What is a potential result of pesticide over-application?

Over-application of pesticides can lead to water pollution due to runoff. When pesticides are applied in excess, they can wash off the treated areas during rainfall or irrigation, entering nearby water bodies. This contamination can harm aquatic ecosystems, disrupt local wildlife, and potentially affect drinking water sources.

While enhanced crop yield, increased pest resistance, and improved soil structure are important considerations in pest management practices, they do not accurately represent the negative consequences of over-application. In fact, overuse can lead to increased pest resistance, as pests that survive chemical applications may develop resistance to those chemicals over time, but this option does not directly relate to the immediate environmental impact like water pollution does. Thus, the most prominent and direct environmental consequence is indeed water pollution due to runoff, making this the correct choice.