Insecticides with growth regulating properties (IGR) may adversely affect insects by regulating or inhibiting specific biochemical pathways or processes essential for insect growth and development. Some insects exposed to such compounds may die due to abnormal regulation of hormone-mediated cell or organ development. Other insects may die either from a prolonged exposure at the developmental stage to other mortality factors (susceptibility to natural enemies, environmental conditions etc) or from an abnormal termination of a developmental stage itself. Insect growth regulators may come from a blend of synthetic chemicals or from other natural sources, such as plants. The chemical composition of hormones indigenous to insects is now being studied and used as a basis for developing analogues or mimics against insects. The similarities, however, in certain aspects of biochemistry among vertebrates and invertebrates may result in the limited development of IGRs.

1. INSECT GROWTH
REGULATORS
Chairman: Dr. Vivekanand
Gradial Seminar
BPC789
Presented by: Himani
Id: 53942
Ph.D. Agricultural Chemicals

2. Contents
• Introduction
• Growth regulation of insects
• Classification of IGRs
• Synthetic IGRs
• Juvenile hormone
• Anti-juvenile hormone
• Chitin synthesis inhibitors
• Moulting hormone analogues
• Natural IGRs
• Advantage
• Disadvantage
• References

3. INTRODUCTION
IGRs: compounds that interfere with the growth and development of
insects.
III generation pesticide
Insect can not reach adulthood and can’t reproduce.
IGR is a short term of birth control in pests.

4. Hormonal control of insect development
Prothoracic
gland
BH
 JH, ecdysone stimulates
moulting producing
another larval stage, JH
suppress metamorphosis
JH, a pupa forms at the next ecdysone induced
molt. The adult insect emerges from the pupa

5. IGRs
Synthetic
Chitin
synthesis
inhibitors
Juvenile
hormone
analogues
Anti juvenile
hormone
agents
Moulting
hormone
analogues
Natural
Classification Of IGRs

6. Synthetic Insect Growth Regulators
Chitin Synthesis Inhibitors (CSIs)
N-acetyl-D-glucosamine
β-(1→4)-linkages

7. Chitin Synthesis Inhibitors (CSIs)

8. CSIs
Biosynthetic Pathway of Chitin Synthesis

9. Market available products

10. Juvenile hormone analogues
• Juvenile hormones (JHs) : acyclic sesquiterpenoids that regulate
many aspects of insect physiology.
• The first discovery of a JH was by Vincent Wigglesworth.
• JHs regulate development, reproduction, diapause in insects
• The main role of JH in immature insects is to ensure as well as inhibit
the development of adult characteristics, causing the insect to remain
as nymph or larva.
• During the last larval or nymphal instar, the corpora allatum becomes
atrophied and stops producing juvenile hormone

11. Farnesyl
pyrophosphate (FPP)
Phosphatase or
pyrophosphatase
Farnesol
Farnesol dehydrogenase, NAD+
Farnesal
Farnesal dehydrogenase, NAD+
Farnesoic
acid
Methyl transferase
S-adenosyl-methionine
Epoxidase, O2,
NADPH + H+
Epoxidase, O2,
NADPH + H+
Juvenile
hormone
III acid
(JHA)
Methyl transferase
S-adenosyl-methionine
Methyl farnesoate
Juvenile hormone III

12. JH 0, I, and II : Lepidoptera (butterflies and moths)
Diptera, or flies.

13. Methoprene and others are broad-
spectrum synthetic JH
mimic/analogues, which acts as
an IGR (insecticide). It prevents larval
metamorphosis to viable adults and thus
acts as a larvicide and interferes with the
insect life cycle, preventing the insect
from reaching maturity or reproducing.

