What is the difference between IGRs (Insect Growth Regulators) and IDIs (Insect Development Inhibitors)?
IGRs and IDIs are used in monthly flea prevention products to eliminate the immature form of the flea. The difference in the two is subtle: IGRs – This group includes methoprene (Precor), fenoxycarb, and pyriproxyfen (Nylar). An IGR mimics the juvenile growth hormone of fleas. The juvenile growth hormone is what keeps the fleas from developing into more mature forms. Normally, as the level of juvenile growth hormone decreases, the larva, the worm-like offspring of an insect form, matures. Since the IGR keeps the level of the hormone from decreasing, the juvenile never develops into an adult; it fails to molt and then dies. IDIs – Insect development inhibitors include lufenuron and diflubenzuron. IDIs inhibit the synthesis of a substance called chitin (the outside, protective “shell” of the insect). Chitin is necessary for the formation of the hard outside skin (cuticle) of the flea. No chitin, no adult flea. IGRs and IDIs do not kill adult fleas, so to be most effective they should be
