What best describes the main effect of applying residual pesticides?

Applying residual pesticides is intended to provide a long-term effectiveness against pests. These pesticides are formulated to adhere to surfaces and remain active for an extended period, which means they can continue to control pest populations even after the initial application.

The long-lasting properties of residual pesticides contribute to their effectiveness by allowing for prolonged pest management in treated areas. This is particularly beneficial in situations where pests might otherwise return quickly after a treatment, ensuring that both immediate and future infestations are minimized.

While some pesticides may achieve immediate extermination, that is not the defining characteristic of residual pesticides, as their primary function is to maintain a persistent barrier against pest activity over time. The other options — no impact on pest populations and increased growth of non-target plants — do not accurately reflect the purpose or function of residual pesticides. In contrast, their formulation is specifically developed to impact targeted pest species effectively while minimizing unintended consequences.