Restricted use insecticides are defined as those that:

Restricted use insecticides are specifically designed to be utilized only by individuals who are certified or licensed to handle them. This restriction is in place due to the potential risks associated with these products, which may include higher toxicity levels to humans, pets, and the environment, as well as the need for specialized knowledge regarding their application and safety measures.

The requirement for certification ensures that the individuals applying these insecticides have the necessary training to handle them responsibly, thereby minimizing the risk of misuse or accidental exposure. This distinction helps to ensure that these more hazardous substances are applied safely and effectively, limiting their use to professionals who are knowledgeable about the regulation and safety protocols associated with these chemicals.

Other options do not correctly describe the nature of restricted use insecticides. For instance, unrestricted accessibility by anyone would contradict the purpose of regulating these substances, while claims regarding efficacy and shelf life do not pertain to their categorization as restricted use.