Which of the following is a significant risk of improper application of aquatic herbicides?

The significant risk of improper application of aquatic herbicides primarily revolves around the potential for plant resistance to those herbicides. When herbicides are not applied correctly—whether through incorrect dosages, timing, or environmental conditions—certain aquatic plants can be exposed to sub-lethal levels of the chemical. This repeated exposure can lead to the development of resistance, which is a significant concern because it limits the effectiveness of these herbicides in the future. Once plants develop resistance, controlling them becomes increasingly difficult, prompting the need for more potent chemicals or alternative management strategies, which can further disrupt aquatic ecosystems.

In contrast, increased water transparency, improved water quality, and higher fish populations are generally associated with effective aquatic herbicide application that properly targets nuisance species. However, improper application does not lead to positive outcomes in these areas, which reinforces why plant resistance is a major risk factor that must be managed carefully in aquatic herbicide use.