Herbicide Families Section 6

Transcription

1 Herbicide Families Section 6

2 Chemical name: only one Herbicide Names** N-(phosphonomethyl)glycine Common name: only one glyphosate Trade names: can be multiple trade names by the same company or trade names by other companies Roundup PowerMax Monsanto Roundup Weathermax Monsanto Touchdown Hi-Tech Syngenta Durango Dow Glystar Albaugh ** not in your notes

3 What is Mode of Action? The biochemical mechanism by which a herbicide causes growth to cease in target plants. Target site is the exact location of inhibition. Example: inhibition of ALS (acetolactate synthase), an enzyme involved in synthesis of branched-chain amino acids.

4 Purpose of MOA Classification Systems Rotating MOA s and using mixtures of MOA s is a key component in herbicide resistance management strategies

5 MOA Inhibition of ACCase Inhibition of ALS Inhibition of PS II Inhibition of PS II Inhibition of PS II PS I electron diversion Inhibition of PPO Bleaching: inhibition of carotenoid biosynthesis at PDS Bleaching: inhibition of HPPD Bleaching: inhibition of carotenoid biosynthesis, unknown target Inhibition of EPSPS Inhibition of glutamine synthetase Microtubule assembly inhibition Inhibition of long-chain fatty acid synthesis Inhibition of cell wall synthesis Inhibition of lipid synthesis; not ACCase inhibition Synthetic auxins Inhibition of auxin transport Unknown

6 Purpose of MOA Classification Systems Rotating MOA s and using mixtures of MOA s is a key component in herbicide resistance management strategies A simple classification system helps the layperson

7 Two Classification Systems For Herbicide MOA 1. HRAC (Herbicide Resistance Action Committee) Use a letter system (see table 1 in notes) 2. WSSA (Weed Science Society of America) Use a number system

8 HRAC Code WSSA Code MOA A 1 Inhibition of ACCase B 2 Inhibition of ALS C1 5 Inhibition of PS II C2 7 Inhibition of PS II C3 6 Inhibition of PS II D 22 PS I electron diversion E 14 Inhibition of PPO F1 12 Bleaching: inhibition of carotenoid biosynthesis at PDS F2 27 Bleaching: inhibition of HPPD F3 13 Bleaching: inhibition of carotenoid biosynthesis, unknown target G 9 Inhibition of EPSPS H 10 Inhibition of glutamine synthetase K1 3 Microtubule assembly inhibition K3 15 Inhibition of long-chain fatty acid synthesis L 20 and 21 Inhibition of cell wall synthesis N 8 Inhibition of lipid synthesis; not ACCase inhibition O 4 Synthetic auxins P 19 Inhibition of auxin transport Z 17 Unknown

9 Purpose of MOA Classification Systems Rotating MOA s and using mixtures of MOA s is a key component in herbicide resistance management strategies A simple classification system helps the layperson Classification code required on labels in some countries; still optional in US Labels of newer products in US carry WSSA code

10

11 Canadian labels

12 US labels

13 Section 6 What do you need to know? The family names The highlighted material (hard to see highlighting on hard copy of notes; see online copy)

14 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients A 1 Inhibition of Aryloxyphenoxy- diclofop-methyl acetyl CoA propionates fenoxaprop-p-ethyl carboxylase (ACCase) fluazifop-p-butyl quizalofop-p-butyl

15 Basic structure of an aryloxyphenoxypropionate herbicide An ester of 4-oxyphenoxypropanoic acid

16 diclofop-methyl (Hoelon, Illoxan) fluazifop-p-ethyl (Fusilade DX, Fusilade II)

17 Aryloxyphenoxypropionate herbicides Mode of action: HRAC code A, WSSA code 1 Inhibit the enzyme acetyl-coa caryboxylase (ACCase). Block fatty acid biosynthesis; leads to inhibition of phospholipid synthesis; cell membrane formation is interrupted

