new chemistries for insect management
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Introduction
IntroductionInsects damages crops
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Drawbacks of existing insecticides
Classification Of Old Insecticides
Organochlorines(DDT, aldrin,HCH, endrin)
Organophosphates
(dichlorvos, parathion,
chlorpyrifos, acephate)
Carbamates(carbaryl, aldicarb,isolan, carbofuran)
Sythetic pyrethroids
(allethrin, cypermethrin,
cyfluthrin, fluvalinate)Indi
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Problems Of Old Insecticides
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Residue
Resistance
Resurgence
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New Chemistr
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New Chemistries ForInsect Management
Seminar (AC 691)Prithusayak Mondal
Division Of Agricultural ChemicalsPh.D. Research Scholar (10064)
I.A.R.I., New Delhi 110012
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Outline
Selectivity
New Insecticide Classes• Neonictinoids• Phenyl pyrazoles• Oxadiazines• Halogenated pyrroles• Thiourea derivatives• Quinazolines• Pyridazinones• Thiazolidines• Carbazates• Diamides• IGRs (Benzoyl ureas, Thiadiazines)• Diacylhydrazines• New insecticides from microorganisms (Avermectins, Spinosyns, B. thuringiensis, M. anisopliae)
• Pyridine azomethines• Tetronic acid derivatives• Sulfoximes (Sulfoxaflor)
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Neo-nicotinoidsSynthetic analogues of nicotine
Drawbacks of nicotine- Expensiveness- Lack of commercially applicable synthesis- Extreme toxicity to mammals- Limited insecticidal spectrum
Introduction of new nicotine like compounds 4 groups
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Chloronicotinyl compounds
Thionicotinyl compounds Furanicotinyl compounds Pyridincarboxamides
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Chloronicotinyl Compounds
ImidaclopridIUPAC: (E)-1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin- 2-ylideneamine
systemic insecticide having good xylem mobility and used as seed treatment, soil and foliar application
Formulations: 17.8% SL (Confidor®), 70% WS (Gaucho®)
Effective against sucking pests (aphids, leaf hoppers, plant hoppers, whiteflies, thrips)Indi
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Acetamiprid Imidacloprid Nitenpyram
ClothianidinIUPAC: (E)-1-(2-chloro-1,3-thiazol-5-ylmethyl)-3-methyl-2- nitroguanidine
Broad spectrum insecticide Formulations: 48% FC (Poncho®) Effective against hemipteran, thysanopteran and
coleopteran sucking insect pests
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Thionicotinyl Compounds
Clothianidin Imidaclothiz Thiacloprid
Thiamethoxam
Furanicotinyl compoundsDinotefuran
IUPAC: (EZ)-(RS)-1-methyl-2-nitro-3-(tetrahydro-3-furylmethyl)guanidine
Highly systemic insecticide Formulations: 20% SG (Token®) Effective against sucking pests (hoppers, jassids,
aphids)
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Dinotefuran
PyridincarboxamidesFlonicamid
IUPAC: N-cyanomethyl-4-(trifluoromethyl)nicotinamide
Systemic and trans-laminar activity; long time protection; feeding deterrent
Formulations: 50% WG (Ulala®) Effective against major species of aphids; also
controls mealy bugs, whiteflies, plant hoppers
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Flonicamid
Mode Of Action They are nicotinic acetylcholine receptor agonists
They bind strongly to nicotinic acetylcholine receptors (nAChRs) in the central nervous system of insects, causing nervous stimulation at low concentrations, but receptor blockage, paralysis and death at higher concentrations
Neonicotinoids bind more strongly to insect nAChRs than to those of vertebrates, so they are selectively more toxic to insects
(Tomizawa & Casida,
2005)
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Phenyl pyrazolesFipronil
IUPAC: (±)-5-amino-1-(2,6-dichloro-α,α,α-trifluoro-p-tolyl)-4- trifluoromethylsulfinylpyrazole-3-carbonitrile
Systemic insecticide with contact and stomach action Formulations: 5% SC (Regent®) It controls stem borers, gall midge, DBM, thrips, root
