Insect growth regulator

Definition

A chemical agent that disrupts insect development and reproduction by interfering with hormonal or cuticular processes rather than causing acute toxicity. IGRs act through three principal modes: juvenile hormone analogs (JHAs) that prolong larval stages and prevent metamorphosis; chitin synthesis inhibitors (CSIs) that block formation of new cuticle during molting; and ecdysone receptor agonists that trigger premature or incomplete molts. Because they target pathways specific to arthropods, IGRs generally exhibit low vertebrate toxicity and are classified as reduced-risk pesticides.

Etymology

From 'insect' + 'growth' + 'regulator', coined in the 1970s when juvenile hormone analogs were first developed commercially; the term was preferred over the more accurate 'insect growth disruptor' for marketing purposes.

Example

Diflubenzuron, a chitin synthesis inhibitor, is applied to mosquito breeding water to prevent larvae from forming functional exoskeletons at their next molt, causing death without affecting non-arthropod aquatic organisms.

Synonyms

• IGR
• insect growth disruptor

Related Terms

• Juvenile hormone
• Ecdysone
• Chitin
• molting
• Metamorphosis
• Pesticide
• Integrated Pest Management
• endocrine disruptor

Usage Notes

The term is sometimes criticized as a misnomer because these chemicals disrupt rather than 'regulate' growth. IGRs are slow-acting compared to conventional neurotoxic insecticides and are most effective against immature stages; they do not kill eggs and have limited efficacy against adults. Resistance management requires rotation with other modes of action. Not all growth-affecting compounds are classified as IGRs—antifeedants and molting accelerators fall outside the standard definition despite affecting development.