18 Table 1. HRAC herbicide classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients A 1 Inhibition of Aryloxyphenoxy- diclofop-methyl acetyl CoA propionates fenoxaprop-p-ethyl carboxylase fluazifop-p-butyl (ACCase) quizalofop-p-butyl Commonly called fops

19 Characteristics of aryloxyphenoxypropionates Commonly called FOPs; commonly called POST graminicides Applied POST; diclofop also applied PRE Used to control grassy weeds; no activity on other monocots or dicots Very rapid absorption Symplastic translocation Short soil residual; little to no PRE activity except diclofop

20 Uses of Aryloxyphenoxypropionates A. Diclofop-methyl 1. Hoelon a. POST on wheat and barley for Italian ryegrass control b. PRE on wheat for Italian ryegrass control 2. Illoxan a. POST for goosegrass in established bermudagrass golf courses

21 Uses of Aryloxyphenoxypropionates B. Fenoxaprop-P-ethyl 1. Acclaim Extra a. POST in some turf species for crabgrass and goosegrass control and bermudagrass suppression 2. Packaged mixture a. Fusion (contains fluazifop-p-ethyl plus fenoxaprop-p-ethyl); POST for annual and perennial grass control in cotton and soybeans; not commonly used in NC

22 Uses of Aryloxyphenoxypropionates C. Fluazifop-P-butyl 1. Fusilade DX a. POST on cotton, soybeans, various fruit & nut trees, various vegetables 2. Fusilade II a. POST on various ornamentals b. POST in tall fescue and zoysiagrass

23 Two Trade Names of Same Active Ingredient Can they be used interchangeably? The label is the law (the label in your hand) Can only use a pesticide in accordance with its label (the label in your hand) Can only use on sites specifically covered on the label (the label in your hand)

24 Uses of Aryloxyphenoxypropionates C. Fluazifop-P-butyl 1. Fusilade DX (2 lb/gal fluazifop-p-butyl) a. POST on cotton, soybeans, various fruit & nut trees, various vegetables 2. Fusilade II (2 lb/gal fluazifop-p-butyl) a. POST on various ornamentals b. POST in tall fescue and zoysiagrass Fusilade DX on ornamentals = label violation

25 Uses of Aryloxyphenoxypropionates D. Quizalofop-P-ethyl 1. Assure II a. POST on cotton, soybeans for annual and perennial grass control b. POST on dry beans, dry and succulent peas, lentils, and snapbeans

26 Table 1. HRAC herbicide classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients A 1 Inhibition of Cyclohexane- clethodim acetyl CoA diones sethoxydim carboxylase (ACCase)

27 Basic structure of a cyclohexanedione O R R OH Consists of cyclohexene, oxygen at position 1, hydroxyl group at position 3, and substitutions at positions 2 and 5.

28 Clethodim (Select, Envoy) Sethoxydim (Poast, Poast Plus, Vantage

29 Cyclohexanedione herbicides Mechanism of action: HRAC code A, WSSA code 1 Inhibit the enzyme acetyl-coa caryboxylase (ACCase). Blocks fatty acid biosynthesis; leads to inhibition of phospholipid synthesis; cell membrane formation is interrupted

30 Table 1. HRAC herbicide classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients A 1 Inhibition of Cyclohexane- clethodim acetyl CoA diones sethoxydim carboxylase (ACCase) Commonly called DIMs)

31 Characteristics of aryloxyphenoxypropionates Commonly called DIMs; commonly called POST graminicides Applied POST only Used to control grassy weeds; no activity on other monocots or dicots Very rapid absorption Symplastic translocation Very short soil residual; little to no PRE activity

32 Uses of Cyclohexanediones A. Clethodim 1. Select (2 EC) and Select Max (0.97 EC) a. POST on cotton, peanut, soybean, and several other agronomic dicots b. POST on many vegetables 2. Envoy a. POST on centipedegrass, conifers, numerous ornamentals, non-bearing fruit crops

