This document classifies herbicides in several ways: 1. By mode of action - including contact, systemic, and those that are both contact and systemic. 2. By time of application - including pre-plant incorporation, pre-emergence, and post-emergence. 3. By selectivity - selective herbicides kill particular weeds while non-selective herbicides kill any plant species. 4. Additional classifications include spectrum of weed control, site of application, residual action in soil, chemical structure, and formulation. Common herbicides are provided as examples for each classification.

1. Rajmata Vijayaraje Scindia krishi Vishwavidyalaya
Gwalior
College of Agriculture, Gwalior
Submitted To-
Dr.Varsha Gupta
Dept. of Agronomy.
Submitted by-
Vandana Dhurve
Roll no.20111112
M.Sc. Previous
Dept. of Agronomy
Subject: Principles & Practices of Weed management
Assignment on Herbicide Classification

3. Classification of Herbicides
▶ Classification can be based on-
A. Based on Mode of action
B. Based on time of application
C. Based on selectivity
D. Based on spectrum of weed control
E. Based on site of application
F. Based on residual action in soil
G. Based on chemical structure
H. Based on formulation

4. 1.Basedonmodeofaction
A.Contact herbicide:
TheseherbicideArebeinglessmobility,killstheplantprimarIlybecontactwiththe
planttissue e.g.paraquat,diquat,propanil,oxyflurfenac.
B.SystemicortranslocatedHerbicides:
Herbicidemoveswithintheplantfromthepointoftreatmenttoitsotherpart to
variable extente.g.all herbicideexcept contactaresystemic innaturelike2,4-D,
atrazin,pendimethalin,glyphosate, metribuzinetc.Atrazineis systemic andcontact
herbicide

5. 2.Basedontimeofapplication
A.Pre plantincorporation(PPI):Applicationofherbicideinfinallyprepared levelledsoilone day
orjust beforesowingofacrop.Theseherbicidesusuallyhavehighervapourpressure orvolatile
nature.e.g. Fluchloraline,EPTC,trifluralin.
B.Preemergency:
ApplicationofHerbicide1-2 days aftersowingorimmediatelyaftershowingofacropbutbefore
theemergenceofcropbutbeforegerminationofcrop.e.g.Pendimethalin,Atrazine, alachlor,
butachlor,metribuzine.
C.Post emergencemergence:
Applicationofaftertheemergenceofcropandweedsboth(generally15-30daysafter
sowing).e.g.2,4-D, isoproturon,sulfosulfuron, metsulfuron,clodinafop-propargyletc.

6. 3. Basedonselectivity
A.Selectiveherbicide:
Herbicidewhichkills selectivityaparticular groupofweedsinamixedstandsofplants.
e.g.all thepreemergence andpostemergence appliedherbicidesoffieldcrops.
B.NonSelectiveherbicide:
Herbicidewhichkillsanyspecies ofplantirrespectiveofweedsandcrop.Theyareusedin
controllingweedinroadsidesandnoncroppedarea.
e.g. paraquat,diquat,glyphosate, glyphosinate,acrolein, picroram,amitrol etc.

7. 4.BasedonSpectrumofweedcontrol
A.NarrowspectrumHerbicide:
Herbicidewhichcontrolparticular groupofweedsandduetotheir narrowrangeusuallydo
notcontrolevenall theweedsofparticulargroup.
e.g.2,4-D(kills onlybroadleavedweedsandsedges, notgrasses)., metsulfuron-methyl etc.
B.Broadspectrumherbicide:
Herbicidewhichcontrolwiderangeofweeds(grasses, broadleaved, sedges).
e.g.atrazine, pendimethalin,imezathyper, alachlor,butachlor

8. 5. Basedonsiteofapplication
A.Soil applied/ soil activeherbicides:
Appliedtosoiloractive throughsoil andkill germinativeweedsandtheir parts. e.g.all pre
plantincorporationandpreemergence herbicidesareincludeinthiscategory.
B. Foliarapplied:
Appliedtofoliageofplantornoncroppedweeds.e.g.allpostemergenceherbicides(2,4-D,
isoproturon,sulfosulfuron,metribuzinetc.)+noncroppedherbicides(paraquat,glyphosate
etc.)
C. Bothsoil andfoliageactiveherbicides:
Atrazine, metribuzininhavebothaction.

9. 6. Basedonresidualactioninsoil:
A.Nonresidual/ Zeropersistenceherbicide:
Theseherbicideseasilydegradedormetabolisedafterapplicationandleavesnoorless
residues inappliedsoil.e.g.paraquat,diquat,glyphosate theseareusedinzero/ minimum
tillage)
B.Residual herbicide:
Herbicidewhicharemoreresistanttodegradationandmaintaintheireffect insoil fora
relativelyshort period(usually15-16weeks)
e.g. T
riazines&Phenyl ureas.

