Insecticide Mode of Action
Training slide deck
IRAC MoA Workgroup
Version 1.0, April 2019
1 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright What is an Insecticide’s ‘Mode of Action’?
The Mode of action defines the process of how an insecticide works on an insect or mite at a molecular level
Why is it good to know the Mode of Action of an Insecticide?
Knowing the Mode of action of an insecticide is key to managing resistance
The Insecticide Resistance Action Committee (IRAC) is a coordinated industry response to resistance management
2 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright ADME is an important factor in an insecticide’s bioavailability n Absorption q Through the cuticle q Orally through consumption q Inhaled through spiracles as vapor n Distribution Metabolic q Through the body to target sites Enzymes n Metabolism (Break down) q By insect defense mechanisms n Excretion
3 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides act on key functional proteins that regulate vital processes
Target protein e.g. ion channel
binding pocket Small molecule insecticide Insecticides act on key functional proteins that regulate vital processes Altered protein function 1. A protein can have more than one binding pocket for small molecules Altered 2. Specific binding pockets can accommodate biological chemicals with different structures response
4 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright The Pro-Insecticide concept
A Pro-Insecticide might have negligible activity on the target protein due to protecting groups, but can get metabolized in vivo to its active form. This can be a tool to: • Improve bioavailability Pro-Insecticide Metabolic Enzyme(s) • Enable selective toxicity
Insecticide
Target protein
Altered protein function
5 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Major mechanisms of Insecticide Resistance
Metabolic Resistance Metabolic Enzymes and/or
Target Insecticide protein
Target Site Resistance Insecticide
Genetic modifications of Altered Target the target that interfere with target protein binding of the Insecticide protein
6 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Key functional proteins that are targets for Insecticides
Ion channels Enzymes Receptors
essential for signal biocatalysts bioelectricity transducer
ligand
+ Na+ Ca2+ K+ - or Cl Proteins accelerating chemical reactions Binding of a ligand triggers a response
7 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticide Mode of Action Major classes
Nerve & Muscle
Growth
Respiration
Midgut
Unknown or Non-Specific
8 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Ion channels are important targets of neuromuscular disruptors
Na+ Ca2+ Cl-
Cells are surrounded by a cell membrane, which acts - - - like an insulator separating two conducting media
K+ Large organic An asymmetric separation of charges across the cell anions membrane makes the inside negative compared to the outside of the cell (membrane potential)
Ion channels are pore-forming membrane Na+, Ca2+ proteins that transduce signals by controlling the flux or Cl- of ions across the cell membrane. Their concentration gradients together with the membrane potential • Gating: Trigger for channel determine the direction of ion flux. opening (voltage, ligand, etc.) • Ion selectivity: Ion preference In electrically excitable cells (neurons, muscle cells) of the channel ion channels play an important role in fast signal transduction over long distances
9 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright The Insect Neuromuscular system: Translating a stimulus into (muscle) action
Muscle
Stimulus
?
10 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Different types of neurons are involved in signal transduction and fine tuning
Muscle
Stimulus CNS modulatory Ganglion neuron The Central Nervous System (CNS) is the insect’s control center sensory neuron
interneuron
inhibitory neuron
motoneuron
11 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Ion channels play diverse roles within the neuromuscular system
Muscle
CNS Ganglion
12 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Overview of ion channels targeted by neuromuscular disruptors
Muscle
CNS Ganglion
13 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright The TRPV channels exist in specialized sensory neurons that detect stretch
Muscle
CNS modulatory Ganglion neuron
Na+, Ca2+ TRPV sensory neuron
interneuron
inhibitory neuron
motoneuron
14 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright TRPV channels play an important role in insect stretch receptor signaling (Chordotonal Organ)
• Sight Stimulus • Taste • Smell • Touch • Hearing (antenna) Sensed by • Gravity (antenna) • Proprioception* (joints) stretch receptors • Others
sensory neuron *Proprioception is the detection of the relative position and motion of body parts
When a doctor tests Insects also have stretch reflexes with a rubber receptors that detect joint hammer (knee jerk reflex) bending forces local stretch receptors are activated that signal to the spinal cord and back to the target muscle.