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Acetoprole Ethiprole Fipronil Flufiprole Pyraclofos Pyrafluprole Pyriprole Pyrolan Vaniliprole
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Mode Of Action Acts as an inhibitor at the γ-aminobutyric acid (GABA)
receptor as a non-competitive blocker of the GABA-gated chloride channel (similar to lindane and cyclodienes)
Chemical and biological activation producing equally toxic and sometime more persistent metabolites with same mode of action
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Cl-
Cl-Cl-
Na+
Cl-
Fipr
K+
Antagonist at GABA-gated Chloride Channel
OxadiazinesIndoxacarb
IUPAC: Methyl 7-chloro-2,5-dihydro-2-[[(methoxycarbonyl)[4-(trifluoromethoxy)phenyl]amino]carbonyl]indeno[1,2-e] [1,3,4]oxadiazine-4a(3H)-carboxylate
Formulations: 15.8% EC (Avaunt®) Effective against lepidopteran pests (American boll
worm, DBM, Helicoverpa armigera, Plutella xylostella)
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Indoxacarb
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Mode Of Action This pro-insecticide is bioactivated in the insect by
enzymatic (insect esterase) N-decarbomethoxylation changing it to a more active, highly insecticidal metabolite
It produces its potent effects at a unique binding site in voltage-gated sodium ion channels of the nervous system of susceptible insects
The active metabolite of indoxacarb induces irreversible hyperpolarization of insect nerve cell membranes. It blocks the sodium current amplitude in the neuron differently than the pyrethroids
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Halogenated pyrrolesChlorfenapyr
IUPAC: 4-Bromo-2-(4-chlorophenyl)-1-ethoxymethyl-5-trifluoromethyl- 1H-pyrrole-3-carbonitrile
Formulations: 10% SC (Intrepid®) Effective against DBM in cabbage and cauliflower, mites in
chilli
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Chlorfenapyr
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Mode Of Action Chlorfenapyr works by disrupting the production of ATP,
specifically, Oxidative removal of the N-ethoxymethyl group of chlorfenapyr by MFO forms the compound CL 303268 which uncouples oxidative phosphorylation at the mitochondria, resulting in disruption of production of ATP, cellular death, and ultimately organism mortality
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Oxidative phosphorylation Uncouplers
Thiourea derivativesDiafenthiuron
IUPAC: 1-tert-butyl-3-(2,6-diisopropyl-4-phenoxyphenyl)thiourea
Formulations: 50% WP (Polo®) Effective against sucking insects (whiteflies, aphids,
jassids), mites, capsule borers
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Diafenthiuron
5
QuinazolinesFenazaquin
IUPAC: 4-tert-butylphenethyl quinazolin-4-yl ether
Formulations: 10% EC (Magister®) Mode of action: Broad spectrum acaricide; It inhibits
mitochondrial electron transport chain by binding with complex I at co-enzyme Q
Effective against mites in tea and chilliIndi
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Fenazaquin
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PyridazinonesFenpyroximate
IUPAC: tert-butyl (E)-α-(1,3-dimethyl-5-phenoxypyrazol-4-ylmethyleneamino-oxy)-p-toluate
Formulations: 5% EC (Mitigate®) Effective against red spider mites and two spotted mites
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Fenpyroximate Pyridaben Pyridalyl
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It is photochemically converted in sunlight to its carbodiimide derivative, which is a more powerful toxicant than diafenthiuron
(Steinmann et al., 1990)
The carbodiimide acts as an adenosine triphosphatase (ATPase) inhibitor following metabolic activation to the corresponding carbodiimide
(Petroske and Casida, 1995)
The carbodiimide metabolite inhibits mitochondrial respiration by selective and covalent binding to the proteolipid ATPase
(Ruder et al., 1992; Kayser and Eilinger, 2001)
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ThiazolidinesHexythiazox
IUPAC: (4RS,5RS)-5-(4-chlorophenyl)-N-cyclohexyl-4-methyl-2-oxo- 1,3-thiazolidine-3-carboxamide
