Which indicator can signal the need for herbicide treatment in a water body?

The need for herbicide treatment in a water body is primarily indicated by excessive growth of target plants. This phenomenon often signifies that the aquatic ecosystem is being overwhelmed by certain plant species, which can lead to detrimental effects on water quality, biodiversity, and fish habitats. When target plants, such as invasive or unwanted aquatic vegetation, proliferate excessively, they can restrict light penetration, deplete dissolved oxygen levels, and disrupt the normal ecological balance.

Recognizing the signs of excessive plant growth allows for timely intervention with herbicide treatments to manage these populations effectively. It is crucial to address these issues before they escalate, as unchecked growth can lead to more severe environmental impacts that are harder to remediate. In contrast, stable water quality, increased fish activity, and declining soil health do not specifically indicate the immediate need for aquatic herbicide treatments, as they encompass broader or unrelated ecological concerns that may not directly connect to plant management.