What does a residual pesticide do after application?

A residual pesticide is designed to remain effective for an extended period after application. This characteristic allows it to continue controlling pest populations over time, rather than only providing immediate, short-term effectiveness. The formulation of these pesticides is intended to adhere to surfaces and gradually release active ingredients, which can help in managing pest populations effectively by providing ongoing protection against infestations.

In contrast, some options suggest characteristics that do not apply to residual pesticides. For instance, becoming ineffective immediately would undermine the purpose of using a pesticide meant for long-term control. Rapid evaporation would also limit its effectiveness, as the active ingredients would not persist in the environment to affect pests. Lastly, stating that a residual pesticide has no impact on pests contradicts its fundamental function, which is to control or eliminate unwanted pests over a sustained period. Thus, the correct understanding of residual pesticides emphasizes their longevity and effectiveness beyond the initial application.