What defines an Insect Growth Regulator (IGR)?

An Insect Growth Regulator (IGR) is defined as a chemical that disrupts insect development by interfering with hormones. IGRs work by mimicking or blocking the insect hormones that regulate growth and development, which may lead to abnormalities in the insect life cycle, such as preventing molting or reproduction. This disruption effectively controls insect populations over time without directly killing them; instead, it hampers their ability to mature and reproduce.

The other options do not accurately describe the unique function of IGRs. For example, a type of pesticide that kills insects on contact refers more to conventional insecticides that are designed to immediately eliminate pests rather than regulating their growth. Also, natural substances used to repel insects do not fit the criteria for IGRs, as they are not intended to interfere with development processes. Finally, a mixture of various insecticides might be effective for pest control but does not specifically address the hormonal interference that characterizes IGRs.