted on it. Fluridone may have a place in Dane County's lakes management plan. But before we use the chemical we should have a clearer idea of its impact.

Meantime, Dane County officials and residents should continue to focus on long-term control of the proven contributors to the lake weed problem: nutrients such as phosphorus fertilizer and the runoff that carries those nutrients into the lakes.

The weed problem in Madison area lakes did not grow swiftly from a single cause. It is unlikely to be solved swiftly by a single chemical weed killer.