turfgrass herbicide families & mode-of-action
DESCRIPTION
Turfgrass Herbicide Families & Mode-of-Action. Tim R. Murphy The University of Georgia. Herbicide Mode-of Action. Mode-of-Action - The entire sequence of events that happen from the time the herbicide is absorbed to the eventual plant response (usually death). Mode of Action. Three phases - PowerPoint PPT PresentationTRANSCRIPT
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Turfgrass HerbicideFamilies & Mode-of-Action
Tim R. Murphy
The University of Georgia
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Mode-of-Action - The entire sequence ofevents that happen from the time the herbicide is absorbed to the eventual plant response (usually death).
Herbicide Mode-of Action
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Mode of Action
Three phases* Absorption* Movement to target site* Inhibit biochemical reaction
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Herbicide Mode-of-Action
The way a herbicide kills or inhibits the growth of susceptible plants!!
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Why understand herbicide MOA?
Better understanding of how herbicides perform.
Diagnosing herbicide injury. Professionalism. Public relations.
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Herbicide Classification
Selectivity Herbicide movement in plants Timing of application Chemical Family Mode of Action
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Herbicide Classification - Selectivity
Selective controls or suppresses one species of plant
without seriously affecting the growth of another plant species.
Example2,4-D will control many broadleaf weeds without
seriously affecting turfgrasses.
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Herbicide Classification - Selectivity
Nonselective Nonselective herbicides control plants
regardless of species. Examples
Roundup Pro, Finale, Reward, Scythe
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Xylem - nonliving tissue in a plant that transports water and mineral nutrients from the roots to the shoots.
Phloem - living tissue that transports sugars from the site of synthesis or storage to the site of use.
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Phloem mobile herbicides move up and down in the plant
Xylem mobile herbicides move up in the plant
Contact herbicides do not move in the plant
Translocated herbicides move.
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Contact Rupture cell
membranes. Symptoms
appear within hours.
Need complete coverage for kill.
Xylem MobileTaken up by primarily by roots.Found in older leaves that are exporting sugars.
Do not move downward when foliar applied.
Phloem MobileMove to points of active growth or food storage.Affect shoot tips, young buds and leaves.Can cause contact burn.
Herbicide Movement in Plants
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Mode-of-Action
Retention Absorption Translocation to active cell site Inhibit biochemical reaction Plant metabolism or breakdown
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Plant leaf cuticle.
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Plant Processes Affected by Turfgrass Herbicides
Photosynthesis Amino acid and protein synthesis Cell division Cell membranes Growth regulation Growth inhibition Fatty acid synthesis
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Photosynthesis
CO2 + H2O + Sunlight = C6H12O6
OR
Carbon dioxide + water + sunlight
will yield
Sugar
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Triazines
Atrazine – Aatrex, Simazine - Princep Metribuzin – Sencor Used only on warm-season turfgrasses Root and shoot absorbed (except simazine) Inhibits photosynthesis, eventual membrane
disruption, requires light Pre and Post control
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Light and active photosynthesis needed for activity
These herbicides interrupt energy flow resulting in free radicals
Free radicals react with cell membranes
Photosynthetic inhibitors
Atrazine on bentgrass
Atrazine, simazine, Sencor
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Ethofumesate
Prograsscool-season grasses and overseeded
bermudagrassprimarily shoot absorbed, some by rootsnot well absorbed after leaf cuticle is formedtranslocated if root or shoot absorbedappears to inhibit photosynthesis and
respiration, not well understood
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Bentazon
Basagran T/OAll warm- and cool-season turfgrassescontact, foliage absorbedlimited translocationcan move in xylem if root absorbedinhibits photosynthetic electron transport
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Photosynthesis Inhibitors
Symptomology Interveinal or veinal yellowing followed
by death of plant tissue from leaf margins inward
POST applications cause rapid browning of plant tissue
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BladexBladexCotoran
Source: W. K. Vencill, UGA
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Amino acids
Building blocks of plant proteinsEnzymes mediate biochemical
reactionsStorage roles - seed reservesStructural roles
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Amino Acid Synthesis Inhibitors
Characteristics Most of these herbicides have soil and foliar
activity except glyphosate Undergo significant translocation Soil residual activity herbicide-dependent Generally, low use-rate herbicides
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Amino Acid Synthesis Inhibitors
Symptomology Injury symptoms on grass include stunting, purple
coloration, and inhibited root systems with “bottle-brush” appearance
