Effects of 2, 4-D Herbicide Treatments Used to Control Eurasian Watermilfoil on Fish and Zooplankton

Eurasian watermilfoil (EWM) Myriophyllum spicatum is one of the most problematic invasive macrophytes in the United States. Eurasian watermilfoil spreads easily and often displaces native aquatic plants, causing economic and ecological damage.  The aquatic herbicide 2, 4-Dichlorophenoxyacetic acid (2, 4-D) is widely used to control EWM. However, little is known regarding the effects of 2, 4-D on zooplankton and fishes, especially in natural systems. Our objectives are to determine if 2, 4-D treatments affect: 1) the abundance, diversity, and size structure of fishes at different life history stages; 2) feeding, survival, and growth of larval fish, and 3) diversity, abundance, and size of zooplankton. This study will be conducted on six lakes in northern Wisconsin over a three year period, including a pre-treatment, treatment and post-treatment year. During the treatment year, three lakes will serve as reference systems, while three lakes will receive a whole lake 2, 4-D herbicide treatment. Information collected during this study will aid managers in determining the use of 2, 4-D treatments for whole lake manipulations.