HERBICIDE RESISTANCE/SOA

Transcription

1 HERBICIDE RESISTANCE AND SITE OF ACTION MANAGING THE PROBLEM Through the repeated use of herbicides with similar modes of action, on the same site, we have imposed selection for increased resistance within existing weed populations. The result is the development of species or biotypes that can no longer be controlled with some selective herbicides. There has been a dramatic increase in the incidence of herbicide resistance over the last 20 years. There are currently over 310 weed biotypes where herbicide-resistant biotypes have been reported. Triazine and ALS inhibiting herbicides account for most of the examples of resistance. Weed resistance to the sulfonylurea and imidazolinone herbicides developed after a few years of use. Like triazine-resistant biotypes, the resistant biotypes show varying degrees of cross resistance to other chemicals in the same chemical family. Multiple resistance to several different classes of herbicides has also become a major concern. Sulfonylurea, sulfonamide and imidazolinone herbicides have the same mode of action. They inhibit the action of the ALS enzyme needed for the production of essential amino acids required for cell development in plants. The potential to develop weed resistance to these herbicides is high where an ALS-inhibiting herbicide is used in more than one crop in a 2 or 3 year crop rotation, e.g., corn-soybean rotations. Using crops resistant to ALSinhibiting herbicides increases the continued use of herbicides with the same mode of action. With the annual rate of introduction of new pesticides rapidly declining, it is imperative that we avoid losing safe and effective products due to misuse that builds up resistance to weed population. This is especially important in the new ALS-inhibiting herbicides that are used at lower rates and pose less environmental risk than many other pesticides. RELATIVE RISK OF DEVELOPING RESISTANCE High Risk Amino Acid Synthesis Inhibitors (ALS Inhibitors) Lipid Synthesis Inhibitors (ACCase Inhibitors) Medium Risk Photosynthesis Inhibitors (Photosystem II) Cell Membrane Disruptors (Photosystem I) Cell Membrane Disruptors (PPO Inhibitors) Pigment Inhibitors Seedling Root Inhibitors (Cell Division Inhibitors) Low Risk Amino Acid Synthesis Inhibitors (EPSPS Inhibitors) Nitrogen Metabolism Inhibitors (Glutamine Synthetase Inhibitors) Growth Regulators (Synthetic Auxin) Seedling Shoot Inhibitors RISKS ASSOCIATED WITH CERTAIN CULTURAL PRACTICES Continuous corn or soybean* Corn-soybean rotation 3-year row crop rotation Diversified rotation (small grain or alfalfa) Single SOA Single SOA Multiple SOA Multiple SOA - Cultivation + Cultivation - Cultivation + Cultivation *Chart can apply to other crops as well. Source: C. Sprague, Michigan State University CHARACTERISTICS OF HERBICIDES SUSCEPTIBLE TO WEED RESISTANCE Characteristics of herbicides and their use that contribute to an increased probability for the evolution of herbicide resistance: 1) Single site and specific mode of action; 2) Extremely effective in killing a wide range of weed species; 3) Long soil residual and season-long control of germinating weeds; 4) Applied frequently over several seasons without rotating or combining with other types of herbicides. If a herbicide-resistant weed population is identified and confirmed, it is important to determine the extent of its distribution within the immediate area. It may be possible to contain a small infestation of the species to one farm or one field. Other control measures include substituting herbicides in an existing system, altering tillage operations, the use of herbicides applied at different times during the cropping season, and crop rotation. CHARACTERISTICS OF WEED SPECIES THAT DEVELOP HERBICIDE RESISTANCE Weed species most likely to develop resistance tend to have: 1) Genetic variability; 2) A short life cycle (annuals); 3) Short seed dormancy such as kochia and Russian thistle; 4) High initial frequency of resistance in the population. ROLE OF GENETICALLY ENGINEERED CROPS IN WEED RESISTANCE MANAGEMENT Genetically engineered crops resistant to Roundup and Liberty help manage current resistant weeds and add another mode of action to prevent other weeds from developing resistance to other herbicides. However, effective weed control with these products will result in a heavy selection pressure toward any weed with natural tolerance including wild buckwheat, yellow nutsedge, velvetleaf and morningglories. The dominant weed species in a field are likely to shift to these weeds over time. Currently there are few examples of glyphosate resistance and none for Liberty or Rely 280. As a result, rapid development of weed resistance to glyphosate or Liberty does not appear to be likely. With all weed control strategies, herbicide and crop rotation should be used as a primary defense in the development of resistant weeds. STRATEGIES TO AVOID HERBICIDE RESISTANT WEEDS The fundamental principal for managing herbicide resistant weeds is to reduce selection pressure for the evolution of resistance. Perhaps the easiest and best way of accomplishing this is through mechanical control and the normal use of crop and herbicide rotation. Herbicides used in rotation should differ in their mode/site of action (see below). Simply changing the product used may not result in a change in mode/site action. Other recommendations include using shorter-residual herbicides, e.g., Ally instead of Glean XP, Raptor instead of Pursuit, tank mixes or sequential Extremely 5 High treatments of herbicides with different modes of action, e.g., tank mixing 4 High 2,4-D or Banvel/Sterling Blue/Dicamba 4E with Ally; greater integration of 3 Moderate tillage with herbicides; and preventing weed escapes from going to seed. 2 Low 1 Minimal For more information, see takeactiononweeds.com or or HERBICIDE RESISTANCE/SOA Site of Action 1 Site of Action Description 1/A ACCase inhibitor 2/B ALS/AHAS inhibitor 3/K1 Microtubule assembly inhibitor 4/0 T1R1 Auxin receptors, Synthetic auxins (growth regulators) 5/C1 Photosystem II (PSII) inhibitor Site A 6/C3 PSII inhibitor - Site B 7/C2 PSII inhibitor - Site A (different behavior than Site of Action 5) 8/N Fatty acid or lipid synthesis inhibitornon-accase Site of Action 1 Site of Action Description 9/G EPSP synthase inhibitor 10/H Glutamine synthetase inhibitor 11/F3 Bleaching - Carotenoid biosythesis inhibitor 12/F1 Bleaching - Phytoene desaturase (PDS) inhibitor 13/F3 Bleaching - DOXP inhibitor 14/E Protoporphyrinogen oxidase (PPO) inhibitor 15/K3 Cell division (VLCFA ) inhibitor - e.g. chloroacetamides Site of Action 1 Site of Action Description 17/Z Undefined - nucleic acid inhibitor; e.g. organic arsenicals (DSMA) 18/I Dihydropteroate synthase (DHP) inhibitor 19/P Auxin transport 20/L Cellulose/cell wall synthase inhibitor, Site A- nitrile 21/L Cellulose/cell wall synthesis inhibitor, Site B - benzamides 22/D Photosystem I electron diverter See table on the next two pages for herbicides and specific sites of action. 1 WSSA grouping followed by/hrac grouping. For more information on site of action, see Site of Action 1 Site of Action Description 23/K2 Mitosis/microtubule organization inhibitor 24/M Uncoupling membrane disruptors 25/Z Unknown/not classified 26/L/N/Z Quinoline carboxylic acid (L) or chlorocarbonic acids (N), or pyrazolium (Z) 27/F2 Bleaching (HPPD), PDS, other 29/L Inhibitor of cell wall synthesis, Site C 759