Broadleaf plant symptomology includes formation of red or purple leaf veins, yellowing of new leaf tissue and blackening of terminal growth
Glyphosate injury includes initial yellowing followed by death of affected tissue
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Imidazolinones
Image, Plateauwarm-season grasses, except bahiagrassrapid shoot and root absorptiontranslocates to meristematic areasinhibits leucine, isoleucine and valine synthesisgrowth is impaired and plants die over 1 to 3 wk
period
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Image on bermuda
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Sulfonylureas
Manor, Corsair, SedgeHammer,TranXit, Monument, Revolver, Certaintyrapid shoot and root absorptiontranslocates to meristematic areasinhibits leucine, isoleucine and valine synthesisgrowth is impaired and plants die over 1 to 3 wk
period
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Pyrimidunyloxybenzoic
Velocity Overseeded bermudagrass
rapid shoot and root absorptionTranslocated via phloeminhibits leucine, isoleucine and valine synthesisgrowth is impaired and plants die over 2 to 3 wk
period
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Glyphosate
Isopropylamine salt - Roundup Pro , GlyphoMate 41, Razor Pro, Prosecutor
Ammonium salt - Roundup ProDry Diammonium salt - TouchDown Pro
foliage absorbedextensively translocated in phloem inhibits tryptophan, tyrosine and phenylalanine synthesisgrowth is impaired and plants die over 1 to 3 wk period
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“dormant” zoysiagrass
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Green under “dormant” zoysiagrass
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“Dormant zoysiagrass” spot sprayed with Roundup
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Cell Division
Plant growth is due to cell division and cell elongation.
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Dinitroanilines Benefin - Balan Oryzalin - Surflan Pendimethalin - Pendulum Prodiamine - Barricade Trifluralin - Treflan
Shoot and root absorbed, no translocation Inhibit cell division (tubulin formation)Used on most warm- and cool-season turfgrasses
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Dithiopyr
Dimension MOA is similar to dinitroanilines
Shoot and root absorbed, no translocationInhibit cell division (tubulin formation)Has POST activity on seedling crabgrassUsed on most warm- and cool-season
turfgrasses
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DNA Root inhibition
pendimethalin on zoysiagrass Dimension on
bermudagrass
Surflan on St. Augustinegrass
Swollen, club shaped roots
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Pronamide
Kerbroot absorbed, translocated in xylemcontrols emerged cool-season grassesinhibits cell divisionUsed only on warm-season turfgrasses
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Cell Membranes
Contain the cellular contents and regulate the entry and exit of substances that promote or inhibit plant metabolism
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Diquat Reward LS
contact, very rapidly absorbed,does not translocate requires light for activitydisrupts electron flow in photosynthesis leads to formation of free radicals which damages cell
membranescellular fluids leak, followed by deathused on dormant bermudagrass
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Glufosinate Finale
readily absorbed by leavesprimarily contact activity, limited translocation inhibits key enzyme involved in conversion of ammonia
into amino acids toxic levels of ammonia build up, causes cell membrane
disruption, interferes with photosynthesisused on dormant bermudagrass
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Cell Membrane Disrupters
Damage occurs within hours. Membrane destruction. No redistribution Complete coverage for kill.
Finale on zoysia
Finale, Reward, Paraquat
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Organic Arsenicals
MSMA, DSMA, CMA, CAMAfoliage absorbedMobile in xylem and phloemNot well understood, rapid desiccation indicates
cell membrane destructionUsed on cool-season grasses, bermuda and
zoysiagrass
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Leaf burn on broadleaves and grasses with yellow leaf tips on grasses
Terminal yellowing of grasses
MSMA on zoysia
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MSMA injury on tall fescue
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Tee infested with Texas sedge
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Texas sedge tee after treatment with MSMA
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Oxadiazon
Ronstarall turfgrasses, except centipedereadily shoot absorbed, less so by rootscan be foliage absorbed, “contact burn”does not significantly translocateLight requiredinhibits key enzyme in chlorophyll synthesis,
toxic radicals formed, disrupts cell membranes
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Oxadiazon (Ronstar)
PRE 2G – Ky. Bluegrass, Bermuda, seashore
paspalum, t. fescue, zoysia, St. Augustine 50WSP – bermuda, St. Augustine, zoysia Annual grasses, selected broadleaves
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Ronstar 2G and 50WSP - At Sprigging
Apply immediately before or after sprigging bermudagrass and zoysiagrass
Pre-sprigging (1 day before sprigging slightly safer than post-sprigging)
Irrigate ASAP for best results
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Carfentrazone
QuickSilverContact, quickly absorbedFast-actingInhibits enzyme (protoporphyrinogen oxidase) in
chlorophyll synthesis pathway. Leads to formation of toxic intermediates which disrupt cell membranes.