10. 7. Basedonchemical structure
A.InorganicHerbicides:
Containnocarbonactionsintheir molecules.Thesewerethefirst chemicalsusedforweed
controlbeforetheintroductionoftheorganiccompounds,exampleare:
1)Acids:Arsenic acid, arsenious acid,arsenic trioxide sulphuricacid.
b)Salts:Borax, coppersulphate,ammoniumsulphate,Nachlorate, Naarsenite, coppernitrate.
B.OrganicHerbicides:
a) Oils:Diesel oil, standardsolvent, xylene-type, aromaticoils, polycyclic , aromaticoilsetc.
b)Aliphatics:Dalapon, TCA,Acrolein, Glyphosphatemethyl bromide.
c)Amides:Propanil, butachlor,alachlor,CDAA,Diphenamide,Naptalam, Propachlor.

11. d) Benzoics:2,3,6 TBA,Diacamba, tricamba,chloramben, Fenac.
e) Bipyridyliums:Paraquat , diquat.
f) Carbamates:Propham, chloropham, barban.
g)Thocarbamates:Butylate, dilate, triallate, EPTC,molinate, pebulate, vernolate, benthlocarb, aslum,
cycolate.
h) Dithiocarbamates:CDEC , Metham.
i) Nitralin ( Benzonitrates):Dichlobenil , bromoxynil, ioxynil.
j)Ditroanilines (T
oluidines) :Benefin, nitralin, trifluralin, butralin, dinitramine, fluchlorine, oxyzalin,
penoxalin.
k) Phenoxy:2,4-D, 2,4, 5-T
, MCPB,2,4-DB, 2,4- DP
, 2,4, 5-TP(silvex)
L) Triazines:Atrazine, simazine,ametryne, terbuteryne, cyprazinc, Metribuzin,prometryn
M)Ureas:Monuron,diuron,fenuron,neburon,flumeturon,mothabenzathiazuron- buturon,
chlorbromuron,chloroxuron,noreasiduson,metoxuron.

12. N)Uracils:Bromacil, terbacil, lenacil.
O)Diphenyl Ethers:Nitrogen,flurodifen.
P) OrganicArsenicals:Cacodlic acid, MSMA, DSMA.
Q)Others:Bentazon,Piclaram, Pyrazon, Pyrichlor, endothall, bensulphioe, MH,DCP
A.

13. 8.Basedonformulations
A.W
ettablepowders:
Whentheherbicidematerialsareoflowsolubilityinwater,theycanbegroundedintofinepowder
forsuspensioninwater.Thistypeofformulationsarecalled wettablepowders(wp).e.g.
Simaidiallateraine, 2,4-D,SodiumSalt, Diuron,Linuron
B. Liquidwatersoluble(concentrates):
Herbicideformulationswhichareintheformofsolubleliquidsarecalled watersoluble
concentrates(WSC).E.g.2,4-D, amine,dicamba,diquat,paraquat.
C. Emulsifiableconcentrate:
Theactive ingredient is dissolved in solvent andan emulsifier is addedto it. Since the emulsifier
helpsin uniform distribution of the chemicalin water, nostirring is necessarywhile spraying.e.g.
2,4-Dester,alachlor,nitrofin,diallate.

14. D.Liquidsuspension:
If theactive ingredientisnotsolubleinwater,it issolubilized inorganicsolvents. Whenthe
productofactive ingredientandsolventisaddedtowaterforspraying, it formsaliquid
suspension.e.g.Atrazine, cyprazine, nitralin.
E. Solublepowders:
Theseherbicide formulations arewater soluble powders(SP). Theyformahomogeneoussolution
whendissolvedin waterwhichcanbeappliedbyspraying. Salts of mostherbicidesare solublein
water.e.g.Sodiumsalt of2,4-D, TCA,endothal,dalapanetc
F.Granules:
Smallpellets orgranulesaremadewithinertclays. Thesolutionofthetoxicant issprayedon
thesegranulesindesiredquantityanddried. Thegranulesarethenpackedforsubsequent
use.e.g.granulesofbutachlor, 2,4-D.

15. Reference- Principles of crop production (S.R.Reddy), Principles of Agronomy
(Reddy & Reddy), Competitive book of Agriculture (Nem Raj Sunda), Research
paper of KVK Rewa(JNKVV)

16. Thankyou