2 HERBICIDE SITES OF ACTION AND FAMILIES The following table is a partial list of weeds with known herbicide resistance in the United States. For full details: HERBICIDE SOA Site of Action Herbicide-Resistant Weed Species ACC-ase INHIBITOR 1/A) Giant foxtail, green foxtail, large crabgrass, Johnsongrass (Fusilade, Cleanse), persian darnel and wild oats. (grass growing point inhibitor) ALS INHIBITOR 2/B) Black nightshade, bushy wall flower/treacle mustard, cheat, cocklebur, common chickweed, common sunflower, downy brome, flix weed, giant foxtail, giant, common ragweed, green foxtail, large crabgrass, kochia, lambsquarters, marestail, palmer amaranth, prickly lettuce, prostrate, redroot and smooth pigweeds, Russian thistle, ryegrass, shattercane, waterhemp, wild mustard, wild oat, and yellow foxtail (IMI), Japanese Brome, Velvetleaf and Tansy Mustard.. CELL-MEMBRANE DISRUPTOR 14/E) Common ragweed, palmer amaranth, waterhemp. EPSP SYNTHASE INHIBITOR 9/G) Common ragweed, giant ragweed, hairy fleabane, kochia, marestail/horseweed, palmer amaranth, rigid ryegrass, waterhemp. GROWTH REGULATOR 4/O) Barnyardgrass (Facet L), kochia (dicamba), wild carrot (2,4-D), waterhemp (2,4-D). HPPD 27/F2) Waterhemp, Palmer amaranth. MICROTUBULE ASSEMBLY INHIBITOR 3/K1) (seedling root inhibitor) Annual bluegrass, goosegrass, green foxtail, Johnsongrass (trifluralin). PHOTOSYNTHESIS INHIBITOR 5/C1) Barnyardgrass, cocklebur, common lambsquarter, common ragweed, giant foxtail, jimsonweed, kochia, marestail, palmer amaranth, Pennsylvania smartweed, prostrate pigweed, smooth pigweed, velvetleaf (triazines), waterhemp, yellow foxtail. 7/C2) Barnyardgrass. Site(s) Of Action (more than one Site Mode of Action (effect on plant growth)* Site of Action Group Herbicide Family of Action indicates PREMIX) Trade Name(s) LIPID SYNTHESIS INHIBITORS ACCASE INHIBITORS 1/A Aryloxphenoxy-propionate (Fops) 1 Assure II, Clincher SF, Discover NG, Fusilade DX, Fusilade II,Illoxan 3 EC, NextStep NG, Ricestar HT, Tacoma 1EC, Targa 1,1 Foxfire, Fusion 1,2 RebelEX 1,6,27 Wolverine Advanced Cyclohexanedione (Dims) 1 Cleanse 2EC, Poast, Section Three, Select 2 EC, Select Max, Shadow, Shadow 3EC Phenylpyrazolin 1 Axial XL 1,1 Foxfire 1,4 AxialStar AMINO ACID SYNTHESIS INHIBITORS ALS INHIBITORS 2/B Imidazolinone 2 Arsenal, Arsenal PowerLine, Beyond, Cadre, Chopper Gen2, Clearcast, Habitat, Plateau, Pursuit, Raptor, Scepter, Stalker 2,14 Authority Assist, OpTill 2,14,15 Zidua PRO 2,2 Lineage Clearstand 2,2,4 Viewpoint 2,3 Pursuit Plus 2,4,26 Clearpath 2,6 Varisto 2,7 Sahara DG 2,9 Extreme, Journey, OneStep Pyrimidinyl(thio)benzoate 2 Regiment, Staple LX, Tradewind, UpBeet, Velocity SG Sulfonylaminocarbonyltriazolinone 2 Everest 2.0, Everest 3.0, Olympus, Sierra, Varro 2,2 Autumn Super 51 WDG, Rimfire Max 2,27 Capreno, Corvus 2,6,27 Huskie Complete Sulfonylurea 2 Accent Q, Ally XP, Amber Autumn, Beacon, Celero, Certainty, Classic, Envoke, Escort XP, Express, Glean XP, Harmony SG, Herbivore, League, Londax, Matrix SG, Maverick, Monument 75WG, Osprey, Oust XP, Outrider, Peak, Permit, Pre-Pare, Revolver, Sandea, Strada, Telar XP *See table on previous page for descriptions. 760

3 HERBICIDE SITES OF ACTION AND FAMILIES Site(s) Of Action (more than one Site Mode of Action (effect on plant growth)* Site of Action Group Herbicide Family of Action indicates PREMIX) Trade Name(s) AMINO ACID SYNTHESIS INHIBITORS (continued) ALS INHIBITORS (continued) 2/B Sulfonylurea (continued) 2,14 Authority Maxx, Authority XL, Blindside, Rowel FX, Valor XLT 2,14,15 Fierce XLT 2,2 Affinity BroadSpec, Affinity TankMix, Alluvex, Audit 1:1, Audit 4:1, Audit 75 WDG, Autumn Super 51 WDG, Basis Blend, Canopy EX, Cimarron Plus, Cimarron X-tra, Finesse Cereal and Fallow, Finesse Cereal and Fallow, FirstShot SG, Harmony Extra SG, Landmark XP, Leadoff, Lineage Clearstand, Oust Extra, Panoflex, Pastora, Resolve Q, Rimfire Max, Spirit, Steadfast Q, Strada Pro, Synchrony XP 2,2,14 Afforia, Enlite, Envive, Throttle XP 2,2,2 Ally Extra SG 2,2,2,4 Agility SG 2,2,4 Supremacy, Viewpoint 2,27 Butte, Instigate, Prequel, Realm Q, Revulin Q 2,4 Chaparral, NorthStar, Opensight, Perspective, Rave, Sentrallas, Streamline, Yukon 2,4,26 Strada XT2 2,4,4 Cimarron Max 2,5 Canopy Blend, Canopy, Chlorimuron, Suprend, Westar 2,5,14 Trivence 2,7 Duet 2,8 League MVP Triazolopyrimidine 2 Defendor, FirstRate GR2, Granite GR, Granite SC, Grasp SC, PowerFlex HL, Python WDG, Strongarm, TeamMate 1,2 RebelEX 2,14 Authority First, Cleantraxx, Pindar GT, Sonic, Surveil 2,2,4 GoldSky 2,4 Grasp Xtra, Hornet WDG, Orion, Quelex, Starane Flex 2,4,15 SureStart II, Threesidual, TripleFLEX II 2,4,4 PerfectMatch EPSP SYNTHASE 9/G Glycine 9 Abundit Extra, Cornerstone 5 Plus,Cornerstone Plus, Departure, INHIBITOR Duramax, Durango DMA, Rodeo, Roundup PowerMAX, Roundup PowerMAX II, Roundup Pro, Roundup Pro Concentrate, Roundup PROMAX, Roundup Ultra, Roundup WeatherMAX, RT 3, Tomahawk 4, Tomahawk 5 2,9 Extreme, Journey, OneStep 4,9 Enlist Duo, Fallow Star 9,14 Flexstar GT 3.5 9,15 Sequence 9,15,27 Halex GT 9,27 Callisto GT GROWTH REGULATORS T1R1 AUXIN 4/O Benzoic Acids 4 Banvel, Clarifier, Clarity, Dicamba Max 4, DiFlexx, Engenia, Sterling RECEPTORS - Blue, Vanquish SYNTHETIC AUXINS 2,2,2,4 Agility SG 2,4 NorthStar, Rave, Yukon 2,4,4 Cimarron Max 4,19 Distinct, Overdrive, Status 4,27 DiFlexx DUO 4,4 Brash, Brushmaster, Pulsar, Weedmaster 4,4,4 Strike 3 4,9 Fallow Star HERBICIDE SOA 761