15 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on TRPV channels interfere with stretch receptor signaling
n TRPV channel modulators affect Chordotonal organs (COs), stretch receptors in the insect joints that sense relative position of body parts (proprioception)
Leg extension caused by a TRPV modulator (can be imagined as a ‘molecular’ rubber hammer)
n TRPV channels amplify the weak mechanosensory signal in chordotonal neurons
1. Signal detection 2. Signal amplification
Mechano- sensory TRPV channel
n Modulation of TRPV channels generates continuous chordotonal nerve signals independent of joint movement. This leaves insects deaf and uncoordinated, resulting in rapid feeding cessation, leading to starvation and ultimately death 16 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright TRPV channel and chordotonal organ modulators
Group 9: Chordotonal Group 29: organ TRPV channel modulators Chordotonal organ modulators – undefined target site
Pymetrozine
Flonicamid 9B Pyridine Pyrifluquinazon Afidopyropen azomethine derivatives 9D Pyropenes 29 Flonicamid
Flonicamid produces symptoms similar to TRPV channel modulators and like its more active metabolite affects chordotonal organs. However, Flonicamid appears not to act directly on TRPV channels, suggesting a different target site in chordotonal organs.
17 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Overview of ion channels targeted by neuromuscular disruptors
Muscle
CNS Ganglion
18 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on Sodium channels
Muscle
CNS modulatory Ganglion neuron Na+ Sodium Channel
sensory neuron
interneuron
inhibitory neuron
motoneuron
19 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Sodium channels play a crucial role in signal propagation in excitable cells
Axons are long cable-like parts of the neuron that carry electrical signals to a junction with another cell Na+ Voltage-dependent sodium Sodium channels contain a built-in Channel voltage sensor which detects local positive changes in membrane potential
This triggers opening of the channels and sodium entry
Entry of sodium results in a more positive membrane potential that in turn activates adjacent sodium channels thus propagating the signal along the axon
20 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Sodium channel modulators & blockers
Sodium channel mm odulators Sodium channel b lockers
Closed Open Open Closed m b m b
Na+ Na+ Na+
• prolonged opening of sodium channels • obstruction of the sodium channel • prolonged action potentials pore • restimulation of the nerve and repetitive firing • block of nerve action potentials • hyperexcitation • paralysis
21 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on Sodium channels
Group 3: Sodium channel modulators
Esfenvalerate Permethrin Bifenthrin DDT
Deltamethrin lambda- cyhalothrin Methoxychlor alpha- Etofenprox cypermethrin Tefluthrin 3B DDT, Methoxychlor
3A Pyrethroids Pyrethrins (Only major representatives of group 3A are shown)
Group 22: Voltage-dependent sodium channel blockers
Indoxacarb
Metaflumizone
22A Oxadiazines 22B Semicarbazones
22 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Overview of ion channels targeted by neuromuscular disruptors
Muscle
CNS Ganglion
23 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on nicotinic Acetylcholine receptors (nAChR)
Muscle
External stimulus CNS modulatory Ganglion neuron
sensory neuron
Acetylcholine interneuron
inhibitory neuron
Na+, Ca2+ nAChR motoneuron
24 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on nicotinic Acetylcholine receptors (nAChR)
Neurotransmitters such as Acetylcholine bridge the signaling gap (synapse) between excitable cells (neurons, muscle cells) Acetylcholine-filled vesicles
2+
, Ca +
Na 2+ , Ca +
Na
2+
, Ca ,
+ Na • Most fast excitatory synapses in the insect CNS use Acetylcholine as the neurotransmitter
• Synaptic vesicles store Acetylcholine that can be released into the synapse in response to nerve impulses and in turn activate postsynaptic nAChRs 25 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on nAChR
Can cause nAChR competitive modulators hyperexcitation • Bind to the same site as acetylcholine and/or • desensitize nAChR inhibitory paralysis
