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Publication #PI-83

IRAC's Insecticide Mode of Action Classification1

Frederick M. Fishel2

This guide explains the rationale behind the Insecticide Resistance Action Committee's (IRAC) insecticide and acaricide mode of action classification and provides a listing of those insecticide common names with their groupings and primary modes of action for insecticides currently registered in Florida.

What is IRAC?

IRAC has groups formed in several countries, including the United States, Brazil, South Africa, Spain, India, and Australia. The group's purpose is to communicate and educate agricultural producers and crop protection professionals by providing resistance management information. Members of an IRAC group are generally professionals who are actively engaged in the insecticide and acaricide manufacturing industry. Some university researchers also participate.

Resistance to Pesticides

Resistance refers to an inheritable change in the sensitivity of a pest population that is reflected by a repeated product failure to achieve the expected control level when used according to the label recommendation for that pest species. Resistance does not always occur, but it has been documented with insecticides as early as 1914. There are many known instances today where resistance is a problem. Not only has resistance occurred with insecticides, but it has also occurred with other pesticides, such as fungicides, herbicides, and rodenticides. Complicating the understanding and management of resistance is the problem of knowing which type of resistance is present in a given pest population. Some pest populations are known to have cross-resistance. That is, they are not effectively controlled with pesticides having the same mode of action that generally targets the same site within the pest. For example, both the carbamate and organophosphate insecticides target acetylcholine esterase, although each group of insecticides is chemically different from one another. The greatest resistance concern arises when multiple-resistance is confirmed. Multiple-resistance is the situation of a pest population that is resistant to pesticides having different modes of action. It is the most difficult type of resistance to manage because the number of management options is reduced. For more information on resistance, see UF/IFAS EDIS Document ENY-624, 2014 Florida Citrus Pest Management Guide: Pesticide Resistance and Resistance Management, http://edis.ifas.ufl.edu/cg026.

IRAC's Classification Scheme

IRAC's insecticide classification scheme is based on mode of action. The goal of the scheme is to provide information to applicators of acaricides and insecticides, so they can make sound decisions on selecting insecticides to prevent or manage resistance. Besides selecting products that have different modes of action, growers are also encouraged to integrate other methods into insect and mite control programs. Table 1 contains those acaricides and insecticides registered for use in Florida, though it changes constantly. They are listed according to IRAC's classification scheme by their group and subgroup codes, primary target site of action, chemical sub-group or exemplifying active ingredient, and active ingredient, based on that appearing in version 7.3, 2014, prepared by the IRAC International MoA Working Group .

Using the IRAC Classification Scheme with Product Labels

IRAC is currently encouraging manufacturers of pesticides to indicate the IRAC mode of action group number and description on their product labels; some registrants are now doing so, especially with newer products. Such information would be helpful in assisting pesticide applicators in the selection of acaricides and insecticides for use in resistance management strategies. An example of the manner that IRAC is encouraging registrants to list this information is as follows:

Figure 1. 

Additional Information

IRAC: http://www.irac-online.org/groups/guide/

Rogers, M.E., and M. M. Dewdney. 2014. Florida Citrus Pest Management Guide: Pesticide Resistance and Resistance Management. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/cg026.

Tables

Table 1. 

IRAC's classification scheme for acaricides and insecticides registered for use in Florida.

Group

Subgroup

Primary target site of action

Chemical subgroup or exemplifying active ingredient

Active ingredients

1*

1A

Acetylcholine esterase inhibitors

Carbamates

Aldicarb

Bendiocarb

Carbaryl

Carbofuran

Methiocarb

Methomyl

Oxamyl

Propoxur

Thiodicarb

 

1B

 

Organophosphates

Acephate

Chlorpyrifos

Chlorpyrifos-methyl

Coumaphos

Diazinon

Dichlorvos

Dicrotophos

Dimethoate

Disulfoton

Ethoprop

Fosthiazate

Malathion

Methamidophos

Methidathion

Methyl parathion

Naled

Oxydemeton-methyl

Phorate

Profenofos

Propetamphos

Temephos

Terbufos

Tetrachlorvinphos

Trichlorfon

2

2A

GABA-gated chloride channel antagonists

Cyclodiene organochlorines

Endosulfan

 

2B

 

Phenylpyrazoles (Fiproles)

Fipronil

3*

3A

Sodium channel modulators

Pyrethroids

Pyrethrins

Allethrin and isomers

Bifenthrin and isomers

Cyfluthrin and isomers

Cyhalothrin and isomers

Cypermethrin and isomers

Cyphenothrin

Deltamethrin

Esfenvalerate

Fenpropathrin

Fenvalerate

Imiprothrin

Permethrin

Phenothrin

Prallethrin

Pyrethrins (pyrethrum)

