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Turfgrass Herbicide Families & Mode-of-Action

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Presentation on theme: "Turfgrass Herbicide Families & Mode-of-Action"— Presentation transcript:

1 Turfgrass Herbicide Families & Mode-of-Action
Tim R. Murphy The University of Georgia

2 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).

3 Mode of Action Three phases Absorption Movement to target site
Inhibit biochemical reaction

4 Herbicide Mode-of-Action
The way a herbicide kills or inhibits the growth of susceptible plants!!

5 Why understand herbicide MOA?
Better understanding of how herbicides perform. Diagnosing herbicide injury. Professionalism. Public relations.

6 Herbicide Classification
Selectivity Herbicide movement in plants Timing of application Chemical Family Mode of Action

7 Herbicide Classification - Selectivity
Selective controls or suppresses one species of plant without seriously affecting the growth of another plant species. Example 2,4-D will control many broadleaf weeds without seriously affecting turfgrasses.

8 Herbicide Classification - Selectivity
Nonselective Nonselective herbicides control plants regardless of species. Examples Roundup Pro, Finale, Reward, Scythe

9 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.

10 Translocated herbicides move.
Contact herbicides do not move in the plant Phloem mobile herbicides move up and down in the plant Xylem mobile herbicides move up in the plant Translocated herbicides move.

11 Herbicide Movement in Plants
Contact Rupture cell membranes. Symptoms appear within hours. Need complete coverage for kill. Xylem Mobile Taken up by primarily by roots. Found in older leaves that are exporting sugars. Do not move downward when foliar applied. Phloem Mobile Move to points of active growth or food storage. Affect shoot tips, young buds and leaves. Can cause contact burn.

12 Mode-of-Action Retention Absorption Translocation to active cell site
Inhibit biochemical reaction Plant metabolism or breakdown

13 Plant leaf cuticle.


15 Plant Processes Affected by Turfgrass Herbicides
Photosynthesis Amino acid and protein synthesis Cell division Cell membranes Growth regulation Growth inhibition Fatty acid synthesis

16 Photosynthesis CO2 + H2O + Sunlight = C6H12O6 OR
Carbon dioxide + water + sunlight will yield Sugar

17 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

18 Photosynthetic inhibitors
Atrazine, simazine, Sencor Light and active photosynthesis needed for activity These herbicides interrupt energy flow resulting in free radicals Free radicals react with cell membranes Atrazine on bentgrass

19 Ethofumesate Prograss cool-season grasses and overseeded bermudagrass
primarily shoot absorbed, some by roots not well absorbed after leaf cuticle is formed translocated if root or shoot absorbed appears to inhibit photosynthesis and respiration, not well understood

20 Bentazon Basagran T/O All warm- and cool-season turfgrasses
contact, foliage absorbed limited translocation can move in xylem if root absorbed inhibits photosynthetic electron transport

21 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

22 Bladex Cotoran Source: W. K. Vencill, UGA

23 Amino acids Building blocks of plant proteins
Enzymes mediate biochemical reactions Storage roles - seed reserves Structural roles

24 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

25 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

26 Imidazolinones Image, Plateau warm-season grasses, except bahiagrass
rapid shoot and root absorption translocates to meristematic areas inhibits leucine, isoleucine and valine synthesis growth is impaired and plants die over 1 to 3 wk period

27 Image on bermuda

28 Sulfonylureas Manor, Corsair, SedgeHammer,TranXit, Monument, Revolver, Certainty rapid shoot and root absorption translocates to meristematic areas inhibits leucine, isoleucine and valine synthesis growth is impaired and plants die over 1 to 3 wk period

29 Sulfonylureas Manor, Blade – warm-season grasses, except bahiagrass; also on Ky. Bluegrass Corsair – Ky. Bluegrass, bahiagrass, bermudagrass SedgeHammer– all warm- and cool-season turfgrasses Revolver – bermuda, ‘Meyer’ zoysia Monument – bermuda, zoysia TranXit – bermuda, zoysia, centipede, overseeded bermudagrass Certainty – bermuda, zoysia, centipede, St. Augustine

30 Pyrimidunyloxybenzoic
Velocity Overseeded bermudagrass rapid shoot and root absorption Translocated via phloem inhibits leucine, isoleucine and valine synthesis growth is impaired and plants die over 2 to 3 wk period

31 Glyphosate Isopropylamine salt - Roundup Pro , GlyphoMate 41, Razor Pro, Prosecutor Ammonium salt - Roundup ProDry Diammonium salt - TouchDown Pro foliage absorbed extensively translocated in phloem inhibits tryptophan, tyrosine and phenylalanine synthesis growth is impaired and plants die over 1 to 3 wk period

32 “dormant” zoysiagrass

33 Green under “dormant” zoysiagrass

34 “Dormant zoysiagrass” spot sprayed with Roundup

35 Cell Division Plant growth is due to cell division and cell elongation.

36 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

37 Dithiopyr Dimension MOA is similar to dinitroanilines
Shoot and root absorbed, no translocation Inhibit cell division (tubulin formation) Has POST activity on seedling crabgrass Used on most warm- and cool-season turfgrasses

38 DNA Root inhibition Swollen, club shaped roots
Surflan on St. Augustinegrass pendimethalin on zoysiagrass Dimension on bermudagrass Swollen, club shaped roots


40 Asulam Asulox readily absorbed by foliage, minor root absorption
translocates in phloem and xylem inhibits cell division also inhibits RNA and protein synthesis used on St. Augustinegrass and ‘Tifway’ bermudagrass

41 Pronamide Kerb root absorbed, translocated in xylem
controls emerged cool-season grasses inhibits cell division Used only on warm-season turfgrasses

42 Cell Membranes Contain the cellular contents and regulate the entry and exit of substances that promote or inhibit plant metabolism

43 Diquat Reward LS contact, very rapidly absorbed,does not translocate
requires light for activity disrupts electron flow in photosynthesis leads to formation of free radicals which damages cell membranes cellular fluids leak, followed by death used on dormant bermudagrass

44 Glufosinate Finale readily absorbed by leaves
primarily 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 photosynthesis used on dormant bermudagrass

45 Cell Membrane Disrupters
Finale, Reward, Paraquat Finale on zoysia Damage occurs within hours. Membrane destruction. No redistribution Complete coverage for kill.