c c nAChR allosteric nAChR channel modulators b m blockers • Bind to the acetylcholine- • Obstruct the pore and opened channel form at a prevent ion flow different (allosteric) site and • prevent acetylcholine keep channels open signal transduction Na+, Ca2+ Can cause hyperexcitation nAChR and contractive paralysis Can cause flaccid paralysis
26 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Summary of Insecticides acting on nicotinic Acetylcholine receptors (nAChR)
Group 4: Nicotinic acetylcholine receptor (nAChR) competitive modulators
Dinotefuran
Nicotine 4B Sulfoxaflor 4C Nicotine Sulfoximines Acetamiprid Nitenpyram
Imidacloprid Thiamethoxam
4A 4D 4E Clothianidin Thiacloprid Flupyradifurone Triflumezopyrim Neonicotinoids Butenolides Mesoionics
Group 5: Nicotinic Group 32: Nicotinic Group 14: Nicotinic acetylcholine receptor (nAChR) channel blockers acetylcholine receptor acetylcholine receptor Spinetoram (nAChR) allosteric (nAChR) allosteric major component R = H 5,6 single modulators - site I modulators - site II O S minor component R = CH3, 5,6 double S S O S S N Spinosad S O NH SO Na N S 2 3 major component R = H O O S minor component R = CH S 3 GS-omega/kappa Bensultap Thiocyclam S NH2 S HXTX-Hv1a N N SO3Na peptide H Cl O 5 Spinosyns 14 Nereistoxin Cartap Thiosultap- analogues hydrochloride sodium
27 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Overview of ion channels targeted by neuromuscular disruptors
Muscle
CNS Ganglion
28 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on GABA-gated chloride channels (GABA-Cl)
Muscle
External stimulus CNS modulatory Ganglion neuron
sensory neuron
interneuron GABA
inhibitory neuron
- motoneuron Cl GABA-Cl
29 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on GABA-gated chloride channels (GABA-Cl)
GABA
-
Cl Cl- GABA-Cl
- inhibitory
Cl neuron -
• GABA is a major inhibitory Cl neurotransmitter in the CNS and neuromuscular synapses
• Influx of the negatively charged Cl- ions has an inhibitory effect, counteracting excitatory signals
30 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on GABA-gated chloride channel (GABA-Cl)
GABA-Cl antagonists GABA GABA GABA-Cl allosteric modulators • Block the pore and m b prevent chloride influx, • Binding of modulators interfering with the negatively affects GABA-Cl, channel’s inhibitory interfering with the channel’s - function Cl inhibitory function GABA-Cl
Pore blockers and negative modulators both cause convulsions and death
31 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Summary of Insecticides acting on GABA-Cl
Group 2: GABA-gated chloride channel antagonists
Ethiprole Fipronil Chlordane Endosulfan
2A Cyclodiene Organochlorines 2B Phenylpyrazoles (Fiproles)
Group 30: GABA-gated chloride channel allosteric modulators
Fluxametamide Broflanilide Meta-diamides & Isoxazolines
32 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Overview of ion channels targeted by neuromuscular disruptors
Muscle
CNS Ganglion
33 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on Glutamate-gated chloride channels (GluCl)
Muscle
External stimulus CNS modulatory Ganglion neuron
sensory neuron
interneuron Glutamate
inhibitory neuron
Cl- motoneuron GluCl
34 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Allosteric modulators of Glutamate- gated chloride channels (GluCl)
Glutamate
m
Cl- GluCl
• Inhibitory Glutamate-gated chloride channels (GluCl) are widespread on insect nerve and muscle cells and likely function in inhibitory neurotransmission • GluCl modulators activate chloride influx, causing flaccid paralysis
35 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Allosteric modulators of Glutamate- gated chloride channels (GluCl)
Group 6: Glutamate-gated chloride channel (GluCl) allosteric modulators
major component R2 = Ethyl Abamectin R1 = minor component R2 = Methyl
O
HO
O O
H O O H N Lepimectin O R Emamectin H O benzoate R1 = N H O O Milbemectin O O O O OH H O R H O
O O O OH H H OH 6 Avermectins & Milbemycins O major component R = Ethyl H minor component R = Methyl OH
36 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Overview of ion channels targeted by neuromuscular disruptors
Muscle
CNS Ganglion
37 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticides acting on the Ryanodine Receptor (RyR) Ca2+ Muscle External stimulus CNS modulatory Ganglion neuron
Ca2+ RyR
sensory neuron
interneuron
inhibitory neuron
