What type of pesticide remains effective for a longer period and does not wash away easily?

The correct answer is residual pesticide. Residual pesticides are designed to remain active on surfaces long after they've been applied, which makes them effective for an extended period. This characteristic is crucial in pest management, particularly for controlling mosquitoes, as it allows for prolonged protection against reinfestation.

These types of pesticides adhere to surfaces and continue to work by killing or repelling pests that come into contact with them over time. This enduring effectiveness can be particularly advantageous in areas prone to frequent mosquito activity, as it reduces the need for repeated applications.

In contrast, contact pesticides act quickly upon application but do not provide long-lasting effects, as they are typically designed to kill pests on contact without any residual activity. Systemic pesticides are absorbed by plants and affect pests that consume plant materials, but they don't have the same surface persistence. Non-residual pesticides, as the name suggests, offer minimal or no remaining activity once applied, making them less effective for prolonged control.