Formulations: 5.45% EC (Maiden®) Mode of action: Unknown or non-specific mode of action
(mite growth inhibitors) Effective against red spider and yellow mites in tea and
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Hexythiazox
CarbazatesBifenazate
IUPAC: Isopropyl 2-(4-methoxybiphenyl-3-yl)hydrazinoformate
Selective acaricide Formulations: 24% SC (Floramite®) Mode of action: Neuroactive; exact mode of action is
unclear Effective against spider miteIn
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Bifenazate
DiamidesFlubendiamide
IUPAC: 3-iodo-N’-(2-mesyl-1,1-dimethylethyl)-N-{4-[1,2,2,2-tetrafluoro-1-trifluoromethyl)ethyl] -o-tolyl}
phthalamide
Pthalic diamide Formulations: 20% WG (Takumi®), 39.35% SC (Fame®) Effective against insect pests of rice (stem borer. Leaf
folder) and cotton (Helicoverpa armigera, spotted boll worm)
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Flubendiamide Chlorantraniliprole
Cyantraniliprole
Cyclaniliprole Tetraniliprole
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Diamides …Cyantraniliprole
IUPAC: 3-bromo-1-(3-chloro-2-pyridyl)-4′-cyano-2′-methyl-6′- (methylcarbamoyl)pyrazole-5-carboxanilide
Anthranilic diamide Formulations: 20% SC (Cyazypyr®) Effective against key chewing and sucking insects
(Homopterans and lepidopterans)
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Ryanodine receptors are intracellular Ca2+ channels specialized for the rapid and massive release of Ca2+
from intracellular stores, which is an essential step in the muscle contraction process
Pthalic diamides interacts with a site distinct from the ryanodine binding site and disrupts the Ca2+
regulations of the ryanodine receptor completely by an allosteric mechanism
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Anthranilic diamides cause death of insects by disruption of Ca2+ within muscle tissue.
The anthranilic diamide insecticides bind to ryanodine receptors locking them partially open. Ca2+ leaks out of muscle tissues which results in the inability to regulate muscle function which causes paralysis and death
(Cordova et al., 2006)
Mode Of Action …
Flufenoxuron IUPAC: 1-[4-(2-chloro-α,α,α-trifluoro-p-tolyloxy)-2-fluorophenyl]- 3-(2,6-difluorobenzoyl)urea
Insect growth regulator Formulations: 10% DC (Cascade®) Effective against immature stages of many
phytophagous mites and insects pests of pome fruit, vines, citrus, tea, ornamentalsIn
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iBenzoyl Urea
Bistrifluron Chlorbenzuron Chlorfluazuron
Dichlorbenzuron Diflubenzuron Flucycloxuron Flufenoxuron Hexaflumuron
Lufenuron Novaluron
Noviflumuron Penfluron
Teflubenzuron
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Mode Of Action It acts as a chitin synthesis inhibitor by blocking terminal
polymerization step catalysed by chitin synthase enzyme
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These compounds alters cuticle composition—especially that of chitin—thereby affecting the elasticity and firmness of the endo-cuticle
(Grosscurt & Anderson, 1980)
The reduced level of chitin in the cuticle seems to result from inhibition of biochemical processes leading to chitin formation
(Hajjar & Casida, 1979)
They might affect the insect hormonal site, thereby resulting in physiological disturbances such as inhibition of DNA synthesis, alter carbohydrase and phenoloxidase activities, or suppress microsomal oxidase activity
(Ishaaya & Ascher, 1977; Van Eck, 1979; Soltani et al., 1984)
They inhibit 20E-dependent GlcNAc incorporation into chitin
(Oberlander & Silhacek, 1998)
ThiadiazinesBuprofezin
IUPAC: (Z)-2-tert-butylimino-3-isopropyl-5-phenyl-1,3,5-thiadiazinan-4-one
Insect growth regulator Formulations: 44% SC (Applaud®) Effective against homopteran insects (hoppers, jassids,
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Buprofezin
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Mode Of Action It acts as a chitin synthesis inhibitor having both contact
and vapour phase activity
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It acts on the nymph stages of leaf hoppers, scales, plant hoppers,and whiteflies
