Herbicide Modes of Action (effect on plant growth) This chart groups herbicides by their modes of action to assist you in selecting herbicides 1) to maintain greater diversity in herbicide use and 2) to rotate among herbicides with different sites of action to delay the development of herbicide resistance. Site of Action Group* Site of Action Species in U.S. No. of Resistant Weed Chemical Family Active Ingredient Site of Action Group* Site of Action Species in U.S. No. of Resistant Weed Chemical Family Active Ingredient ACCase 15 Aryloxyphenoxy fenoxaprop 10 Glutamine 0 None accepted glufosinate 1 Inhibitors propionate fluazifop Synthesis (acetyle CoA quizalofop Inhibitor carboxylase) Nitrogen Metabolism Inhibitors Cyclohexanedione clethodim Lipid Synthesis sethoxydim 13 Diterpene 0 Isoxazolidinone clomazone Synthesis 2 ALS Inhibitors 38 Sulfonylurea chlorimuron Inhibitor (acetolactate foramsulfuron HPPD 0 Isoxazole isoxaflutole synthase) halosulfuron 27 Inhibitors iodosulfuron Triketone mesotrione nicosulfuron tembotrione primisulfuron Pigment Inhibitors tropramezone prosulfuron rimsulfuron 14 PPO 2 Diphenylether acifluorfen, thifensulfuron Inhibitors fomesafen tribenuron lactofen N-phenylphthalimide flumiclorac Imidazolione imazamox flumioxazin imazaquin imazethapyr Aryl triazinone sulfentrazone carfentrazone Triazoloyriidine flumetsulam Trifluoromethyl saflufenacil Amino Acid Synthesis Inhibitors cloransulam uracils EPSP Synthase 7 None accepted glyphosate Photosystem I 4 Bipyridilium paraquat 9 Cell Membrane Disrupters 22 Inhibitor Electron (5-enolpyruvyl-shikimate-3-phosphate Diverter 4 Specific site 7 Phenoxy 2,4-D 3 Microtubule 6 Dinitroaniline ethalfluralin unknown Inhibitors pendimethalin Benzoic acid dicamba trifluralin Carboxylic acid clopyralid Growth Seedling Root Regulators fluroxypyr Growth Inhibitors (Synthetic auxins) 19 Auxin 0 Semicarbazone diflufenzopyr Transport 8 Lipid 5 Thiocarbamate butalate Synthesis EPTC 5 Photosystem II 22 Triazine atrazine Inhibitors Inhibitors simazine (not ACCase) (different binding Triazinone metribuzin than 6 & 7) 15 Long-chain 1 Chloroacetamide acetochlor Fatty Acid alachlor 6 Photosystem II 1 Nitrile bromoxynil Inhibitors Inhibitor metachlor Inhibitors dimethenamid (different binding Benzothiadiazole bentazon than 5 & 7) Oxazolinone pyroxasulfone 7 Photosystem II 7 Ureas linuron Seedling Shoot Growth Inhibitors Oxyacetamide flufenacet Photosynthesis Inhibitors (different binding *Site of Action Group is a classification system developed by the Weed than 5 & 6) Scienc e Society of America. This table is excerpted with permission from the Corn and Soybean Herbicide Chart (GWC-3), part of the Glyphosate, Weeds, and Crop Series published by Purdue University through a cooperative effort of weed scientists in the 16-state USDA North Central Region. Contained here are pages 8-10 of the 2016 Guide for Weed, Disease, and Insect Management in Nebraska. The 300+ page guide is available at Marketplace.unl.edu 8 © The Board of Regents of the University of Nebraska–Lincoln. All rights reserved. Classification of Herbicides by Herbicide Classification Mode and Site of Action and Chemical Family Herbicides may be classified into of herbicide-resistant weeds or problems These problems can be lessened by rotating families based on how they kill plants with chemical carryover. or combining herbicides with different (mode of action and site of action) or Repeated use of a herbicide or herbicides action sites. In the table the site of herbicide by chemical similarity. An example of a with the same site of action may lead to uptake is indicated by: R = root uptake; S = common commercial herbicide containing selection of herbicide-resistant weeds, shoot uptake; and F = foliage uptake. Letter the active ingredient is also listed. Please or a shift in the weed species present in sequence indicates the primary order of refer to the Herbicide Dictionary to identify the field to weeds tolerant to a particular herbicide uptake. Repeated use of herbicides other commercial herbicides that contain herbicide or herbicide family. For example, with a common mode and site of action pose the same active ingredient. In some cases, repeated use of ALS inhibitors can result the highest risk of an additive effect which herbicides from different chemical families in the selection for ALS-resistant weeds. can lead to resistant weed development, have a similar site of action. A knowledge of Using both sulfonylurea and imidazolinone additional carryover, or more crop injury. herbicide families and herbicide mode and herbicides (Classic, Pursuit, etc.) in the same Refer to the journal, Weed Technology, 11: site of action will reduce the risk of choosing growing season can result in increased 384-393 (1997) for additional information on herbicides that will lead to the development carryover problems or possible crop injury. herbicide classification. Common Name — Trade Name — Site of Uptake Lipid Synthesis Inhibition 3. Triazolopyrimidine Group 1. ACCase inhibition chloransulam methyl — FirstRate — F/R 1. Aryloxyphenoxypropionates (FOPs) florasulam — R/F clodinafop propargyl — Discovery — F flumetsulam — Python — R/F diclofop — Hoelon — F pyroxsulam — PowerFlex — F/R fenoxaprop — Acclaim Extra — F 4. Pyrimidinyloxybenzoic acid fluazifop-P — Fusilade DX — F bispyribac-sodium — Velocity — F pinoxaden — Axial — F 5. Triazolones quizalofop-P — Assure II — F flucarbazone — Everest — F/R 2. Cyclohexanediones (DIMs) propoxycarbazone-sodium — Olympus — F/R clethodim — Select Max — F thiencarbazone-methyl — Corvus — F/R sethoxydim — Poast — F Group 9. EPSP synthetase inhibition tralkoxydim — Achieve — F glyphosate — Roundup/Touchdown — F Amino Acid Synthesis Inhibition Seedling Growth Inhibition Group 2. ALS-AHAS inhibition Group 3. Microtubule assembly inhibition 1. Imidazolinones 1. Dinitroanilines imazamethabenz — Assert — R/F benfluralin — Balan — S/R imazamox — Raptor — F/R ethalfluralin — Curbit/Sonalan — S imazapic — Plateau — R/F oryzalin — Surflan — S imazapyr — Arsenal — R/F pendimethalin — Prowl — S imazaquin — Scepter — R/F prodiamine — Barricade — S imazethapyr — Pursuit — R/F trifluralin — reflan—ST 2. Sulfonylureas 2. Pyridines bensulfuron — Londax — F/R dithiopyr — Dimension — R/F chlorimuron — Classic — F/R 3. Benzamides chlorsulfuron — Glean/Telar — F/R pronamide — Kerb — S/R ethametsulfuron — Muster — F 4. Benzoic acids foramsulfuron — Option—F DCPA — Dacthal — R halosulfuron — Permit — F/R Group 15. Long-chain fatty acid inhibitor iodosulfuron — Autumn — F 1. Chloroacetamides metsulfuron — Ally/Escort — F/R acetochlor — Harness/Surpass NXT — S/R nicosulfuron — Accent — F alachlor — Intrro — S/R primisulfuron — Beacon — F/R dimethenamid — Outlook — S/R prosulfuron — Peak — F/R metolachlor — Dual — S/R rimsulfuron — Matrix — F/R propachlor — Ramrod — S/R sulfometuron — Oust — F/R 2. Oxyacetamides sulfosulfuron — Maverick flufenacet — Define — S/R thifensulfuron — Harmony — F/R 3. Acetamides triasulfuron — Amber — F/R napropamide — Devrinol — R/S tribenuron — Express — F/R 4. Oxazoles triflusulfuron — Upbeet — F pyroxasulfone — Zidua — S/R © The Board of Regents of the University of Nebraska–Lincoln. All rights reserved. 9 Seedling Growth Inhibition (continued) Group 16. Lipid synthesis inhibition (not ACCase) Group 6. C3 class 1. Benzofuranes 1. Benzothiadiazinones ethofumesate — Nortron SC — S/R bentazon — Basagran — F Group 8. 1. Phosphorodithionates 2. Nitriles bensulide — Betasan — R bromoxynil — Buctril—F 2. Thiocarbamates 3. Phenylpyridazine butylate — Sutan + — S/R pyridate — Tough — F cycloate — Ro-Neet — S/R Cell Membrane Disruption EPTC — Eradicane — S/R Group 14. PPO inhibition triallate — Far-Go — S/R 1. Diphenylethers Group 19. Auxin transport inhibition acifluorfen — Blazer — F 1. Phthalamates fomesafen — Reflex/Flexstar — R/F naptalam — Alanap — R/F lactofen — Phoenix/Cobra — F 2. Semicarbazone oxyflurofen — Goal — R/S diflufenzopyr — Distinct — F 2. N-phenylphthalimides Cell Wall Synthesis Inhibition flumiclorac — Resource — F Group 21. Benzamides flumioxazin — Valor — S/F isoxaben — Gallery — R/S 3. Triazinones Group 20. Nitriles sulfentrazone — Authority/Spartan — R dichlobenil — Casoron — R/F carfentrazone ethyl — Aim — F Growth Regulators 4. Thiadiazoles Group 4. Synthetic auxins fluthiacet methyl — Cadet — F 1. Phenoxyacetic acids 5. Phenylpyrazoles 2,4-D — many — F/R pyraflufen-ethyl — Vida — F 2,4-DB — Butyrac — F 6. Trifluoromethyl uracils dichlorprop — many — F saflufenacil — Kixor — R/F/S MCPA — many — F/R Group 22. Photosystem I electron diversion mecoprop — many — F 1. Bipyridyliums 2. Benzoic acids diquat — Reward — F dicamba — Banvel/Clarity — F/R/S paraquat — Gramoxone — F 3. Pyridine carboxylic acids Unclassified Cellular pH alteration aminopyralid — Milestone — F/R 1. Fatty acids clopyralid — Stinger — F/R pelargonic acid — Scythe — F fluroxypyr — Starane — F Carotenoid Biosynthesis Inhibition (Pigment Inhibitors) picloram — Tordon — F/R Group 12. Phytolene desaturase inhibition triclopyr — Garlon — F/R 1. none accepted 4. Quinoline carboxylic acids fluridone — Avast — S/R quinclorac — Paramount — F/S 2. pyridazinone 5. Pyrimidine carboxylic acids norflurazon — Zorial — S aminocylopyrachlor — Imprelis — F/R Group 27. 4-HPPD inhibition Photosynthesis Inhibition (Photosystem II) — Classes differ in 1. Callistemones binding behavior mesotrione — Callisto — F/R tembotrione — Laudis — F/R Group 5. C1 class 1. Triazines 2. Isoxazoles ametryn — Evik — R/F isoxaflutole — Balance