Date of Graduation
Master of Science in Biology
Eurasian water-milfoil, Myriophyllum spicatum, milfoil weevil, Euhrychiopsis lecontei, biological control, bluegill, Lepomis macrochirus, diet
Eurasian water-milfoil (Myriophyllum spicatum L., henceforth “EWM”) is the most heavily managed nuisance submersed aquatic plant in the United States. EWM’s rapid spring growth and formation of dense surface mats inhibits native macrophyte communities, serves as poor-quality habitat for fish and macroinvertebrates, impacts recreation, and can clog water supply infrastructure. The milfoil weevil (Euhrychiopsis lecontei Dietz) has been associated with EWM declines in several states, though natural weevil densities are generally too small to effect control. Augmentative biocontrol has had varied success and fish predation may account for high weevil mortality. Weevils were augmented in 4 northern Wisconsin lakes in summer 2013. In summer 2014, I collected invertebrates associated with EWM plus 442 bluegill (Lepomis macrochirus Rafinesque) diet samples from the 4 study lakes. Overall, chironomids and oligochaetes were the dominant invertebrates associated with plants, while chironomids and Daphnia spp. constituted up to 27.2% and 24.0% of the fish diets, respectively. Milfoil weevils were found in 2.9% of diet samples examined. Weevil larvae were preyed upon more frequently than adults (94.2% of weevils consumed) and sometimes occurred in high numbers within single diet samples. Since the larval stage contributes the most to EWM damage, selective predation on this stage may limit its use as a control agent.
© Kristopher Andrew Maxson
Maxson, Kristopher Andrew, "Trophic Interactions And The Efficacy Of Milfoil Weevils For Biocontrol Of Eurasian Watermilfoil In Wisconsin Lakes" (2016). MSU Graduate Theses. 13.