Resmethrin

Tefluthrin

Tetramethrin

Tralomethrin

4

4A

Nicotinic acetylcholine receptor agonists

Neonicotinoids

Acetamiprid

Clothianidin

Dinotefuran

Imidacloprid

Thiamethoxam

 

4C

 

Sulfoxaflor

Sulfoxaflor

5

Nicotinic acetylcholine receptor allosteric activators

Spinosyns

Spinetoram

Spinosad

6

Chloride channel activators

Avermectins,

Milbemycins

Abamectin

Emamectin benzoate

Milbemectin

7

7A

Juvenile hormone mimics

Juvenile hormone analogues

Hydroprene

Kinoprene

Methoprene

 

7B

 

Fenoxycarb

Fenoxycarb

7C

Pyriproxyfen

Pyriproxyfen

8

8A

Miscellaneous non-specific (multi-site) inhibitors

Alkyl halides

Methyl bromide and other alkyl halides

 

8B

 

Chloropicrin

Chloropicrin

 

8C

 

Sulfuryl fluoride

Sulfuryl fluoride

8D

Borax

Borax

9

9B

Modulators of chordotonal organs

Pymetrozine

Pymetrozine

9C

Flonicamid

Flonicamid

10

10A

Mite growth inhibitors

Clofentezine

Hexythiazox

Clofentezine

Hexythiazox

 

10B

 

Etoxazole

Etoxazole

11

Microbial disruptors of insect midgut membranes (includes transgenic crops expressing B.t. toxins)

Bacillus thuringiensis or Bacillus sphaericus and the insecticidal proteins they produce

Bacillus thuringiensis subsp. israelensis

Bacillus sphaericus

Bacillus thuringiensis subsp. Kurstaki

Bacillus thuringiensis subsp. aizawai

Bt crop proteins

12

12B

Inhibitors of mitochondrial ATP synthase

Organotin miticides

Fentutatin oxide

 

12C

 

Propargite

Propargite

13

Uncouplers of oxidative phosphorylation via disruption of the proton gradient

Chlorfenapyr

Chlorfenapyr

15

Inhibitors of chitin biosynthesis, type 0, Leptdopteran

Benzoylureas

Diflubenzuron

Hexaflumuron

Lufenuron

Novaluron

Noviflumuron

16

Inhibitors of chitin biosynthesis, type 1

Buprofezin

Buprofezin

17

Molting disruptor, Dipteran

Cyromazine

Cyromazine

18

Ecdysone receptor agonists

Diacylhydrazines

Halofenozide

Methoxyfenozide

Tebufenozide

19

Octopamine receptor agonists

Amitraz

Amitraz

20*

20A

Mitochondrial complex III electron transport inhibitors

Hydramethylnon

Hydramethylnon

20B

Acequinocyl

Acequinocyl

21*

21A

METI acaricides and insecticides

Fenazaquin

Fenazaquin

Fenpyroximate

Pyridaben

Tolfenpyrad

21B

Mitochondrial complex I electron transport inhibitors

Rotenone

Rotenone

22*

22A

Voltage-dependent sodium channel blockers

Indoxacarb

Indoxacarb

22B

Metaflumizone

Metaflumizone

23

 

Inhibitors of acetyl CoA carboxylase

Tetronic and tetramic acid derivatives

Spirodiclofen

Spiromesifen

Spirotetramat

24

24A

Mitochondrial complex IV electron transport inhibitors

Phosphine

Aluminum phosphide

Phosphine

Zinc phosphide

28

Ryanodine receptor modulators

Diamides

Chlorantraniliprole

Cyantraniliprole

Flubendiamide

UN

Compounds of unknown or uncertain mode of action@

Azadirachtin

Azadirachtin

Bifenazate

Bifenazate

Cryolite

Cryolite

Dicofol

Dicofol

Pyridalyl

Pyridalyl

*Groups and Sub-groups: Although sharing the same primary target site, it is possible that not all members of a single mode of action class have been shown to be cross-resistant. Different resistance mechanisms that are not linked to the target site, such as enhanced metabolism, may be common for such a group of chemicals. In such cases, the mode of action grouping is further divided into sub-groups.

@A compound with an unknown or controversial mode of action or an unknown mode of toxicity will be held in category UN until evidence becomes available to enable that compound to be assigned to a more appropriate mode of action class.

Footnotes

1.

This document is PI-83, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date October 2005. Revised April 2014. Reviewed April 2014. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Frederick M. Fishel, professor, Agronomy Department, and director, Pesticide Information Office; UF/IFAS Extension, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. Use pesticides safely. Read and follow directions on the manufacturer's label.


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U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.