Draft:HRAC classification

• Comment: The article is titled "herbicide resistance classification" but mostly describes mechanisms of pesticide action, which are summarized in a more reader-friendly way on our Pesticide article. The terminology isn't used at all in the table either making it unclear what is being conveyed. Reconrabbit 15:56, 20 September 2024 (UTC)

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The Herbicide Resistance Action Committee, (HRAC), classifies herbicides by their mode of action, to help farmers and growers manage pesticide resistance. The HRAC's classification system is intended to provide a fast overview of a herbicide's mode of action. It is run by CropLife International in conjunction with the Weed Science Society of America, (WSSA).

Resistance Overview

A weed that develops resistance to one herbicide also resists any other herbicides with the same mode of action (MoA), so herbicides with different MoAs, or different resistance groups, are needed. Preventative weed resistance management rotates herbicide types to prevent selective breeding of resistance to the same mode of action. By rotating MoAs, successive generations gain no advantage from any resistant mutations of the last generation. Cross-resistant and multiply resistant weeds resist multiple MoAs, and are particularly difficult to control.

Organisation

The HRAC is a global organisation with regional organisations for the United States, Australia, Europe, South Africa, Asia, Japan, Brazil and Argentina. The WSSA works closely with the US-HRAC.

Naming Types

The HRAC give a letter based class to each active constituent herbicide. The Australian HRAC code is separate, though often the same, as the global code. In 2021, numeric classes were added, to make codes globally more consistent, add or move a few herbicides that had been misclassified, and due to concerns that using the alphabet would be difficult for international growers.

Groups

HRAC Classification Groups

HRAC (AUS)	HRAC (Global)	HRAC (Numeric)	Mode of action	Example herbicides	Example chemical families
A	A	1	Inhibits acetyl coa carboxylase	Haloxyfop-methyl, Clethodim, Sethoxydim, Pinoxaden	Aryloxyphenoxy-propionates, Cyclohexanediones, Phenylpyrazolines
B	B	2	Inhibits acetolactate synthase	Imazamox, Chlorsulfuron, Pyrithiobac-sodium, Florasulam	Imidazolinones, Pyrimidinyl benzoates, Sulfonylureas, Triazolopyrimidines
C	C1 / C2	5	Inhibits photosynthesis at PSII - serine 264 binders	Atrazine, Simazine, Propanil, Amicarbazone, Bromacil, Diuron	Triazines, Amides, Phenlcarbamates, Pyridazinones, Triazinones, Triazolinones, Uracil, Ureas
C	C3	6	Inhibits photosynthesis at PSII - histidine 215 binders/uncouplers	Bentazon, Bromoxynil, Ioxynil	Benzothiadiazinones, Nitriles
-	C2	7		Isoproturon	Urea
D	K1	3	inhibits microtubule assembly	Trifluralin, Pendimethalin, Propyzamide, Dithiopyr, butamiphos, chlorthal-dimethyl	Dinitroanilines, Benzoic acids, Pyridines, Phosphoroamidates, Benzoic acids
E	K2	23	Inhibits microtubule organisation	Carbetamide	Carbamates
F	F1	12	Inhibits phytoene desaturase	Diflufenican, Norflurazon	Phenyl ethers, N-Phenyl heterocycles
G	E	14	Inhibits protoporphyrinogen oxidase	Butafenacil, Carfentrazone-ethyl, Oxyfluorfen	N-Phenyl-imides. Diphenyl ethers, N-Phenyl-oxadiazolones, Phenylpyrazoles
H	F2	27	Inhibits hydroxyphenyl pyruvate dioxygenase	Isoxaflutole, Pyrasulfotole, Mesotrione	Ssoxazoles, Pyrazoles, Triketones
I	O	4	Auxin mimic	Dicamba, Halauxifen, Picloram, 2,4-D, MCPA, Triclopyr, Quinclorac	6-Arylpicolinates, 6-Chloropicolinates, Benzoates, Phenoxy-carboxylates, Pyridyloxy-carboxylates, Quinoline-carboxylates
J	K3 / N	15	Inhibits very long chain fatty acid synthesis	Prosulfocarb, Ethofumesate	Thiocarbamates, Benzofurans
J		-	Unknown	Bensulide, Delapon	Chlorocarbonic acids
K	K3	15	Inhibits very long chain fatty acid synthesis	Metolachlor, Pyroxasulfone	α-Chloroacetamides, Isoxazolines
K		-	Unknown	Napropamide	Acetamide
L	D	22	PS I electron diversion	Diquat, Paraquat	Pyridinium
M	G	9	Inhibits enolpyruvil shikimate phosphate synthase	Glyphosate	Glycine
N	H	10	Inhibits glutamine-synthetase	Glufosinate-ammonium	Phosphinic acid
O	L	29	inhibition of cellulose synthesis	Isoxaben, Dichlobenil, Indaziflam	Nitrile, Benzamide, Alkylazine
P	P	19	Auxin transport inhibitor	Naptalam	Aryl-carboxylates
Q	F3 / F4	13	Inhibits deoxy-d-xylulose phosphate synthesis	Clomazone, Bixlozone	Isoxazolidinone
Q	-	-	Unknown	Amitrole	Triazole
R	I	18	Inhibits dihydropteroate synthase	Asulam	carbamate
-	-	28	Inhibition of dihydroorotate dehydrogenase	Tetflupyrolimet
T	Q / Z	30	Inhibits fatty acid thioesterase	Cynmethylin	Benzyl-ether
Z	R	31	Inhibits serine-threonine protein phosphatase	Endothal	Other
Z	Z	-	Unknown	Flamprop-m, DSMA, MSMA, Pelargonic acid	Arylaminopropionic acid, Others
-	M	24	Uncouplers	Dinosam	Dinitrophenol
-	S / F3	32	Inhibition of Solanesyl Diphosphate Synthase	Aclonifen	Diphenyl ether
-	T	33	Inhibition of Homogentisate Solanesyltransferase	Cyclopyrimorate	Phenoxypyridazine

Some herbicides are doubly classified, for example, Quinmerac which is doubly classified as Group 4/29, or O/L, acting through both modes.