4 HERBICIDE SITES OF ACTION AND FAMILIES HERBICIDE SOA Site(s) Of Action (more than one Site Mode of Action (effect on plant growth)* Site of Action Group Herbicide Family of Action indicates PREMIX) Trade Name(s) GROWTH REGULATORS T1R1 AUXIN 4/O Carboxylic Acid 4 Element 3A, Element 4, Elevore, Garlon 3A, Garlon 4, Garlon 4 Ultra, (continued) RECEPTORS - Grandstand, Lontrel, Method 240SL, Method 50SG, Milestone, SYNTHETIC AUXINS Pathfinder II, Reclaim, Remedy Ultra, Renovate 3, Starane Ultra, (continued) Stinger, Tordon 22K, Tordon K, Transline, Vastlan 1,4 AxialStar 2,2,4 GoldSky, Supremacy, Viewpoint 2,4 Chaparral, Grasp Xtra, Hornet WDG, Opensight, Perspective, Quelex, Sentrallas, Starane Flex, Streamline 2,4,15 SureStart II, Threesidual, TripleFLEX II 2,4,4 PerfectMatch 4,15,27 Resicore 4,4 Capstone, Confront, Crossbow, Curtail, Curtail M, Graslan L, Grazon P+D, GrazonNext HL, PasturAll, PasturAll HL, PastureGard HL, Pathway, Pulsar, Sendero, Surmount, Tordon 101 Mixture, Tordon RTU, WideMatch 4,4,4 Weld 4,4,6 Carnivore, Kochiavore 4,6 Starane NXT Phenoxy 4 2,4-D Amine 4, 2,4-D LV 4, 2,4-D LV 6, 2,4-DB 175, 2,4-DB 200, 2,4- DB DMA 175, 2,4-DB DMA 200, Butyrac 175, Butyrac 200, Enlist One, Formula 40, Hi-Dep, MCPA Amine 4, MCPA Ester 4, MCPP-p 4 Amine, Rugged, Shredder E-99, Thistrol 2,4 Orion 2,4,4 Cimarron Max 4,4 Brash, Brushmaster, Crossbow, Curtail, Curtail M, Graslan L, GrazonNext HL, Grazon P+D, PasturAll, PasturAll HL, Pathway, Tordon 101 Mixture, Tordon RTU, Weedmaster 4,4,4 Strike 3, Weld 4,4,6 Carnivore, Kochiavore 4,6 Bison 4,9 Enlist Duo Quinoline Carboxylic Acid (For dicots; also group 26/L) 4,26 Drive XLR8, Facet L (alternate SOA) 2,4,26 Clearpath, Strada XT2 4,14,26 Solitare, SquareOn AUXIN TRANSPORT INHIBITOR 19/P Semicarbazone 4,19 Distinct, Overdrive, Status PHOTOSYNTHESIS PHOTOSYSTEM II 5/C1 Phenylcarbamate 5,5 Sugarbeet Mix INHIBITORS INHIBITORS - DIFFERENT BINDING Triazine 5 Aatrex 4L, Aatrex Nine-O, Atrazine 4F, Atrazine 4L, Atrazine 90 DF, THAN 6 & 7 Atrazine 90 WDG, Caparol 4L, Cotton-Pro, Pramitol 25E, Princep 4L, Princep Caliber 90, Simazine 4L, Simazine; 90 WDG 2,5 Suprend 5,14,15 Anthem ATZ 5,15 Bicep II Magnum, Bicep Lite II Magnum, Breakfree NXT ATZ, Breakfree NXT Lite, Charger MAX ATZ, Charger MAX ATZ Lite, Cinch ATZ Cinch ATZ Lite, Confidence Xtra, Confidence Xtra 5.6L, Degree SYSTEMIC Xtra, FulTime NXT, Harness Xtra, Harness Xtra 5.6L, Keystone LA NXT, Keystone NXT, Tremor ATZ Lite NXT, Tremor ATZ NXT 5,15,27 Lexar EZ, Lumax EZ 5,15,27,27 Acuron 5,27 Callisto Xtra Triazinone 5 Dimetric EXT, Metriclude EXT, Velpar DF CU, Velpar DF VU, Velpar L, Velpar L CU, Velpar L VU 2,5 Canopy, Canopy Blend, Metribuzin, Westar 2,5,14 Trivence 5,14 Authority MTZ DF 762

5 HERBICIDE SITES OF ACTION AND FAMILIES Site(s) Of Action (more than one Site Mode of Action (effect on plant growth)* Site of Action Group Herbicide Family of Action indicates PREMIX) Trade Name(s) PHOTOSYNTHESIS PHOTOSYSTEM II 5/C1 Triazinone (continued) 5,15 Axiom DF, Boundary 6.5 EC, Presidual INHIBITORS (continued) INHIBITORS - DIFFERENT BINDING 5,7 Velpar AlfaMax, Velpar AlfaMax Gold THAN 6 & 7 (continued) Triazolinone 5 Xonerate Uracil 5 Hyvar X, Hyvar X-L, Sinbar WDG 5,7 Krovar I DF PHOTOSYSTEM II 6/C3 Benzothiadiazole 6 Basagran, Basagran 5L INHIBITORS - DIFFERENT BINDING 2,6 Varisto THAN 5 & 7 6,14 Storm Nitrile 6 Moxy 2E 1,6,27 Wolverine Advanced 2,6,27 Huskie Complete CONTACT 27,6 Talinor 4,4,6 Carnivore, Kochiavore 4,6 Bison, Starane NXT 6,27 Huskie PHOTOSYSTEM II 7/C2 Amide 7 Stam 80 EDF, Stam M4, SuperWHAM!, Vista XRT INHIBITORS - DIFFERENT BINDING 2,7 Duet THAN 5 & 6 Urea 7 Cotoran 4L, Daze 4SC, Direx 4L, Karmex DF, Linex 4L, Lorox DF, Spike 20P, Tupersan SYSTEMIC 2,7 Sahara DG 5,7 Krovar I DF, Velpar AlfaMax, Velpar AlfaMax Gold 7,7 Adios NITROGEN METABOLISM GLUTAMINE 10/H Phosphinic Acid 10 Liberty 280 SL, Rely 280 INHIBITOR SYNTHETASE INHIBITOR PIGMENT INHIBITORS BLEACHING (PDS; 12/F1 Pyridazinone 12 Solicam PHYTOENE DESATURASE) Other 12 SonarOne DITERPENE 13/F3 Isoxazolidinone 13 Command 3ME BIOSYNTHESIS INHIBITOR HPPD INHIBITORS 27/F2 Isoxazole 27 Balance Flexx, Scoparia 2,27 Corvus, Prequel Pyrazole 6,27 Huskie 1,6,27 Wolverine Advanced 2,6,27 Huskie Complete Pyrazolone 27 Armezon, Frequency, Impact, Pylex 15,27 Armezon PRO Triketone 27 Broadworks, Callisto, Incinerate, Laudis, Tenacity 14,27 Solstice 15,27 Zemax 15,27,27 Acuron Flexi 2,27 Capreno, Instigate, Realm Q, Revulin Q 27,6 Talinor 4,15,27 Resicore 4,27 DiFlexx DUO 5,15,27 Lexar EZ, Lumax EZ 5,15,27,27 Acuron 5,27 Callisto Xtra 9,15,27 Halex GT 9,27 Callisto GT Other 2,27 Butte HERBICIDE SOA 763

