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Insect growth regulators (IGRs) are insecticides that mimic hormones in young insects. They disrupt how insects grow and reproduce. IGRs can control many types of insects including fleas, cockroaches, and mosquitos. Although they are rarely fatal for adult insects, they can prevent reproduction, egg-hatch, and molting from one stage to the next. Many IGR products are mixed with other insecticides that kill adult insects. IGRs are generally low in toxicity to humans.

How do IGRs work?

adult flea Adults usually survive IGR treatments and continue to be a nuisance until they die naturally. However, the eggs they produce may not survive. Sometimes adults’ reproductive organs are affected and the adult becomes sterile.
flea egg Eggs treated with IGRs may never hatch. If the eggs do hatch, the young insect may not survive.
flea larva The larva, or worm-like stage, may not be able to develop correctly into an adult after exposure to IGRs. Some larvae may stay in this juvenile stage until they die.
flea pupa A case like a moth’s cocoon usually protects the pupa. Treatment with an IGR may prevent the pupa from becoming an adult and reproducing.

IGRs affect certain hormones in insects, hormones that humans don’t have. They don’t kill insects immediately, but they can stop a pest population from reproducing until all of the pests have died.

Keep these tips in mind:

Additional Resources:

Information about specific IGR chemicals:

If you have questions about this, or any pesticide-related topic, please call NPIC at 800-858-7378 (8:00am - 12:00pm PST), or email us at npic@ace.orst.edu.

Last updated January 28, 2024