What aquatic plant is commonly managed with herbicides in Indiana?

C. Eurasian watermilfoil is the correct answer because this invasive aquatic plant is a significant concern in Indiana's water bodies. It tends to proliferate rapidly, outcompeting native vegetation and disrupting local ecosystems. The management of Eurasian watermilfoil often necessitates the use of herbicides designed specifically to target this species while minimizing harm to desirable native plants and the overall aquatic environment.

While water lilies and duckweed can be managed with herbicides, they are often a natural part of aquatic ecosystems and may not require the same level of intervention as Eurasian watermilfoil, which poses specific ecological threats. Algae, while also a target for management, are typically controlled through different methodologies such as nutrient management, as herbicides are not as effective in managing algal blooms compared to other strategies. Therefore, Eurasian watermilfoil stands out as a primary candidate for herbicide application in Indiana's aquatic management efforts.