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Effects of 2, 4-D treatments to control Eurasian Watermilfoil on fish and zooplankton in northern Wisconsin lakes


April 2014 - December 2017


Eurasian watermilfoil Myriophyllum spicatum (EWM) is one of the most problematic aquatic invasive species in North America because it can outcompete native macrophytes (Madsen et al. 1991), negatively affect fish and wildlife, and interferes with recreational activities (Smith and Barko 1990). Application of herbicides is commonly used as a means to control or eradicate EWM (Sorsa et al. 1988; Parsons et al. 2001). Specifically, 2, 4-Dichlorophenoxyacetic acid (2, 4-D) based herbicides are widely used for controlling EWM in Wisconsin and other states, but little is known regarding the effects of these herbicide treatments on fish and zooplankton communities outside of a laboratory setting. One previous study indicated that application of 2, 4-D herbicides did not affect fish diversity or biomass in two Minnesota lakes (Kovalenko et al. 2010), but application of these herbicides remains an important concern for the Wisconsin Department of Natural Resources (WDNR), which issues the permits required for herbicide application in Wisconsin lakes. Consequently, the objectives of our study are to determine if: 1) 2, 4-D herbicide treatments used to control EWM affect the abundance, diversity, and size structure of fish at different life history stages; 2) herbicide treatments affect feeding, survival, growth, and reproductive investment of selected fish species, and 2) if herbicide treatments affect diversity, abundance, and size of zooplankton. Our working hypotheses are that 2, 4-D herbicide treatments will not reduce fish diversity, but will reduce abundance and survival which will eventually influence the size structure of fish populations in treated lakes through reduced recruitment. Furthermore, we hypothesize that herbicide treatments will not affect gonadal investment and fecundity, but will reduce survival, foraging success, and growth of larval fish. Lastly, we hypothesize that herbicide treatments will not affect zooplankton diversity, but will result in increased abundance and size structure of zooplankton because of reductions in larval fish predation.

Research Products and Activities


  • Rydell, N.J. 2018. Effects of 2, 4-D Herbicide treatments used to control Eurasian Watermilfoil on fish and
    zooplankton in northern Wisconsin lakes. M.S. Thesis. University of Wisconsin-Stevens Point. 119 p.

Current Staff

Federal Staff: 95

Masters Students: 240

Phd Students: 143

Post Docs: 52

University Staff: 245

5 Year Summary

Students graduated: 702

Scientific Publications: 1948

Presentations: 4246



Funding Agencies

  • Wisconsin Department of Natural Resources


Cooperative Research Units Program Headquarters Cooperators

  1. U.S. Geological Survey