motoneuron
38 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright The Ryanodine receptor (RyR) plays a crucial role in insect muscle contraction
motoneuron • Ca2+ ions entering the muscle cell terminal activate RyR located on the muscle cell’s intracellular Ca2+
Glutamate-filled store to release Ca2+ into the vesicle cytoplasm • The rise in Ca2+ activates more RyRs, leading to massive Ca2+ Excitatory glutamate release receptors • This in turn induces shortening of + Na Na+ Ca2+ Voltage-gated Ca2+ calcium channels contractile filaments, leading to Ca 2+ 2+ Ca2+ muscle cell contraction Ca2+ Ca Ca2+ Ca2+ Ca2+ • RyR modulators open the Muscle filaments RyR Ca2+ ryanodine receptor independent 2+ Ca2+ Ca2+ Ca Ca2+ Ca2+ 2+ of cytoplasmic calcium levels Ca2+ Ca2+ Ca 2+ Ca Ca2+ causing uncontrolled muscle Ca2+ contraction, paralysis and death muscle cell
39 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright RyR modulators
Group 28: Ryanodine receptor modulators
Chlorantraniliprole R=Cl Cyantraniliprole R=CN
Cyclaniliprole
Flubendiamide
28 Diamides Tetraniliprole
40 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Enzymes targeted by neuromuscular disruptors
Muscle
CNS modulatory Ganglion neuron
Acetylcholine- esterase AChE
41 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Acetylcholinesterase (AChE) degrades Acetylcholine in the synapse
Acetylcholinesterases Acetyl choline degrade Acetylcholine in order to terminate the signal after it has been AChE sent across the synapse
Acetate + choline
Acetylcholine-filled AChE vesicles
2+ AChE inhibitors bind to the active site of the
, Ca enzyme preventing Acetylcholine from +
Na binding nAChR 2+
, Ca Acetyl choline + Na -I
AChE
2+ , Ca ,
+ AChE Na
AChE
Acetate + choline
42 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Acetylcholinesterase (AChE) inhibitors
Group 1: Acetylcholinesterase (AChE) inhibitors
Acephate Methamidophos Aldicarb Oxamyl
Methiocarb Fenitrothion
Thiodicarb Carbaryl Chlorpyrifos Profenofos
Methomyl Malathion
Carbofuran Pirimicarb (Only major representatives Dimethoate of the groups are shown) Triazophos
1A Carbamates 1B Organophosphates
43 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Receptors targeted by neuromuscular disruptors Octopamine receptor Muscle
CNS modulatory Ganglion neuron
44 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Octopamine receptor signalling
a-adrenergic-like (OctaR) • Octopamine is the major modulatory neurotransmitter in g PIP2 aq DAG insects; it can increase the b PLC general level of arousal like adrenaline does in mammals IP Ca2+ 3 • Upon release, Octopamine Ca2+ binds to G-protein-coupled
Ca2+ IP3R Receptors (GPCRs) on the Octopamine Ca2+ postsynaptic membrane, which Ca2+ Ca2+ 2+ Ca2+ Ca can be coupled via G-proteins receptors Ca2+ Ca2+ Ca2+ (abg) to Phospholipase C (PLC), Ca2+ Ca2+ an enzyme catalyzing the
formation of IP3, which in turn can activate intracellular Ca2+ ATP release channels. Other cAMP octopamine receptors are b coupled to adenylyl cyclase (AC) as g AC to stimulate cAMP production • Octopamine receptor agonists b-adrenergic-like can mimic the action of this (OctbR) neurotransmitter
45 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Octopamine receptor agonists
Group 19: Octopamine receptor agonists
Amitraz
19 Amitraz
46 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Targets of Neuromuscular Disruptors & Their key Physiological Roles
TRPV Sodium nAChR GABA-Cl GluCl RyR Channel Channel
Excitatory Inhibitory Inhibitory Action potential Muscle Proprioception neuro- neuro- neuro- propagation contraction transmission transmission transmission
Acetylcholin- Octopamine esterase Receptor Excitatory Excitatory neurotransmission neurotransmission
47 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticide Mode of Action Major classes
Nerve & Muscle
Growth
Respiration
Midgut
Unknown or Non-Specific
48 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Growth & Development Disruptors Background
The insect’s skeleton is external (exoskeleton) and contains chitin. Since the exoskeleton cannot expand, it must be replaced with a larger one by the process of molting as the insect grows, requiring chitin synthesis. Molting is under strict hormonal control:
