What defines a residual pesticide?

A residual pesticide is defined by its ability to control pests for an extended period after application. This characteristic means that these pesticides remain active in the environment for a certain duration, allowing them to continue affecting pest populations long after the initial application. This prolonged effectiveness is beneficial as it reduces the frequency of applications needed, ensuring that pests are kept in check over time.

In contrast, pesticides that lose effectiveness quickly do not provide extended pest control and require more frequent reapplication, making them less efficient in many situations. Pesticides that are absorbed by the soil immediately may not have a lasting effect on pests above ground and would not qualify as residual if they cannot persist in the environment. Lastly, a pesticide that is only effective when applied in large amounts may not inherently have residual qualities; its effectiveness could be tied to dosage rather than its ability to persist over time. Thus, the defining feature of a residual pesticide is its sustained efficacy against pests.