Pesticides are designed to kill or repel pests, but the chemicals can linger on surfaces long after they've been applied. The length of time a pesticide remains active depends on many factors, including the type of pesticide, the amount of sunlight and heat exposure, and rainfall.
In general, most pesticides will remain active for 1-2 weeks after application. However, there are some exceptions. For example, herbicides that contain glyphosphate can last for several months in ideal conditions. And insecticides with pyrethrin can remain potent for up to a year if they're used indoors.
To be safe, always follow the instructions on the pesticide label and contact your local extension office for more information about specific products.