Ecdysone Juvenile Hormone (JH) Egg Molt Ecdysone is released Molt JH prevents molting to by the prothoracic JH levels Larval a more mature stage gland in the thorax Molt Instars JH production stops Pulses of Ecdysone Pupation during metamorphosis induce molting Pupa Ecdysone releases Ecdysone
Metamorphosis Adult
49 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Targets of Growth & Development Disruptors
Juvenile Ecdysone Hormone Receptor NHRs alter the expression of genes needed for ecdysis (EcR) or to form adult structures (JHR) Receptor Ecdysone JH
EcR JHR mRNA NHR Pulses of Protein JH prevents Ecdysone molting to a induce more mature molting stage
EcR agonists directly and persistently JH mimics activate the JH receptor and activate Ecdysone receptors causing the strongly suppress the development of insect to go into a precocious, incomplete adult characteristics keeping the insect in molt, leading eventually to death an ‘immature’ state
50 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Juvenile hormone mimics
Group 7: Juvenile hormone mimics
Hydroprene R1 = ethyl, R2 = H Methoprene R1 = isopropyl, R2 – OCH3
Fenoxycarb Pyriproxyfen Kinoprene R1 = propargyl, R2 = H
7A Juvenile hormone analogues 7B Fenoxycarb 7C Pyriproxyfen
Ecdysone receptor agonists
Group 18: Ecdysone receptor agonists
Chromafenozide Methoxyfenozide
Halofenozide Tebufenozide 18 Diacylhydrazines
51 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Targets of Growth & Development Disruptors
Chitin synthase
• Chitin is a polymer of N-Acetyl glucosamine (NAcGlc; ) ChS • Chitin synthase uses activated NAcGlc (UDP-NAcGlc; UDP ) to extend the growing chitin chain UDP UDP • The nascent chain is released into the extracellular space • Interfering with chitin synthesis results in a weak and soft exoskeleton as well as deformed appendages and sexual organs
52 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Chitin synthesis inhibitors
Group 10: Mite growth inhibitors affecting CHS1
Diflovidazin
Etoxazole Clofentezine Hexythiazox 10B Etoxazole 10A Clofentezine, Diflovidazin, Hexythiazox
Group 15: Inhibitors of chitin biosynthesis affecting CHS1 Group 16: Inhibitors of chitin biosynthesis, type 1
Diflubenzuron Lufenuron Teflubenzuron
Buprofezin Flufenoxuron Novaluron 16 Buprofezin 15 Benzoylureas (Only major representatives of group are shown)
53 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Targets of Growth & Development Disruptors
• ACCase (acetyl CoA ACCase carboxylase) catalyzes the first and rate-limiting step of CO2 Acetyl Malonyl fatty acid biosynthesis CoA CoA Acetyl CO2 • ACCase inhibitors prevent CoA biosynthesis of fats needed COOH for growth and development resulting in incomplete molts and desiccation of the insect Fatty acid
54 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Inhibitors of acetyl CoA carboxylase
Group 23: Inhibitors of acetyl CoA carboxylase
Spiromesifen
Spirodiclofen Spirotetramat
23 Tetronic & Tetramic acid derivatives
55 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Overview Growth & Development Targets
Juvenile Ecdysone Hormone Receptor Receptor Ecdysone JH
EcR mRNA JHR NHR Protein Pulses of JH prevents Ecdysone molting to a induce more mature molting NHRs alter the expression of genes needed for stage ecdysis (EcR) or to form adult structures (JHR)
Chitin Acetyl CoA synthase ChS carboxylase
Chitin synthesis Fatty acid synthesis
56 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticide Mode of Action Major classes
Nerve & Muscle
Growth
Respiration
Midgut
Unknown or Non-Specific
57 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Respiration and Energy Conservation Background
Cells get the energy they need by "oxidizing" food such as fat and sugars to produce carbon dioxide and water. In the cell this process is conducted in many steps in which oxygen is added to the fuel (from water) and hydrogen is removed so that the fuel is converted to carbon dioxide.
The hydrogen is removed by adding it to NAD (a form of vitamin B3) forming NADH. The regeneration of NAD requires oxygen, produces water and releases a lot of energy. Mitochondrion
Most of these steps are contained in a special part of the cell called the mitochondrion. The mitochondrion has a closed membrane system that allows the energy released to be captured by generating ATP which fuels many cellular processes.