6 HERBICIDE SITES OF ACTION AND FAMILIES HERBICIDE SOA Site(s) Of Action (more than one Site Mode of Action (effect on plant growth)* Site of Action Group Herbicide Family of Action indicates PREMIX) Trade Name(s) CELL MEMBRANE PPO INHIBITORS 14/E Aryl triazinone 14 Aim EC, Cadet, Spartan 4F DISRUPTERS 14,14 Display, Marvel, Spartan Charge, Anthem 14,15 Anthem Flex, Anthem Maxx, Authority Elite, BroadAxe XC, Spartan Elite 14,22 Cyclone Star 14,27 Solstice 2,14 Authority Assist, Authority First, Authority Maxx, Authority XL, Blindside, Sonic 2,2,14 Throttle XP 3,14 Echelon 4SC 4,14,26 Solitare, SquareOne 5,14 Authority MTZ DF 5,14,15 Anthem ATZ Diphenylether 14 Agent 1.88, Avalanche Ultra, Cobra, Flexstar, Goal 2XL, GoalTender, Phoenix, Reflex 14,14 Marvel 14,15 Prefix, WarrantUltra 2,14 Cleantraxx, Pindar GT 6,14 Storm 9,14 Flexstar GT 3.5 N-phenylphthalimide 14 BroadStar, Clipper, Payload, Resource, Rowel, SureGuard, Valor SX 14,15 Fierce 2,14 Rowel FX, Surveil, Valor XLT 2,14,15 Fierce XLT 2,2,14 Afforia, Enlite, Envive, Trivence Oxadiazole 14 Ronstar 50 WSP, Ronstar G Phenylpyrazole 14 ET, Vida Pyrimidinedione 14 Detail, Heat, Sharpen, Treevix 2,14 OpTill 14,15 Verdict 2,14,15 Zidua PRO PHOTOSYSTEM I 22/D Bipyridylium 22 Diquat 2L, Gramoxone SL, Gramoxone SL 2.0, Reglone, Reward ELECTRON DIVERTER 14,22 Cyclone Star SEEDLING ROOT MICROTUBULE 3/K1 Benzamide 3 Kerb 50-W, Kerb SC GROWTH INHIBITORS INHIBITORS Benzoic Acid 3 Dacthal Flowable, Dacthal W-75 Dinitroaniline 3 Barricade 4FL, Barricade 65WG, Endurance, Framework 3.3EC, Pendulum 2G, Pendulum 3.3 EC, Prowl H2O, Resolute 4FL, Resolute 65WG, Sonalan 10G, Sonalan HFP, Surflan A.S., Treflan HFP, Treflan TR-10, Trust 3,8 Buckle 3,14 Echelon 4SC 3,15 Freehand 1.75G 2,3 Pursuit Plus 3,21 Snapshot Pyridine 3 Dimension 2EW, Dimension Ultra 40WP SEEDLING SHOOT LIPID SYNTHESIS 8/N Benzofuran 8 Nortron SC GROWTH INHIBITORS INHIBITOR (NOT ACCASE) Phosphorodithioate 8 Prefar 4-E Thiocarbamate 8 Bolero 8 EC 2,8 League MVP 3,8 Buckle 764

7 HERBICIDE SITES OF ACTION AND FAMILIES Site(s) Of Action (more than one Site Mode of Action (effect on plant growth)* Site of Action Group Herbicide Family of Action indicates PREMIX) Trade Name(s) SEEDLING ROOT LONG-CHAIN FATTY 15/K3 Chloroacetamide 15 Breakfree NXT, Charger Basic, Charger MAX, Cinch,Confidence, Dual GROWTH INHIBITORS ACID INHIBITORS II Magnum, Dual IIG Magnum, Dual Magnum, Harness, Outlook, (continued) (continued) Surpass NXT, Tower, Tremor NXT, Warrant 14,15 Authority Elite, BroadAxe XC, Prefix, Spartan Elite, Verdict, WarrantUltra 15,27 Armezon PRO, Zemax 15,27,27 Acuron Flexi 2,4,15 SureStart II, Threesidual, TripleFLEX II 3,15 Freehand 1.75G 4,15,27 Resicore 5,15 Bicep II Magnum, Bicep Lite II Magnum, Boundary 6.5 EC, Breakfree NXT ATZ, Breakfree NXT Lite, Charger MAX ATZ, Charger MAX ATZ Lite, Cinch ATZ Cinch ATZ Lite, Confidence Xtra, Confidence Xtra 5.6L, Degree Xtra, FulTime NXT, Harness Xtra, Harness Xtra 5.6L, Keystone LA NXT, Keystone NXT, Presidual, Tremor ATZ Lite NXT, Tremor ATZ NXT 5,15,27 Lexar EZ, Lumax EZ 5,15,27,27 Acuron 9,15 Sequence 9,15,27 Halex GT Oxyacetamide 5,15 Axiom DF Pyrazole 15 Zidua, Zidua SC 14,15 Anthem, Anthem Flex, Anthem Maxx, Fierce 2,14,15 Fierce XLT, Zidua PRO 5,14,15 Anthem ATZ DHP INHIBITOR DIHYDROPTEROATE 18/I Carbamate 18 Asulam 3.3, Asulox SYNTHETASE INHIBITORS UNDEFINED NUCLEIC ACID INHIBITOR 17/Z Arsenical 17 DSMA, MSMA 6 Plus POTENTIAL 26/L Quinoline Carboxylic Acid 2,4,26 Clearpath NUCLEIC ACID (For monocots; also group 4/0) INHIBITOR OR NONDESCRIPT MOA 2,4,26 Strada XT2 4,14,26 Solitare, SquareOne 4,26 Drive XLR8, Facet L CELLLULOSE/CELL WALL CELL WALL 20/L Nitrile 20 Casoron 4G SYNTHESIS INHIBITORS - SITE A CELL WALL 21/L Benzamide 21 Gallery 75 DF, Gallery SC INHIBITORS - SITE B 3,21 Snapshot CELLULOSE 29/L INHIBITORS - SITE C Alkylazine 29 Alion, EsplAnade 200 SC, Specticle Flo HERBICIDE SOA 765

8 HERBICIDE INJURY: MERISTEMATIC INHIBITORS I 1. Improper Leaf Unfurling of Corn 2. Corn Leaf-Out Underground 3. Leaf Puckering and Drawstring of Soybean HERBICIDE INJURY 4. Stunted, Twisted, Buggy- Whipped Corn 5. Stunted Plants and Crinkled Leaves: Soybean 6. Soybean Bud Seal 7. Stunted Corn With Swollen Proliferated Roots 8. Purple Corn Syndrome 9. DNA Soybean Injury 10. Lodged Soybeans 11. Corn Injury From Herbicide Carryover 766

