What is the primary purpose of encapsulated pesticides?

Encapsulated pesticides are specifically designed to release their active ingredients slowly over time, which allows for prolonged effectiveness against target pests. This slow-release mechanism enhances the duration of action, reducing the frequency of applications needed and providing a more sustained level of pest control. Additionally, the encapsulation helps to protect the active ingredient from environmental factors that could degrade it, making it more stable and effective over an extended period.

The other options refer to methods of pesticide action that do not align with the properties of encapsulated products. Immediate release of the active ingredient would imply different formulations that act quickly and are designed for rapid pest knockdown. Similarly, increasing evaporation speed might suggest volatility in the formulation contrary to the controlled release characteristic of encapsulated pesticides. Lastly, while immediate contact kill is important in some pesticides for quick pest management, encapsulation focuses on sustained efficacy rather than instant results. Therefore, the correct choice highlights the encapsulated pesticide's function of prolonged effectiveness.