Insecticides Acting as Juvenile Hormone Mimics

Juvenile hormone (JH) is a necessary chemical at certain times in insect development, but becomes toxic when present during metamorphosis, i.e., when normal JH titers are low. JH mimics (methoprene, hydroprene, fenoxycarb, and pyriproxyfen) act similar to JH and exhibit the highest toxicity when applied at the onset of metamorphosis. 

Early reports suggested that methoprene exerted its toxic effect not as a JH mimic but as an inhibitor of JH degradation, resulting in the accumulation of endogenous JH (Slade and Wilkinson, 1973). More recent studies involving insect tissue culture or cell culture have eliminated this hypothesis. 

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