9 HERBICIDE INJURY: MERISTEMATIC INHIBITORS I The meristematic inhibitors reduce the ability of meristems or regions of active cell division to develop and grow normally. Meristematic inhibitors can be divided into three categories: herbicides that primarily affect shoot meristems (Shoot Inhibitors), which include the acetanilide and thiocarbamate herbicides; herbicides that primarily affect root meristems (Root Inhibitors), which include the dinitroanilines; and herbicides that inhibit both root and shoot meristems or growing points (Shoot and Root Inhibitors), which include the imidazolinones, sulfonylureas, amino acid type herbicides and the postemergence grass herbicides. SHOOT INHIBITORS Chloroacetamides. This family of herbicides includes alachlor (several premixes), metolachlor (Dual and several premixes), and acetachlor (Harness, Surpass NXT). These herbicides translocate with the transpiration stream and primarily affect shoot meristems in sensitive plants. 1. Improper Leaf Unfurling of Corn. Stressful environmental conditions or excessive rates of alachlor, metolachlor or acetachlor may cause improper unfurling of corn leaves. Corn seedlings may appear malformed and stunted. Injured plants often outgrow this damage after emergence. Injury symptoms are similar to those caused by thiocarbamate herbicides. 2. Corn Leaf-Out Underground. Germinating corn injured by alachlor, metolachlor or acetachlor may result in plants leafing-out underground. This problem is more severe with deep planting, soil crusting, cool temperatures and certain sensitive hybrids. 3. Leaf Puckering and Drawstring of Soybeans. Acetanilide injury to soybeans may cause a slight puckering of the first few leaves. Injured plants may also show a drawstring effect where the midrib of the leaf is shortened, giving the injured leaves a heart-shaped appearance. Thiocarbamates. This family of herbicides includes butylate EPTC (Eptam). This family of herbicides translocates with the transpiration stream and primarily affects shoot meristems, so symptoms of injury can look very similar to acetanilide injury. 4. Stunted, Twisted, Buggy-Whipped Corn. Herbicides such as butylate and EPTC may cause stunting, twisting and buggy-whipping of some corn plants. 5. Stunted Plants and Crinkled Leaves: Soybean. Injury to soybean from butylate or EPTC can occur through either misapplication of the herbicides or planting of soybeans into a thiocarbamate treated field after a corn crop failure. Vernolate, a soybean herbicide, can cause similar injury symptoms. Injury symptoms include stunted plants with crinkled, malformed leaves. If the injury is not too severe, plants often recover and grain yields are unaffected. 6. Soybean Bud Seal. Severe soybean injury called bud seal may occur from misapplication of thiocarbamate herbicides. Soybeans may recover from all but the most severe bud seal injury. ROOT INHIBITORS Dinitroanilines (DNA). This herbicide family includes trifluralin (Treflan and Trust), pendimethalin (Framework, Prowl H2O), ethalfluralin (Sonalan), oryzalin (Surflan A.S.) and several premixes containing these DNA herbicides. The dinitroaniline herbicides translocate very little in plants and therefore primarily affect root meristems. 7. Stunted Corn with Swollen Proliferated Roots. Dinitroaniline herbicides such as trifluralin, pendimethalin, oryzalin and ethalfloralin may cause corn injury through misapplication or carryover of herbicide residues. Corn seedlings may appear stunted and chlorotic and develop proliferated, stubby root systems with club-shaped lateral roots. 8. Purple Corn Syndrome. Dinitroaniline or DNA induced root inhibition may cause corn plants to appear stunted, chlorotic and purple. Cool wet soils, fertility imbalance, compaction and other stresses that slow plant growth and development may accentuate injury. 9. DNA Soybean Injury. Excessive rates of dinitroaniline herbicides may result in early soybean injury denoted by pruned lateral roots, swollen and cracked hypocotyls, stunted plants and crinkled leaves. 10. Lodged Soybeans. Preemergence applications or shallow incorporation of dinitroaniline herbicides can occasionally cause symptoms of soybean injury that include girdling or callusing of plant stems at the soil surface. Later in the season, stems may easily break off (lodge). Injury may occur because of misapplication or where prolonged dry periods allow the chemical to remain in a concentrated layer near the soil surface. 11. Corn Injury from Herbicide Carryover. Carryover injury from any herbicide rarely appears uniformly throughout the field. Differences in herbicide rate and distribution, soil texture, organic matter content, ph, tillage, etc., often cause herbicide injury to appear in streaks or in isolated areas of the field. HERBICIDE INJURY Source: Revised from UNIVERSITY OF ILLINOIS March 1989 Curran et al. 767

10 HERBICIDE INJURY: MERISTEMATIC INHIBITORS II 1. Corn Stunting and Interveinal Chlorosis of Leaves 2. Bottle-Brush Corn Roots 3. Golden Beans 4. Leaves of Golden Beans 5. Red Veins 6. Slow Plant Death HERBICIDE INJURY 7. Chlorosis/Necrosis of Corn Leaves 8. Gradual Chlorosis/Necrosis of Soybean Leaves 9. Leaf Chlorosis, Necrosis and Grass Plant Death 10. Dead Grass Meristem 768

11 HERBICIDE INJURY: MERISTEMATIC INHIBITORS II SHOOT AND ROOT INHIBITORS Imidazolinones and Sulfonylureas. Both these herbicide families inhibit plant growth by preventing the synthesis of certain amino acids. These herbicides are systemic, having both foliar and soil activity, and are capable of stopping root and shoot growth, depending on the site of herbicide uptake. The imidazolinone herbicides include imazamox (Raptor), imazaquin (Scepter), imazethapyr (Pursuit) and several premixes containing imazaquin or imazethapyr. The sulfonylurea herbicides include chlorimuron (Classic) nicosulfuron (Accent Q), foramsulfuron (Revolver), thifensulfuron (Harmony SG). 1. Corn Stunting and Interveinal Chlorosis of Leaves. Imazaquin, imazethapyr or chlorimuron can injure corn through misapplication or through carryover of herbicide residues. Corn may appear stunted with interveinal chlorosis and/or purpling of the new leaves first. Risk of carryover injury from chlorimuron is much greater on soils with a ph above Bottle-Brush Corn Roots. Imidazolinones and sulfonylureas may inhibit root development of corn. With more severe injury, lateral roots are pruned. Short, proliferated roots may cause a bottle brush like appearance. 3. Golden Beans. Although soybean injury from imazaquin and chlorimuron applications is not common, it occurs more frequently on coarser-textured, lower organic matter soils. Soybean leaves may appear chlorotic and/or crinkled. The herbicide injury symptoms may appear similar to or be associated with those caused by potassium deficiency and/or soybean cyst nematodes. 4. Leaves of Golden Beans. An imidazolinone or sulfonylurea may cause soybean leaf margins to appear chlorotic to necrotic. Leaf yellowing may appear anywhere on the soybean plant (both the upper and lower portions of the plant). 5. Red Veins. The sulfonylurea herbicides can cause leaf veins to appear red or purplish. This is more frequently seen with susceptible weeds or less tolerant crops. 6. Slow Plant Death. Postemergence applications of the imidazolinones and sulfonylureas kill weeds slowly. Although plant growth may slow or stop shortly after application, injury symptoms are often unnoticed for two to three weeks after application. Amino Acid. The amino acid type herbicides include glyphosate (Cornerstone, Roundup, Rodeo). These translocated herbicides are nonselective, controlling both broad leaves and grasses. The amino acid herbicides are foliar applied materials, therefore injury symptoms first appear on the shoots of susceptible species. However, depending on the growth stage of the target species at application time (especially perennials), root inhibition may also occur. 7. Chlorosis/Necrosis of Corn Leaves. Glyphosate is the most common amino acid type herbicide. It is used for spot treatment of problem weeds in field crops and noncrop land. Glyphosate is very active on corn and is often applied with a ropewick. Crop injury occurs as a slow yellowing (chlorosis), followed by necrosis and plant death. 8. Gradual Chlorosis/Necrosis of Soybean Leaves. Glyphosate is often used for spot treatment of problem weeds in soybeans. However, if glyphosate comes in contact with soybean leaves, plant injury may occur. Newest soybean leaves will first appear chlorotic then may turn necrotic. Postemergence Grass Herbicides. The postemergence grass herbicides include clodinafop (Discover), fenoxaprop (Tacoma), fluazifop (Fusilade), haloxyfop (Verdict), sethoxydim (Poast), clethodim (Select 2 EC) and quizalofop (Assure II). These herbicides are systemic, controlling annual and some perennial grasses. They have little or no activity on broadleaf species. As with the amino acid herbicides, the postemergence grass herbicide injury symptoms first appear on the shoots of susceptible grass species. Root inhibition may also occur depending on plant growth stage and application timing. 9. Leaf Chlorosis, Necrosis and Grass Plant Death. The newest leaf tissue of treated grasses slowly turns chlorotic and then necrotic. This is eventually followed by plant death. 10. Dead Grass Meristem. A common symptom of ACC-ase herbicides such as Assure, Discover, Fusilade, Poast, Tacoma, and others. Young whorl leaves may be separated easily from the plant, indicating that the herbicide is acting on the plant meristem. HERBICIDE INJURY Source: Revised from UNIVERSITY OF ILLINOIS March 1989 Curran et al. 769