14. Market available JHAs products

15. Market available JHAs products

16. Anti-juvenile hormone agents (Precocenes)
• They act by destroying corpora allata (CA) and preventing JH synthesis.
• When treated on immature stages of insect, they skip one or two larval instars and turn into
tiny precocious adults.
• They can neither mate, nor oviposit and die soon.
• Fluoromevalonate (FMev) exhibited anti-JH activity in Lepidoptera
• Piperonyl Butoxide: mixed function oxidase (MFO) inhibitor, inhibits oxidative
degradation of xenobiotics and used as a synergist with pyrethrin / pesticides and
inhibits JH biosynthesis in terminal steps
• Precocenes exert cytotoxic action on the insect CA by an oxidative bioactivation and
prevent JH production.
• Physiological and behavioral changes induced by precocenes : precocious
metamorphosis, sterilization of adults,suppressed ovarian development, induction of
diapause and inhibition of sex pheromone production.

17. Abnormalities resulting
from precocene I
treatment, in forth instars
and adult E. integriceps
treated in third instar. (A)
Normal fourth instar, (B)
and (C) abnormal fourth
instar, (D) normal adult,
(E) abnormal adult.
Amiri et al., 2010
Precocene I

18. Moulting hormone analogues (MHAs)
• MHAs blocks the biosynthesis of moulting hormone
and disrupts moulting processes.
• Defective cuticle
• Development process accelerates bypassing several
normal events resulting in integument lacking scales
or wax layer.
• Also affects egg production and spermatogenesis in
adults.

19. Ecdysone (molting agonist/initiator)
• Ecdysone is a steroid hormone secreted by prothoracic gland that, in its active
form, stimulates metamorphosis and regulates molting in insects.
• 20-Hydroxyecdysone (ecdysterone or 20E) is a naturally occurring
ecdysteroid hormone which controls the ecdysis (moulting) and
metamorphosis of arthropods.
ecdysone 20 monooxygenase

20. Market available MHAs Products

21. • Leaf and seed extract of Azadirachta indica
• Mimics insect hormones called ecdysones
that regulate pupation of insects
• Application of azadirachtin interrupts the
development and pupation of insects, which
eventually kills them.
Natural Insect Growth Regulators
Commonly used Natural IGRs are: Azadirachtin, Plumbagin etc
Azadirachtin
C35H44O16

22. • Root extract of the plant Plumbago
• The mode of action of plumbagin is
being a chitin synthesis inhibitor
• It affects the mechanical properties of
the insect cuticle and produces
abnormalities in the skin and resists
moulting.
• Inhibition of moulting results in
increase of the internal body pressure
in the larvae.
Plumbagin

23. • Chloroform extract of leaves of
Chrysanthemum coronarium
• The mode of action of Polyacetylenic
sulfoxide is being an anti-juvenile
hormone
• Polyacetylene is highly photolabile and
appears to possess a cytotoxic mode of
action similar to the precocenes.
Polyacetylenic sulfoxide

24. Active Component Source Successful Examples
List of some other Natural IGRs

25. Advantages of IGRs Disadvantages of IGRs
• Effective in minute quantities, so
are economical.
• Target specific, safe to natural
enemies.
• Bio-degradable, non-persistant,
non-polluting
• Non-toxic to human, ani.mals
• Well fitted into IPM programme.
Comes under biorationals
• Less chances to resistance.
• Kills only certain stages of pest.
• Slow mode of action (IGRs work
by interfering with an insect's
molting process. Death 3-10
days)
• Not easily available.
• High cost
• Unstable in the environment

26. References
1. Gad, M., Aref, S., Abdelhamid, A., Elwassimy, M., & Abdel-
Raheem, S. (2021). Biologically active organic compounds as
insect growth regulators (IGRs): introduction, mode of action, and
some synthetic methods. Current Chemistry Letters, 10(4), 393-
412.
2. Tunaz, H., & Uygun, N. (2004). Insect growth regulators for insect
pest control. Turkish Journal of Agriculture and Forestry, 28(6),
377-387.
3. http://eagri.org/eagri50/ENTO232/lec23.pdf