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Carfentrazone
Sold with phenoxy herbicides and dicamba as PowerZone and SpeedZone
All turfgrasses does not significantly translocate
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Sulfentrazone
DismissRoot and shoot absorbedFast-actingInhibits enzyme (protoporphyrinogen oxidase) in
chlorophyll synthesis pathway. Leads to formation of toxic intermediates which disrupt cell membranes.
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Carfentrazone and Sulfentrazone
Carfentrazone – POST, all turfgrassses
Sulfentrazone – PRE, although does have POST activity
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Growth Regulation
Naturally produced hormones (auxins, cytokinins, gibberellins, others) are involved in the regulation of normal growth and development.
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Growth Regulator Herbicides
These herbicides affect several plant processes such as cell division, cell enlargement, protein synthesis and respiration. They act by upsetting the normal hormonal balance in plants.
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Growth Regulator Herbicides
Phenoxys 2,4-D, dichlorprop mecoprop, MCPA
Benzoics Banvel, Vanquish
Picolinic Acids Confront Turflon Lontrel SpotLight
Quinolinecarboxylic Drive
Trimec on bermuda
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Phenoxy, Benzoic Acid, Picolinic Acid
readily absorbed by foliage, less so by roots extensively translocated interfere with DNA, RNA and protein
synthesis results in uncontrolled cell division and
elongation vascular tissues are plugged, 1 to 3 wks
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Quinclorac
Driveshoot and root absorbed readily translocates in xylem and phloemMOA not fully understoodBroadleaf's - alters auxin levelsGrasses - affects cell wall synthesis, increases cyanide
and ethylene productionUsed on tall fescue, zoysia and bermudagrass, Ky
bluegrass
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Drive on crabgrass, 7 days after treatment
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Growth Regulator HerbicidesSymptomology
Broadleaf plant stem twisting and curling Leaves on broadleaf plants exhibit
cupping, crinkling, strapping, or drawstring affect
Symptoms on grass plants include leaf rolling, crinkling, brace root fusion and malformation.
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2,4-D overdose on St. Augustinegrass
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2,4-D Injury on Soybean
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Growth Inhibition
Exact MOA not known Inhibit root and shoot growth Disrupt cell division, cell enlargement Also may disrupt lipid synthesis, nucleic acid
and protein synthesis
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Growth Inhibitors
Bensulide - Betasan, Pre-Sanroot absorbed, essentially no translocationdisrupts cell division and enlargement
Metolachor - Pennantmainly shoot absorbed, some root uptaketranslocates in xyleminhibit root and shoot growthdisrupts protein, fatty acid and lipid synthesis
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Growth Inhibitors
Siduron - Tupersanreadily absorbed by roots, translocated in xyleminhibits root growth, may disrupt mitosisUsed only on cool-season turfgrasses and
zoysiagrass
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Growth Inhibitors
Galleryrapidly absorbed by roots, minimal foliage
absorptionmoves in xylem inhibits cell wall biosynthesisUsed on all cool- and warm-season turfgrasses
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Fatty Acid Synthesis
Fatty acids are important components of cell membranes
Inhibition fatty acid synthesis blocks production of lipids needed for new cell growth.
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Fatty Acid Inhibitors
Cyclohexanedionessethoxydim - Vantage, Poastused only on centipedegrass and fine fescueclethodim – Envoyused only on centipedegrass
Rapidly absorbed by leaves, extensively translocated via phloem to meristems
Inhibit key enzyme in fatty acid synthesis
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Fatty Acid Inhibitors
Aryl-oxy-phenoxiesfenoxaprop - Acclaim Extrafluazifop - Fusilade IIdiclofop - Illoxan
Rapidly absorbed by leaves, extensively translocated via phloem to meristems, (diclofop translocation is slow)
Inhibit key enzyme in fatty acid synthesis
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Fatty Acid Synthesis Inhibitors - Grass Herbicides
Reddening of leaf tissue.
Discoloration of tissue at and above the nodes.
Tissue and leaves in the leaf whorl can easily be separated from the rest of the plant.
No broadleaf activity.
Fusilade on dallisgrass
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Fatty Acid Synthesis Inhibitors
Initial injury in meristematic regions occurs where newest leaves are developing
These regions will turn chlorotic, which is followed by necrosis
The affected area will become “rotted” and will easily separate from rest of plant
Injury will develop slowly (7 to 14 days)
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Source: W. K. Vencill, UGA
“rotted” meristem
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TurfWeedManagement
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