12 HERBICIDE INJURY: PHOTOSYNTHETIC INHIBITORS AND CONTACT HERBICIDES 1. Chlorosis/Necrosis of Older Corn Leaves 2. Chlorosis/Necrosis of Corn Leaf Tissue HERBICIDE INJURY 3. Interveinal Chlorosis and Yellowing of Soybean Leaves 4. Chlorosis and Necrosis of the Older Leaf Tissue in Soybean 5. Chlorosis and Necrosis of Older Leaf Tissue in Wheat 6. Necrotic Spots on Corn and Soybean Leaves 7. Necrotic Leaf Burn 8. Necrotic or Bronze Speckling on Soybean Leaves 770

13 HERBICIDE INJURY: PHOTOSYNTHETIC INHIBITORS AND CONTACT HERBICIDES Photosynthetic Inhibitors (PSI). The photosynthetic inhibitors include the triazines: atrazine, metribuzin (Dimetric EXT), simazine (Princep), and several premixes containing these active ingredients; the uracils: bromacil (Hyvar X and X-L) and terbacil (Sinbar); and the phenylureas: diuron (Karmex) and linuron (Lorox DF and Linex 4L). These herbicides all inhibit photosynthesis in susceptible plants. 1. Chlorosis/Necrosis of Older Corn Leaves. Chlorosis and necrosis of corn leaves, beginning at the leaf tips of older leaves, may result from application of atrazine or metribuzin. Injury is more likely following prolonged cool, wet conditions that stress the plant. 2. Chlorosis/Necrosis of Corn Leaf Tissue. Postemergence applications of linuron should be directed away from the corn leaves and onto the weeds. Plant tissue contacted by these herbicides may turn chlorotic, then necrotic. Symptoms from postemergence applications of photosynthetic inhibitor herbicides look similar to symptoms from contact type herbicide injury. Risk of injury is greater with the addition of crop oil. 3. Interveinal Chlorosis and Yellowing of Soybean Leaves. Interveinal chlorosis and necrosis of the older soybean leaf tissue may result from the use of a triazine herbicide such as metribuzin or a phenylurea herbicide such as linuron. With linuron, heavy rain may also splash treated soil onto the leaves causing necrotic spotting or splash burn. Plants can often recover from this splash burn injury if the buds are not affected. 4. Chlorosis and Necrosis of the Older Leaf Tissue in Soybean. Atrazine residues may carry over and cause soybean injury symptoms very similar to metribuzin or linuron injury. Atrazine residues in combination with metribuzin may cause additive injury to soybeans following corn. 5. Chlorosis and Necrosis of Older Leaf Tissue in Wheat. Wheat is sensitive to atrazine and may be injured from residues that carry over. Chlorosis and necrosis of the older leaf tissue first are symptoms of photosynthetic inhibitor herbicide injury to wheat. Contact Herbicides. The contact herbicides include a bipyridy-lium: paraquat (Gramoxone SL/SL 2.0); the diphenyl ethers: acifluorfen (Avalanche Ultra), lactofen (Cobra), fomesafen (Reflex) and Flexstar, and several premixes containing diphenyl ethers; and two others: bentazon (Basagran) and bromoxynil (Moxy 2E). The contact herbicides disrupt cell membranes and translocate very little in the plant. 6. Necrotic Spots on Corn and Soybean Leaves. Paraquat is a nonselective herbicide that kills plant tissue very quickly. Injury symptoms can be noticed within several hours after application, first as water-soaked areas on the leaf that turn to necrotic spots wherever spray drift contacted the leaves. 7. Necrotic Leaf Burn. The diphenyl ethers such as acifluorfen, lactofen and fomesafen may cause necrotic spotting or burn of leaf tissue contacted by herbicide spray. Slight leaf crinkling may also occur. Risk of injury from the diphenyl ethers is greater with the addition of crop oils and with applications made under high temperatures. Likelihood of soybean recovery is relatively good from this type of injury. 8. Necrotic or Bronze Speckling on Soybean Leaves. Soybeans generally have very good tolerance to bentazon (Basagran). However, under stress conditions or very warm temperatures, soybean leaves may show yellowing, bronzing, speckling or leaf burn. The addition of crop oil to the spray tank increases the risk of injury. Soybean injury is generally considered cosmetic only, with little risk of yield reduction. HERBICIDE INJURY Source: Revised from UNIVERSITY OF ILLINOIS March 1989 Curran et al. 771

14 HERBICIDE INJURY: PLANT GROWTH REGULATORS AND PIGMENT INHIBITORS 1. Onion Leafing in Corn 2. Elbowing, Lodging and Stalk Breakage in Corn 3. Corn Brace Root Injury 4. Missing Corn Kernels HERBICIDE INJURY 5. Improper Corn Root Development 6. Soybean Leaf Puckering and Cupping 7. Soybean Leaf Puckering/Distorted Growth 8. Soybean Stem Callus 8a. Soybean Stem Callus 10. Chlorotic/White Corn 11. Chlorotic/White Small Grains 12. Off-Target Bleaching 772