(Ishaaya et al., 1988)
It inhibits incorporation of 3H-glucosamin into chitin
(Uchida et al., 1985)
As a result of chitin deficiency, the pro-cuticle of the nymphs loses its elasticity and the insect is unable to complete the moulting process
(De Cock and Degheele, 1998)
DiacylhydrazinesChromafenozide
IUPAC: N′-tert-butyl-5-methyl-N′-(3,5-xyloyl)chromane-6-carbohydrazide
Insect growth regulator Formulations: 5% SC (Virtu®) Effective against lepidopteran insects on top fruitsIn
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Chromafenozide Halofenozide
Methoxyfenozide Tebufenozide
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Mode Of Action
These compounds bind to the ecdysteroid receptors, accelerating the molting process and thereby disrupting the insect hormonal balance
(Wing, 1988; Palli et al., 1996)
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New Insecticides From Microorganisms
AvermectinsSource: Streptomyces avermitilis
A series of 16-membered macrocyclic lactone derivatives with potent anthelmintic and insecticidal properties
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Abamectin (Avermectin B1) Agri-Mek® 15% ECUsed against sucking pests, phytophagous mites,
dipterans, psyllidae, leaf miners Ivermectin (22,23-dihydroavermectin) Ivomec® 1% S
Used to control parasites of cattle Emamectin benzoate Proclaim® 5% WSG
Used against lepidopteran insects
Mode of actionThey block the transmittance of electrical activity in nerves and muscle cells by stimulating the release and binding of GABA at nerve endings.
This causes an influx of chloride ions into the cells, leading to hyperpolarisation and subsequent paralysis of the neuromuscular systems
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New Insecticides From Microorganisms …
Spinosyns Spinosad 1st a.i. Source: Saccharopolyspora spinosa
Mixture of 2 most active metabolites, Spinosyn A and Spinosyn D
Formulations: 45% SC (Tracer ®)Mode of action
They primarily target binding sites on nicotinic acetylcholine receptors (nAChRs) of the insect nervous system that are distinct from those at which other insecticides have their activity.
Spinosoid binding leads to disruption of acetylcholine neurotransmission. Spinosad also has secondary effects as a GABA neurotransmitter agonist
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New Insecticides From Microorganisms …
Entomopathogenic Bacteria
Bacillus thuringiensis Bacillus thuringiensis (Bt), a gram-positive, motile, rod
shaped bacterium produces a parasporal crystal composed of one or more proteins
The strains of Bt characterized so far affect members of 3 insect orders: Lepidoptera (butterflies & moths), Diptera (mosquitoes & biting flies) and Coleoptera (beetles)
3 Bt products registered in India
B.t. kurstaki is the most commonly used Bt formulation
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B.t. israelensis (diptera)—frequently used for mosquitoes B.t. kurstaki (lepidoptera)—frequently used for gypsy
moth, spruce budworm, and many vegetable pests B.t. galleriae (lepidoptera)—frequently used for leaf beetle,
Colorado potato beetle
Bacillus thuringiensis strains produce crystalline proteins (called δ-endotoxins)Caterpillar consumes the Bt spore (diagram 1) & crystalline toxin-treated leafThe Bt crystalline toxin (diamond shapes in diagram 2) binds to gut wall receptors, and the caterpillar stops feedingWithin hours, the gut wall breaks down, allowing spores (oval tube shapes) and normal gut bacteria (circular shapes) to enter body cavity, where the toxin dissolvesThe caterpillar dies in 24 to 48 hours from septicemia, as spores and gut bacteria proliferate in its blood (diagram 3)
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Entomopathogenic Fungi
Metarhizium anisopliae They cause green muscardine disease in various insect pests
Mode of action Fungi have virulent spores adsorbed to the carrier/neutral
material that remain either dormant or active on the carrier particles and start multiplying when congenial environmental conditions are met with
