Modes of Action of Pesticides

Insecticide and Acaricide Groups Based on Sites of Action

The classification scheme was developed in consultation with the Insecticide Resistance Action Committee (IRAC). IRAC is a Specialist Technical Group of the Global Crop Protection Federation (GCPF).

Most biological insecticides are not included in this table because they don’t pose a great concern for resistance development. Microbial products with Bacillus sp. and azadirachtin (Neem). are included.

Group Site Of Action Chemical Group Active Ingredient

1A1

Acetylcholinesterase inhibitors. Inhibition of the enzyme acetylcholinesterase, interrupting the transmission of nerve impulses

Carbamates

aldicarb

aminocarb

bendiocarb

carbaryl

carbofuran

formetanate hydrochloride

methiocarb

methomyl

oxamyl

pirimicarb

propoxur

1B1

Organophosphates

acephate

azamethiphos

azinphos-methyl

chlorfenvinphos

chlorpyrifos

coumaphos

diazinon

dichlorvos (DDVP)

dimethoate

disulfoton

ethion

fenitrothion

fensulfothion

fenthion

fonofos

malathion

methamidophos

methidathion

naled

oxydemeton-methyl

parathion

phorate

phosalone

phosmet

sulfotep

temephos

terbufos

tetrachlorvinphos

trichlorfon

2A1

Gamma-aminobutyric acid (GABA)-gated chloride channel antagonis. Interferes with GABA receptors of insect neurons, leading to repetitive nervous discharges repetitive nervous discharges

Chlorinated cyclodienes

endosulfan

dienochlor

Polychlorocycloalkanes

lindane

2B1

GABA-gated chloride channel antagonists. Interferes with GABA receptors of insect neurons, leading to repetitive nervous discharges – fiprole site

Phenylpyrazoles *

3

Sodium channel modulators. Acts as an axonic poison by interfering with the sodium channels of both the peripheral and central nervous system stimulating repetitive nervous discharges, leading to paralysis

diphenylethanes

dicofol

methoxychlor

Synethetic pyrethroids

d-allethrin

d-trans allethrin

cyfluthrin

cypermethrin

deltamethrin

fenpropathrin

fenvalerate

flucythrinate

tau-fluvalinate

permethrin

resmethrin

tefluthrin

tetramethrin

Pyrethrins

pyrethrins

4

4 Acetylcholine receptor agonists/antagonists. Binds to nicotinic acetylcholine receptor, disrupting nerve transmission

Chloronicotines (nitroguanidines)

imidacloprid

Nicotine

nicotine

Cartap *

Bensultap *

5

Acetylcholine receptor modulators. Alters acetylcholine receptor site and disrupts binding

Spinosyns

spinosad

6

Chloride channel activators. Interferes with the GABA nerve receptor of insects.

Avermectin

abamectin

Milbemycin *

7

Juvenile hormone mimics (insect growth regulator). Mimic juvenile hormones, which prevent moulting from the larval to the adult stage

Juvenile hormone analogues

methoprene

8A1

Unknown or non-specific site of action (fumigants)

Fumigant

methyl bromide

8B1

aluminum phosphide

9A1

Compounds of unknown or non-specific site of action (feeding disruptors)

Feeding disruptors * (pymetrozine, cryolite)

9B1

10

Compounds of unknown or non-specific site of action (mite growth inhibitors)

Mite growth inhibitors (ovicide)

clofentezine

11

Microbial disruptors of insect mid-gut membranes (includes Cry proteins expressed in transgenic plants). Organism has protein inclusions that are released in the gut of the target pest resulting in gut paralysis and a cessation of feeding

Bt Microbials (biological insecticide/larvicide)

Bacillus thuringiensis var. Aizawai, encapsulated delta endotoxin

Bacillus thuringiensis var. Tenebrionis

Bacillus thuringiensis var. Israelensis

Bacillus thuringiensis var. Kurstaki

12

Inhibition of oxidative phosphorylation at the site of dinitrophenol uncoupling [disrupt adenosine triphosphate (ATP) formation]

Organotin matricides

fenbutatin oxide

13

Uncoupler of oxidative phosphorylation (disrupt H proton gradient formation)

Pyrrole compound * (broad spectrum contact and stomach poison)

14

Inhibit magnesium – stimulated ATPase

Sulfite ester matricides

propargite

15

Inhibit chitin biosynthesis

Substituted benzoylurea

diflubenzuron

16

Inhibit chitin biosynthesis type 1 – Homopteran

Thiadiazine *

17

Inhibit chitin biosynthesis type 2- Dipteran

Triazine

cyromazine

18

Ecdysone agonist/disruptor. Disrupts insect molting by antagonizing the insect hormone ecdysone

Benzoic acid hydrazide

tebufenozide

Botanical * (Neem oil or azadirachtin

19

Octopaminergic agonist

Triazapentadiene

amitraz

20

Site II electron transport inhibitors

None

hydramethylnon

21

Site I electron transport inhibitors

Botanical

rotenone

Pyridazinone

pyridaben

1 Other resistance mechanisms that are not linked to site of action, such as enhanced metabolism, are common for this group of chemicals. All members of this class may not have developed significant cross resistance. When only this group of products are available, alternation of compounds from subgroup A and subgroup B are recommended.  (From www.agf.gov.bc.ca)

 

To understand how pesticides affect insects and other pests go to  “Pest toxicology: the primary mechanisms of pesticide action”  http://www.ncbi.nlm.nih.gov/pubmed/19284791

 

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