15 HERBICIDE INJURY: PLANT GROWTH REGULATORS AND PIGMENT INHIBITORS Plant Growth Regulators-PGRs (Growth hormones, sythetic auxins). The growth regulator type herbicides include the benzoic acids: dicamba (Sterling Blue or Banvel or Dicamba Max 4; the phenoxy acetic acids which include 2,4-D, 2,4-DB (Butyrac), and MCPA; and the pyridines: picloram (Tordon) triclopyr (Garlon 3A, Garlon 4, Garlon 4 Ultra and a component of Crossbow), clopyralid (Stinger), aminopyralid (Milestone) and fluroxypyr (Starane Ultra). All of these compounds are systemic. The plant growth regulator herbicides mimic different growth regulating compounds in the plant and may cause a variety of growth abnormalities in susceptible species. The injury symptoms generally are first seen in the newest leaves. Some injury symptoms may resemble those caused by meristematic inhibitor compounds. 1. Onion Leafing in Corn. 2,4-D applied postemergence may injure corn. Symptoms can include onion leafing, elbowing and malformed brace roots. Certain corn hybrids are more sensitive to 2,4-D than others. Corn may occasionally be injured by applications of dicamba, however, the risk of injury may be less than with 2,4-D. Injury symptoms of dicamba are similar to those caused by 2,4-D. 2. Elbowing, Lodging and Stalk Breakage in Corn. Corn stalks may become brittle for one or two weeks following 2,4-D application, increasing the risk of stalk breakage by wind or cultivation equipment. Excessive rates of 2,4-D, may result in elbowing or lodging of corn stalks, particularly when sensitive hybrids are grown. Elbowing and lodging symptoms in corn may look similar to damage caused by corn rootworm larvae. Avoid applying 2,4-D or dicamba to corn which is under stress from adverse weather conditions. 3. Corn Brace Root Injury. Excessive rates of 2,4-D or dicamba may cause malformation of corn brace roots, resulting in proliferation of roots, fusing or fasciation of roots and roots growing upward rather than downward. 4. Missing Corn Kernels. Postemergence applications of 2,4-D and dicamba during the period from tassel to dough stage may result in lack of kernel set or ear development. 5. Improper Corn Root Development. The primary root system in seedling corn may appear proliferated and stubby where excessive rates of dicamba applied preemergence or a misapplication of chloramben contacts the germinating seed. 6. Soybean Leaf Puckering and Cupping. Dicamba applications to corn, small grains or noncropland may drift and injure nearby soybeans and other desirable vegetation. Cupped and puckered leaves and abnormal bud development are symptoms of dicamba injury. Dicamba and 2,4-D drift injury look similar. 7. Soybean Leaf Puckering/Distorted Growth. 2,4-D applied postemergence to corn may drift and injure nearby soybeans and other desirable plants. Symptoms of injury include puckering of leaves, parallel venation or leaf strapping, distortion of stems, callus growth and lodging. 2,4-DB applied postemergence over the top to soybeans can cause similar symptoms. 8. Soybean Stem Callus. Early season injury to soybeans from 2,4-D or 2,4-DB may cause abnormal growth near the soil surface which can result in soybean lodging. 9. Pigment Inhibitors (Bleachers). The pigment inhibitors include clomazone (Command 3ME), isoxaflutole (Balance Flexx), tombotrione (Laudis), topramezone (Impact) and mesotrione (Callisto). These herbicides inhibit the production of photosynthetic pigments in the plant. The pigment inhibitors are soil active, with intermediate to long soil persistence. Clomazone is registered for use in soybeans and may injure corn, small grains, forage legumes and ornamentals through misapplication, drift or carryover. 10. Chlorotic/White Corn. Corn injury from clomazone can occur through misapplication, drift or carryover. Shortly after emergence, the corn may appear chlorotic, then bleached or white. The likelihood of corn recovering from clomazone injury is good as long as a portion of the plant remains green. Various inbreds and hybrids may respond differently to clomazone residues. Other pigment inhibitors may cause similar symptomology. 11. Chlorotic/White Small Grains. Small grains such as wheat and oats are very sensitive to clomazone residues. Plants appear chlorotic or bleached (white). Other pigment inhibitors may cause similar symptomology. 12. Off-Target Bleaching. Preemergence applications of clomazone may move off-target by particle or vapor drift. Sensitive ornamentals may appear chlorotic or white. Unless injury is severe, plants generally recover from clomazone injury due to movement outside the target area. Other pigment inhibitors may cause similar symptomology. HERBICIDE INJURY Source: Revised from UNIVERSITY OF ILLINOIS March 1989 Curran et al. 773

16 HERBICIDE PROPERTIES AFFECTING PERFORMANCE The table on the following page presents information which can help in the more effective use of common herbicides and avoid contamination of the environment through drift, runoff and leaching of the herbicide. A description of these herbicide properties is listed below. HERBICIDE PROPERTIES Properties Affecting Performance, Runoff and Leaching 1. Soil Degradation a) Microbial decomposition is the most common pathway by which herbicides degrade. Herbicides vary greatly in their susceptibility to this process (herbicides with asterisks are most susceptible). The rate of microbial breakdown is affected by temperature, moisture, soil ph and soil organic matter. A warm (80-90 F), moist, well-aerated soil with ph of is most favorable for rapid microbial breakdown. Any adverse condition, such as cold temperatures or dry soil, will increase the residual or carryover potential. b) Chemical Decomposition is not biological and is influenced somewhat less by changes in soil moisture and temperature. In general, high soil temperature increases the rate of chemical breakdown. As a result, breakdown of chemicals subject to chemical decomposition proceeds at a near normal pace in dry, hot seasons. High ph reduces the rate of chemical breakdown of sulfonylurea and triazine herbicides. Low ph reduces the rate of breakdown of Pursuit and Scepter. 2. Surface Loss a) Photodecomposition is the decomposition of herbicides by ultraviolet rays from sunlight. Soil-applied herbicides with high ratings should be incorporated. b) Volatility is the conversion of a herbicide to a gaseous form. High volatility ratings imply that soil-applied herbicides should be incorporated and that post-applied herbicides may volatilize and drift to susceptible plants. High temperature, moist soils and wind are factors which increase the rate of volatilization. Volatility of soilapplied herbicides is greater from moist than from dry soil. Volatility into soil pore spaces improves the mobility and root uptake of some soil-applied herbicides. 3. Water Solubility The higher the solubility, the greater the tendency for a herbicide to move with water. High solubility of soil-applied herbicides is desirable for dry soil conditions since it requires a minimal amount of rain for activation. A disadvantage of high solubility is that excessive rainfall can leach the herbicide out of the zone of weed seeds and roots. A second disadvantage of high solubility is an increased potential to leach into groundwater. Water Solubility Classes of Pesticides Solubility Solubility Class (ppm) >3,000 Very high High Moderate 3-30 Low <3 Very low 4. Soil Adsorptivity The strength of bonding of a herbicide to soil clay and organic matter affects herbicide mobility and the rate required for weed control. Soil applied herbicides with strong soil adsorptivity require large adjustments in rate for different soil types. Post emergence herbicides with strong soil adsorptivity generally have little or no soil residual activity. Herbicides with low soil adsorptivity are often good choices for fields with wide variation in soil characteristics. Low adsorptivity increases the potential for a herbicide to runoff or leach into groundwater. 5. Half-life (Soil Persistence or Residual) The length of time a herbicide persists in the soil is affected by all the factors listed above. Since half-life (soil residual) is affected by rate, soil properties, environmental conditions, plant species and many other factors, it is not possible to determine the exact length of time that a herbicide will control weeds or carryover to affect plant-back crops. The days of activity listed in the following table are only general guidelines on the relative persistence of herbicides. The actual value in the field may be lower than the value listed when conditions for rapid breakdown exist or higher than the listed value where breakdown is slow or the use rate is excessive. PESTICIDE MOVEMENT IN WATER INTO SURFACE WATERS OR UNDERGROUND Physical and chemical properties affect the potential movement of pesticides into surface water as runoff or into groundwater through leaching. The effect of these properties (shown on the following pages) on pesticide movement can be summarized as follows: Relative Persistence or Half Life The slower a pesticide degrades, the greater the chances it will move into ground or surface waters. Water Solubility The higher the water solubility (generally over 30 ppm), the higher the potential for leaching into groundwater and for surface runoff into streams, reservoirs, etc. Soil Adsorptivity The weaker the pesticide is bonded to soil particles, the greater the potential for that pesticide to be found in water. MOVEMENT OF PESTICIDES ATTACHED TO SOIL SEDIMENT As with leaching and surface runoff, movement of pesticides attached to soil increases as the length of persistence increases. Low solubility and strong soil absorptivity favor movement with soil particles. 774