The soil borne insect like termites come in contact with the fungus and the mycelia of fungus starts growing on the body of termites and starts feeding on the body fluid of insects and results in disease and death of the insect pest
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lhi Conidia Different cultures of M. anisopliae Cockroach killed
by M. anisopliae
Pyridine azomethinesPymetrozine
IUPAC: (E)-4,5-dihydro-6-methyl-4-(3-pyridylmethyleneamino)- 1,2,4-triazin-3(2H)-one
Formulations: 50% WDG (Fulfill®) Mode of action: It has no direct toxicity against insects
but it blocks stylet penetration of sucking insects which may cause immediate cessation of feeding after exposure to this insecticide
Effective against sucking pests (whiteflies, hoppers and aphids)
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Pymetrozine
Tetronic Acid DerivativesSpiromesifen
IUPAC: 3-mesityl-2-oxo-1-oxaspiro[4.4]non-3-en-4-yl 3,3-dimethylbutyrate
Formulations: 24% SC (Oberon®) Mode of action: Prevent Lipid biosynthesis by inhibiting
acetyl CoA carboxylase Effective against mites and moth scale insectsIn
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Spiromesifen
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SulfoximinesSulfoxaflor
IUPAC: [methyl(oxo){1-[6-(trifluoromethyl)-3-pyridyl]ethyl}-λ6-sulfanylidene]cyanamide
Systemic insect neuro-toxin Formulations: 24% SC (Transform®) Effective against major species of sap feeding
insects
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Sulfoxaflor
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Mode Of Action It causes a blockage in the nicotinergic neuronal
pathway leading to the accumulation of acetylcholine, an important neurotransmitter, resulting in the insect's paralysis and eventually death
Sulfoxaflor is stable to monooxygenases that are known to readily metabolize other insecticides such as organochlorines and the neonicotinoids
(Zhu et al., 2011)
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Methoxyacrylates
Naphthoquinones
Nereistoxin analogues
Sulfite esters
BotanicalsMiscellaneous
compounds
Other Insecticidal GroupsIn
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Future Challenges To develop more and more new molecules having
More discoveries in macromolecular pesticides
More innovations required for new neo-nicotinoidsIndi
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Low dose compounds High efficacy and quick knockdown
effect Low mammalian toxicity
Relatively safer formulations Less leaching potential
New chemistry Less harmful to beneficial species
Future Challenges … More biotechnological innovations to be directed in
transgenic plants etc.
More innovative technology to be developed in application of pesticides
Minimization of residue load in ecosystem
More emphasis shall be given in bio-control agents
Research emphasis shall be given in innovations of more plant derived bio-pesticidesIn
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Conclusion Scientific community has been involved in approaches
towards the developments of newer molecules which could be easily biodegradable, target-specific with very low mammalian toxicity
A distinct division in scientific opinion was made to decide whether to go for bio-based products or for using synthetic chemicals for protecting the crops
A new horizon of analytical chemistry was evolved as pesticide residue analysis to judge the residue level of these harmful chemicals in food grainsIn
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Conclusion … Researches were carried out to develop safer molecules
which could undergo photo-degradation, microbial degradation as well as chemical degradation leaving very less amount of residues in the environment
The prime motto for this development is to give protection to the crops along with safety to the natural enemies of different pests as a whole safety to environment
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“If you're not part of the solution, You're part of the precipitate …”
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