58 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright A number of complex proteins are needed to conserve the energy available
+ H H+ H+ H+ H+ H+ + + H H+ H H+ H+
H+
e- e- e- e- e- e- e- H+ Complex I Complex IV e- Complex III ATP Complex II synthase (V)
H2O NADH e- O2 NAD ADP H+ +Pi ATP Inner membrane Inner Outer mitochondrial membrane Outer mitochondrial
NADH oxidation at Complex I Electron flow e - initiated by NADH The enzyme ATP is dependent on an electron oxidation drives consumption of synthase (Complex V) is transfer chain mostly oxygen at Complex IV and the driven by the proton contained within Complex I, pumping of protons H+ across the gradient and catalyzes the Complex III and Complex IV membrane formation of ATP
The enzyme succinate dehydrogenase (Complex II) feeds electrons into the chain and is also required for the overall process of food oxidation.
59 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright How insecticides interfere with cellular respiration:
H+ + H+ H H+ H+ H+ + + H H+ H H+ H+
H+
e- e- e- e- e- e- e- H+ Complex I Complex IV e- Complex III ATP Complex II synthase (V)
H2O NADH e- O2 NAD ADP H+ +Pi ATP Inner membrane Inner Outer mitochondrial membrane Outer mitochondrial
Inhibitors of one of the electron transport complexes I-IV or the mitochondrial ATP synthase (Complex V) starve cells of energy by preventing ATP formation, resulting in paralysis
60 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Inhibitors of Complexes I-V
Group 21: Mitochondrial complex I electron transport inhibitors Group 25: Mitochondrial complex II electron transport inhibitors
CN N N
O O
Rotenone Fenazaquin Pyrimidifen Cyenopyrafen 25A beta- Ketonitrile 21B Rotenone F3C O derivatives Pyridaben Tolfenpyrad NC O Pyflubumide
O 21A METI O 25B Carboxanilides Fenpyroximate acaricides and Tebufenpyrad Cyflumetofen insecticides
Group 20: Mitochondrial complex III electron transport inhibitors Group 24: Mitochondrial complex AlP IV electron transport inhibitors
O Aluminium O CF O Hydramethylnon O 3 O HN NH phosphide Zn3P2 - F3C O HN CN N O O N N N H O O N O Zinc O phosphide Cyanide Ca3P2 salts Acequinocyl Fluacrypyrim Bifenazate PH3 CF3 Calcium phosphide 24A Phosphine 24B Cyanides 20A Hydramethylnon 20B Acequinocyl 20C Fluacrypyrim 20D Bifenazate Phosphides
Group 12: Inhibitors of mitochondrial ATP synthase
O O O O S Sn O O O S Cl S Sn Sn O N N N H H N Cl Cl Cl N Fenbutatin Azocyclotin Propargite Tetradifon Diafenthiuron oxide Sn 12A Diafenthiuron OH 12B Organotin 12C Propargite 12D Tetradifon Cyhexatin miticides
61 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright How insecticides interfere with cellular respiration:
H+ H+ H+ H+ + H H+ H+
e- e- e- e- e- e- e-
Complex I Complex IV e- Complex III H+ ATP Complex II synthase (V) H+ H2O H+ NADH e- O2 H+ NAD H+ ADP +Pi ATP H+ Inner membrane Inner Outer mitochondrial membrane Outer mitochondrial
have the ability to carry protons across the inner mitochondrial membrane, thus removing the proton gradient è ATP synthase is no longer able to provide cellular ATP è O2 consumption is accelerated
62 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Uncouplers
Group 13: Uncouplers of oxidative phos- phorylation via disruption of proton gradient
Br CN
F3C N
O Cl OH
O2N Chlorfenapyr Sulfluramid
NO2
DNOC
13 Pyrroles, Dinitrophenols, Sulfluramid
63 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticide Mode of Action Major classes
Nerve & Muscle
Growth
Respiration
Midgut
Unknown or Non-Specific
64 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright The insect midgut as a target for insecticidal agents
• Released in the insect midgut upon ingestion of ‘packaged forms’ Bacillus • Cause lysis of midgut epithelial cells thuringensis Baculoviruses via different mechanisms derived toxins • Result in loss of midgut integrity and ultimately death of the pest insect
Midgut cells
Hindgut Foregut
Midgut
65 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Mode of Action of Bacillus thuringiensis Cry Toxins on Midgut Epithelium
1. crystal solubilization 2. protoxin proteolytic activation 3. activated toxin monomer binding to cadherin & cleavage of helix α-1 4. pre-pore tetrameric structure formation 5. tetramer binding to aminopeptidase-N or alkaline phosphatase 6. pore formation.