46 Organic Arsenicals MSMA, DSMA, CMA, CAMA foliage absorbed
Mobile in xylem and phloem Not well understood, rapid desiccation indicates cell membrane destruction Used on cool-season grasses, bermuda and zoysiagrass

47 Leaf burn on broadleaves and grasses with yellow leaf tips on grasses
Terminal yellowing of grasses MSMA on zoysia

48 MSMA injury on tall fescue

49 Tee infested with Texas sedge

50 Texas sedge tee after treatment with MSMA

51 Oxadiazon Ronstar all turfgrasses, except centipede
readily shoot absorbed, less so by roots can be foliage absorbed, “contact burn” does not significantly translocate Light required inhibits key enzyme in chlorophyll synthesis, toxic radicals formed, disrupts cell membranes

52 Oxadiazon (Ronstar) PRE
2G – Ky. Bluegrass, Bermuda, seashore paspalum, t. fescue, zoysia, St. Augustine 50WSP – bermuda, St. Augustine, zoysia Annual grasses, selected broadleaves

53 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

54 Carfentrazone QuickSilver Contact, quickly absorbed Fast-acting
Inhibits enzyme (protoporphyrinogen oxidase) in chlorophyll synthesis pathway. Leads to formation of toxic intermediates which disrupt cell membranes.

55 Carfentrazone Sold with phenoxy herbicides and dicamba as PowerZone and SpeedZone All turfgrasses does not significantly translocate

56 Sulfentrazone Dismiss Root and shoot absorbed Fast-acting
Inhibits enzyme (protoporphyrinogen oxidase) in chlorophyll synthesis pathway. Leads to formation of toxic intermediates which disrupt cell membranes.

57 Carfentrazone and Sulfentrazone
Carfentrazone – POST, all turfgrassses Sulfentrazone – PRE, although does have POST activity

58 Growth Regulation Naturally produced hormones (auxins, cytokinins, gibberellins, others) are involved in the regulation of normal growth and development.

59 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.

60 Growth Regulator Herbicides
Phenoxys 2,4-D, dichlorprop mecoprop, MCPA Benzoics Banvel, Vanquish Picolinic Acids Confront Turflon Lontrel SpotLight Quinolinecarboxylic Drive Trimec on bermuda

61 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

62 Quinclorac Drive shoot and root absorbed
readily translocates in xylem and phloem MOA not fully understood Broadleaf's - alters auxin levels Grasses - affects cell wall synthesis, increases cyanide and ethylene production Used on tall fescue, zoysia and bermudagrass, Ky bluegrass

63 Drive on crabgrass, 7 days after treatment

64 Phenoxy, Benzoic Acid, Picolinic Acid
Phenoxies – used on cool- and warm season turfgrasses, except St. Augustine Benzoic acids - used on cool- and warm season turfgrasses Lontrel – all cool- and warm-season grasses Confront – cool- and warm-season grasses, except St. Augustine Turflon – Ky. Bluegrass and tall fescue

65 Growth Regulator Herbicides
Symptomology 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.

66 2,4-D overdose on St. Augustinegrass

67 2,4-D Injury on Soybean

68 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

69 Growth Inhibitors Bensulide - Betasan, Pre-San Metolachor - Pennant
root absorbed, essentially no translocation disrupts cell division and enlargement Metolachor - Pennant mainly shoot absorbed, some root uptake translocates in xylem inhibit root and shoot growth disrupts protein, fatty acid and lipid synthesis

70 Growth Inhibitors Bensulide - Betasan, Pre-San Metolachor – Pennant
Cool- and warm-season turfgrasses Metolachor – Pennant Only on warm-season turfgrasses

71 Growth Inhibitors Siduron - Tupersan
readily absorbed by roots, translocated in xylem inhibits root growth, may disrupt mitosis Used only on cool-season turfgrasses and zoysiagrass

72 Growth Inhibitors Gallery
rapidly absorbed by roots, minimal foliage absorption moves in xylem inhibits cell wall biosynthesis Used on all cool- and warm-season turfgrasses

73 Fatty Acid Synthesis Fatty acids are important components of cell membranes Inhibition fatty acid synthesis blocks production of lipids needed for new cell growth.

74 Fatty Acid Inhibitors Cyclohexanediones
sethoxydim - Vantage, Poast used only on centipedegrass and fine fescue clethodim – Envoy used only on centipedegrass Rapidly absorbed by leaves, extensively translocated via phloem to meristems Inhibit key enzyme in fatty acid synthesis

75 Fatty Acid Inhibitors Aryl-oxy-phenoxies
fenoxaprop - Acclaim Extra fluazifop - Fusilade II diclofop - Illoxan Rapidly absorbed by leaves, extensively translocated via phloem to meristems, (diclofop translocation is slow) Inhibit key enzyme in fatty acid synthesis

76 Fatty Acid Inhibitors Aryl-oxy-phenoxies fenoxaprop - Acclaim Extra
used on cool-season grasses and zoysiagrass fluazifop - Fusilade II Used only on tall fescue and bermudagrass diclofop – Illoxan Used only on bermudagrass

77 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

78 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)

79 “rotted” meristem Source: W. K. Vencill, UGA

80 Turf Weed Management

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