What is the primary concern when applying pesticides near water sources?

The primary concern when applying pesticides near water sources is the potential for contamination and harm to aquatic life. Pesticides can easily be carried into water bodies through runoff, leaching, or even during application, especially if proper precautions are not taken. Aquatic ecosystems are highly sensitive to the introduction of chemicals, which can lead to toxic effects on fish, invertebrates, and other organisms living in or around these environments. Protecting water sources is crucial not only for aquatic life but also for maintaining overall environmental health and preventing issues such as bioaccumulation and the potential harm to humans and wildlife that depend on these water sources.

Other considerations, such as pest behavior, evaporation rates, and application costs, while relevant in specific contexts of pest control, do not pose the same immediate and severe ecological risks as the direct impact pesticides can have on freshwater systems and their inhabitants.