17 HERBICIDE PROPERTIES AFFECTING PERFORMANCE Plant Uptake Soil Degradation 1,2 Surface Loss 1,3 Water Soil Half-life under F = Foliar Photo- Solubility 1 Adsorptivity 1,4 field conditions Trade Name S = Shoot R = Root Microbial Chemical decomposition Volatility (ppm at 77 F) (Koc); Mobility (days) 3 2,4-D, dimethylamine salt F/R L M 796,000 20; Mobile 10 2,4-D, 2-ethylhexyl ester F/R L M-H 1 46; Mobile 34 2,4-DB, dimethylamine salt F L L 709,000 20; Mobile 10 Acetochlor S/R L L ; Mobile 14 Acifluorfen F H L 250, ; Moderately Mobile 54 Aminocyclopyrachlor F/S/R L L 3,130-3,870 28; Mobile 100 Aminopyralid F/R L L 212, ,000 13; Mobile 35 Atrazine R/F M L ; Mobile 60 Bentazon F/R L L ; Mobile 13 Bromacil R L L ; Mobile 60 Bromoxynil octonoate F L L ,000; Hardly Mobile 7 Carfentrazone-ethyl F L L ; Moderately Mobile 4 Chlorimuron-ethyl F L L ; Mobile 40 Chlorsulfuron F/R L L 7,000 40; Mobile 40 Clethodim F/S L-M L 5,450 40; Mobile 3 Clodinafop-propargyl F M-H L 4 1,500; Slightly Mobile 1 Clomazone S/R L M-H 1, ; Moderately Mobile 24 Clopyralid, monoethanolamine salt F/R NA L L 300,000 6; Highly Mobile 40 Cloransulam-methyl R/S L L 3-3,430 30; Mobile 11 Cyhalofop-butyl F L L ,523; Slightly Mobile 1 Dicamba, amine salts F/R/S L-M M-H 400,000 2; Highly Mobile 14 Dimethenamid-p S/R L L 1, ; Moderately Mobile 31 Diquat dibromide F L L 718,000 1,000,000; Immobile 1,000 Diuron R L L-M ; Moderately Mobile 90 EPTC S/R L H ; Moderately Mobile 6 Ethalfluralin S/R M L 0.3 4,000; Slightly Mobile 60 Florasulam F/R L L 6,360 22; Mobile 8.5 Fluazifop-p-butyl F L L 2 5,700; Slightly Mobile 15 Flucarbazone-sodium F/R L L 44,000 20; Mobile 15 Flufenacet R/S L L ; Moderately Mobile 199 Flumetsulam R/F L L 5,650 28; Mobile 47 Flumiclorac-pentyl ester F L L ; Mobile 2.5 Flumioxazin F/R L L ,242; Slightly Mobile 14.7 Fluroxypyr 1-methylheptyl ester F L L ,600; Hardly Mobile 36 Fluthiacet-methyl F H NA ; Mobile 8 Fomesafen F/R H L 700,000 60; Mobile 100 Foramsulfuron F NA L L ; Mobile 15 Glufosinate-ammonium F NA L L 1,370, ; Mobile 7 Glyphosate 6 F L L 900,000 24,000; Hardly Mobile 47 Halauxifen-methyl F/S/R L L ; Mobile 7 Halosulfuron-methyl F/R L L ; Mobile 26.7 Hexazinone R/F NA M-H L 33,000 54; Mobile 90 Imazamethabenz-methyl R/S L-M L ; Mobile 45 Imazamox F/R L L 626,000 67; Mobile 17 Imazapic, ammonium salt R/F NA L 259,000 81; Mobile 1,200 Imazapyr R/F L L 11, , ; Mobile 90 Imazaquin R/S L-M L 160,000 20; Mobile 60 Imazethapyr F/R L L 200,000 10; Highly Mobile 90 Isoxaflutole 5 F/S/R L-M L ; Moderately Mobile 1 Lactofen F M-H L ,000; Sightly/Hardly Mobile 3 Linuron R/F L L-M ; Moderately Mobile 60 MCPA 7 F/S/R L L-M ; Mobile 25 MCPP 7 F/R L NA ; Mobile 13 Mesosulfuron-methyl F/R NA L , ; Moderately Mobile 78 Continued HERBICIDE PROPERTIES 775

18 HERBICIDE PROPERTIES AFFECTING PERFORMANCE HERBICIDE PROPERTIES Plant Uptake Soil Degradation 1,2 Surface Loss 1,3 Water Soil Half-life under F = Foliar Photo- Solubility 1 Adsorptivity 1,4 field conditions Trade Name S = Shoot R = Root Microbial Chemical decomposition Volatility (ppm at 77 F) (Koc); Mobility (days) 3 Mesotrione F/S/R L L ; Moderately Mobile-Mobile 18 Metribuzin R/F L L 1,220 60; Mobile 40 Metsulfuron-methyl F/R L L ; Mobile 120 Nicosulfuron F NA L 22,000 30; Mobile 21 Norflurazon R M-H NA ; Moderately Mobile 90 Paraquat dichloride F M L 620,000 1,000,000; Immobile 1,000 Pendimethalin S/R L L-M ,000; Slightly Mobile 90 Penoxsulam F/S/R L-M L 5.7-1,460 94; Mobile 15 Picloram F/R M-H L 200,000 16; Mobile 90 Pinoxaden F/R L L ; Moderatley Mobile 3 Primisulfuron-methyl F/R M L 70 50; Mobile 30 Prodiamine S/R M-H L-M ,000; Hardly Mobile 120 Prometon R/F NA M L ; Moderately Mobile 500 Propoxycarbazone-sodium F/R L-M L 42,000 29; Mobile 23 Prosulfuron F/S/R L L 4,000 14; Mobile 62 Pyrasulfotole F NA L 4,200-49, ; Moderately Mobile 12 Pyrithiobac-sodium F/R H L 728 9; Highly Mobile 60 Pyroxasulfone S/R L L ; Moderately Mobile 21 Pyroxsulam F L L , ; Mobile 14 Quinclorac F/S/R L L ; Mobile 450 Quizalofop-p-ethyl F L NA 0.4 1,816; Slightly Mobile 60 Rimsulfuron F NA L 7,300 47; Mobile 10 s-metolachlor S/R M-H L-M ; Moderately Mobile 15 Saflufenacil F/S/R L-M L 14-2, ; Moderately Mobile 18 Sethoxydim F NA H L 4, ; Mobile 5 Simazine R M L ; Mobile 60 Sulfentrazone R/F NA L L ; Mobile 541 Sulfometuron-methyl F/R L L 70 78; Mobile 20 Sulfosulfuron F H L 1,627 33; Mobile 45 Tebuthiuron R NA L L 2,500 80; Mobile 360 Tembotrione F/S/R L L ; Mobile 40 Terbacil R NA L L ; Mobile 120 Thiencarbazone-methyl F/R L L ; Moderately Mobile 29 Thifensulfuron-methyl F/R NA L 2,400 45; Mobile 12 Thiobencarb R/S NA L-M L-M ; Moderately Mobile 21 Topramezone F/S/R L-M L 15, ; Mobile 160 Tralkoxydim F/R L L 6 20; Mobile 18 Triallate S NA L M-H 4 2,400; Slightly Mobile 82 Triasulfuron F/R L-M L ; Mobile 59.1 Tribenuron-methyl F/R L L ; Mobile 10 Triclopyr F M L ; Mobile 13 Trifluralin S H M 0.3 8,000; Slightly Mobile 60 Triflusulfuron-methyl F L L ,000 58; Mobile 3 1 See preceding pages for explanation of these properties. First value in a range linked to lower soil ph or acid formulations; second value linked to higher soil ph or salt formulations. 2,, = Minor, Secondary (or ph-dependent), or Major Factor, respectively; NA = Not applicable as a factor due to stability, soil ph, adsorption or other factors, or because value is unknown. (Chemical degradation of sulfonyureas is reduced as soil ph increases.) 3 L,M,H = Low, Medium, High, respectively; NA = Not applicable as a mechanism 4 < 10 ml/g = Highly Mobile; = Mobile; 100-1,000 = Moderately Mobile; 1,000-10,000 = Slightly Mobile; 10, ,000 = Hardly Mobile; > 100,000 = Immobile 5 Isoxaflutole is rapidly converted in soil to herbicidally active ingredient Diketonitrile which has greater solubility and mobility. 6 These herbicides bond quickly to soil and are inactive shortly after application. 7 MCPA and MCPP salt formulaitons dissociate rapidly in soil to their less soluble acid forms; water solubility values are for MCPA and MDCA acids. for loss, or value is unknown. 776