Which type of pesticide requires more frequent reapplication due to its mode of action?

The type of pesticide that requires more frequent reapplication due to its mode of action is the contact pesticide. Contact pesticides work by directly affecting the pests upon contact. They do not penetrate into the plant system or persist in the environment very long, leading to a shorter residual effectiveness. As a result, once the pesticide has been applied, it can quickly degrade or be washed away, necessitating more frequent applications to maintain pest control.

In contrast, systemic pesticides are absorbed by the plant and can offer residual effects over a longer period, as they act from within the plant system. Selective pesticides target specific pests or groups of pests while having minimal impact on non-target organisms, allowing for effective control over time. Non-selective pesticides kill a broad range of pests and may not require as frequent reapplication as contact pesticides because their active ingredients tend to persist in the environment longer. Thus, the nature of contact pesticides leads to the need for more regular reapplication to effectively control pest populations.