Classification of herbicides

classification of herbicides

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

2. 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

3. 1.Based on mode of action A.Contact herbicide: These herbicide Are being less mobility,kills the plant primarIly be contact with the plant tissue e.g.paraquat, diquat, propanil, oxyflurfenac . B.Systemic or translocated Herbicides: Herbicide moves within the plant from the point of treatment to its other part to variable extent e.g. all herbicide except contact are systemic in nature like 2,4-D, atrazin, pendimethalin, glyphosate, metribuzin etc. Atrazine is systemic and contact herbicide

4. 2.Based on time of application A.Pre plant incorporation (PPI): Application of herbicide in finally prepared levelled soil one day or just before sowing of a crop. These herbicides usually have higher vapour pressure or volatile nature.e.g. Fluchloraline, EPTC, trifluralin. B.Pre emergency: Application of Herbicide 1-2 days after sowing or immediately after showing of a crop but before the emergence of crop but before germination of crop.e.g. Pendimethalin, Atrazine, alachlor, butachlor,metribuzine. C.Post emergencemergence: Application of after the emergence of crop and weeds both (generally 15-30 days after sowing).e.g. 2,4-D, isoproturon, sulfosulfuron, metsulfuron, clodinafop-propargyl etc.

5. 3. Based on selectivity A.Selective herbicide: Herbicide which kills selectivity a particular group of weeds in a mixed stands of plants. e.g. all the pre emergence and post emergence applied herbicides of field crops. B. Non Selective herbicide: Herbicide which kills any species of plant irrespective of weeds and crop. They are used in controlling weed in road sides and non cropped area. e.g. paraquat, diquat, glyphosate, glyphosinate, acrolein, picroram, amitrol etc.

6. 4.Based on Spectrum of weed control A. Narrow spectrum Herbicide: Herbicide which control particular group of weeds and due to their narrow range usually do not control even all the weeds of particular group. e.g. 2,4-D (kills only broad leaved weeds and sedges, not grasses)., metsulfuron-methyl etc. B. Broad spectrum herbicide: Herbicide which control wide range of weeds (grasses, broadleaved, sedges). e.g. atrazine, pendimethalin, imezathyper, alachlor, butachlor

7. 5. Based on site of application A.Soil applied/ soil active herbicides: Applied to soil or active through soil and kill germinative weeds and their parts. e.g. all pre plant incorporation and pre emergence herbicides are include in this category. B. Foliar applied: Applied to foliage of plant or non cropped weeds.e.g. all post emergence herbicides (2,4-D, isoproturon, sulfosulfuron, metribuzin etc.) + non cropped herbicides (paraquat, glyphosate etc.) C. Both soil and foliage active herbicides: Atrazine, metribuzin in have both action.

8. 6. Based on residual action in soil: A.Non residual/ Zero persistence herbicide: These herbicides easily degraded or metabolised after application and leaves no or less residues in applied soil.e.g. paraquat, diquat, glyphosate these are used in zero/ minimum tillage) B.Residual herbicide: Herbicide which are more resistant to degradation and maintain their effect in soil for a relatively short period (usually 15-16 weeks) e.g. Triazines & Phenyl ureas.

9. 7. Based on chemical structure A.Inorganic Herbicides: Contain no carbon actions in their molecules. These were the first chemicals used for weed control before the introduction of the organic compounds, example are: 1)Acids: Arsenic acid, arsenious acid, arsenic trioxide sulphuric acid. b) Salts: Borax, copper sulphate, ammonium sulphate, Na chlorate , Na arsenite , copper nitrate. B.Organic Herbicides: a) Oils: Diesel oil, standard solvent, xylene-type, aromatic oils, polycyclic , aromatic oils etc. b) Aliphatics: Dalapon, TCA, Acrolein, Glyphosphate methyl bromide. c) Amides: Propanil, butachlor, alachlor, CDAA, Diphenamide, Naptalam, Propachlor.

10. 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 ( Toluidines) : 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, norea siduson, metoxuron.

11. N) Uracils: Bromacil, terbacil, lenacil . O) Diphenyl Ethers: Nitrogen, flurodifen . P) Organic Arsenicals: Cacodlic acid, MSMA, DSMA. Q) Others: Bentazon, Piclaram, Pyrazon, Pyrichlor, endothall, bensulphioe, MH, DCPA.

12. 8.Based on formulations A.Wettable powders: When the herbicide materials are of low solubility in water, they can be grounded into fine powder for suspension in water. This type of formulations are called wettable powders (wp).e.g. Simaidiallateraine, 2,4-D, Sodium Salt, Diuron, Linuron B. Liquid water soluble(concentrates): Herbicide formulations which are in the form of soluble liquids are called water soluble concentrates(WSC).E.g. 2,4-D, amine, dicamba, diquat, paraquat. C. Emulsifiable concentrate: The active ingredient is dissolved in solvent and an emulsifier is added to it. Since the emulsifier helps in uniform distribution of the chemical in water, no stirring is necessary while spraying.e.g. 2,4-D ester, alachlor, nitrofin, diallate.

13. D. Liquid suspension: If the active ingredient is not soluble in water, it is solubilized in organic solvents. When the product of active ingredient and solvent is added to water forspraying, it forms a liquid suspension.e.g. Atrazine, cyprazine, nitralin. E. Soluble powders: These herbicide formulations are water soluble powders (SP). They form a homogeneous solution when dissolved in water which can be applied by spraying. Salts of most herbicides are soluble in water.e.g. Sodium salt of 2,4-D, TCA, endothal, dalapan etc F. Granules: Small pellets or granules are made with inert clays. The solution of the toxicant is sprayed on these granules in desired quantity and dried. The granules are then packed for subsequent use.e.g. granules of butachlor, 2,4-D.

14. 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)

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