66 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Microbial disruptors of insect midgut
Group 11: Microbial disruptors of insect midgut membranes
Includes transgenic crops expressing Bacillus thuringiensis toxins (however, specific guidance for resistance management of transgenic crops is not based on rotation of modes of action)
Bacillus thuringiensis and the insecticidal proteins produced
B.t. israelensis, B.t. aitzawai, B.t. kurstaki, B.t. tenebrionis Bacillus sphaericus Bt crop proteins* Cry1Ab, Cry1Ac, Cry1Fa, Cry1A.105, Cry2Ab, Vip3A, mCry3A, Cry3Ab, Cry 3Bb, Cry34Ab1/Cry35Ab1
11A Bacillus thuringiensis 11B Bacillus sphaericus
Different B.t. products that target different insect orders may be used together without compromising their resistance management.
Rotation between certain specific B.t. microbial products may provide resistance management benefits for some pests. Consult product-specific recommendations.
* Where there are differences among the specific receptors within the midguts of target insects, transgenic crops containing certain combinations of these proteins provide resistance management benefits.
67 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Mode of Action of Baculoviruses on Midgut Epithelium
1. Viral occlusion body disintegrates in alkaline midgut 2. Released occlusion derived virus passes through the peritrophic membrane to bind to species-specific receptors on the microvilli of midgut columnar epithelial cells 3. Viral envelope fuses with cell membrane releasing nucleocapsids in the cells 4. Entry mediated by viral proteins called per os infection factors (PIF 0-8)
From Boogaard et al., 2018 Insects 9, 84
68 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Baculoviruses acting on insect midgut
31 Baculoviruses
Anticarsia Cydia pomonella GV gemmatalis MNPV
Thaumatotibia Helicoverpa leucotreta GV armigera NPV
Granuloviruses & Nucleopolyhedroviruses
69 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticide Mode of Action Major classes
Nerve & Muscle
Growth
Respiration
Midgut
Unknown or Non-Specific
70 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Non-specific (multi-site inhibitors)
Group 8: Miscellaneous non-specific (multi-site) inhibitors
Methyl bromide Cryolite Dazomet Na2B4O7·10H2O 8A Alkyl halides Borax Tartar emetic
8D Borates 8E Tartar emetic Sulfuryl fluoride Metam
8C Fluorides Chloropicrin 8F Methyl isothiocyanate generators 8B Chloropicrin
Unlike many other insecticides and miticides, non-specific or multi-site inhibitors do not act on a distinct target site but likely disrupt a variety of important physiological functions.
71 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Insecticidal agents of unknown MoA
Group UN: Compounds of unknown or uncertain MoA
O O O OH OH O Cl O O Dicofol Bromopropylate O O Cl O O Cl Cl O H H N Cl O Cl CF3 O OH OH O O O Azadirachtin CCl3 Pyridalyl
O N S S O N O O CaSX Cl O N S (Lime sulfur) O Chinomethionat Sulfurs Benzoximate Mancozeb
Group UNB: Group UNE: Group UNF: Group UNM: Bacterial agents Botanical essence including Fungal agents of Non-specific (non-Bt) of unknown or synthetic, extracts and unknown or uncertain mechanical disruptors uncertain MoA unrefined oils with unknown MoA or uncertain MoA
Chenopodium ambrosioides Beauveria bassiana strains near ambrosioides extract Metarhizium anisopliae strain F52 Burkholderia spp, Fatty acid monoesters with Paecilomyces fumosoroseus Diatomaceous earth Wolbachia pipientis (Zap) glycerol or propanediol Apopka strain 97 Neem oil
Compounds with the unknown designation may act on a distinct target site, but the mechanism of action has not been conclusively determined. Because of their non-specific or unknown MoA, active ingredients in IRAC MoA groups 8 (non-specific, multi-site inhibitors), 13 (uncouplers of oxidative phosphorylation), and all UN groups (UN, UNB, UNE, UNF, UNM) are thought not to share a common target site and therefore may be freely rotated with each other unless there is a reason to expect cross-resistance.
72 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright 73 Details are accurate to the best of our knowledge but IRAC and its member companies cannot accept responsibility for how the information is used or interpreted. Protected by © Copyright Important links
https://www.irac-online.org/
Modes of Action
Pests Crops Teams Test Methods News
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