Chapter 11

Insect Pest Management for Organic Crops

Insect Growth Regulators

Insect growth regulators (IGRs) use a different and more selective mode of action; they disrupt the growth process of insects, preventing them from the reaching reproductive stage. IGRs have a complex mode of action that precludes insects from rapidly developing resistance. IGRs can work in one of several ways: 1) they can mimic juvenile hormones, so that insects never enter the reproductive stage of development; 2) they can interfere with the production of chitin, which makes up the shell of most insects; or 3) they can interfere with the molting process. For most IGRs, there are minimal re-entry restrictions. IGRs typically take several days to have an effect on pest populations.

Azadirachtin

Azadirachtin is one of the most widely used botanical insect growth regulators. Because of its structural resemblance to the natural insect molting hormone ecdysone, azadirachtin interrupts molting, metamorphosis, and development of the female reproductive system. Immature insects exposed to azadirachtin (mainly by ingestion) may molt prematurely or die before they can complete a properly timed molt.

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