33 Uses of Cyclohexanediones B. Sethoxydim 1. Poast Plus (1 EC) a. POST on cotton, peanut, soybean, alfalfa, and clover for annual and perennial grass control 2. Poast (1.5 EC) a. Same uses as Poast Plus, and tobacco 3. Vantage (1 EC) a. POST on numerous ornamental, nursery, and tree crops and non-bearing fruit trees b. POST on centipedegrass and fine fescue

34 Table 1. HRAC herbicide classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients A 1 Inhibition of Phenylpyrazolines pinoxaden acetyl CoA carboxylase (ACCase) Sometimes called the DENs

35 Uses of Phenylpyrazolines A. pinoxaden 1. Axial (0.42 EC) a. POST on wheat and barley for grassy weeds; primarily Italian ryegrass in NC

36 Sethoxydim drift Univ. Wisconsin

37 ACCase Inhibitors A. York, NCSU A. York, NCSU

38 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients B 2 Inhibition of Sulfonylureas acetolactate synthase (ALS) chlorimuron-ethyl chlorsulfuron foramsulfuron halosulfuron-methyl iodosulfuron mesosulfuron metsulfuron-methyl nicosulfuron primisulfuron-methyl prosulfuron rimsulfuron sulfometuron sulflosulfuron thifensulfuron-methyl tribenuron-methyl trifloxysulfuron

39 Basic structure of a sulfonylurea O H O H R - S - N - C - N - R O Consist of sulfonylurea nucleus (in yellow) with various substitutions (R)

40 Chlorimuron-ethyl (Classic) Foramsulfuron (Option)

41 Sulfonylurea herbicides Mechanism of action: HRAC code B; WSSA code 2 Inhibit the enzyme acetolactate synthase (ALS) Inhibit synthesis of essential amino acids valine, leucine, and isoleucine

42 Characteristics of Sulfonylureas Commonly called SUs High unit activity Symptoms develop slowly Applied PRE or POST, depending upon particular product; some used PRE and POST Control grasses, sedges, broadleaf weeds; spectrum varies considerably among various SUs Symplastic and apoplastic translocation Soil persistence varies greatly among SUs; persistence is ph-dependent; longer persistence at higher ph values; rotational restrictions common

43 Uses of Sulfonylureas A. Chlorimuron 1. Classic a. POST on soybean, broadleaf weeds b. Late POST on peanut only for Florida beggarweed; peanuts must be > 60 days old

44 Uses of Sulfonylureas A. Chlorimuron 2. Packaged mixture a. Canopy (chlorimuron + metribuzin) i. PPI/PRE on soybean, broadleaf weeds

45 Uses of Sulfonylureas B. Chlorsulfuron 1. Glean a. PRE and POST on small grains in Plains states for broadleaf weeds; not used in eastern US due to very long persistence 2. Corsair a. POST on warm-season turf species for broadleaf weeds, wild garlic, ryegrass, and tall fescue control

46 Add to your notes! Uses of Sulfonylureas B. Chlorsulfuron 3. Finesse (premix of chlorsulfuron + metsulfuron) PRE or POST in wheat, primarily for broadleaf weeds. Applied PRE, it suppresses some annual grasses. Used PRE in NC for Italian ryegrass suppression. Must double-crop with STS soybeans.

47 C. Foramsulfuron Uses of Sulfonylureas 1. Option a. POST on corn for annual and perennial grasses and selected broadleaf weeds; formulated with a safener 2. Revolver a. POST control of annual bluegrass, overseeded ryegrass, and tall fescue in bermudagrass and zoysiagrass

48 Uses of Sulfonylureas D. Halosulfuron-methyl 1. Permit (currently not registered in eastern US) a. POST on corn and sorghum for nutsedge species and selected broadleaf weeds b. Under hooded sprayer on cotton; not used in US 2. Sandea a. POST on various vegetable crops

49 Uses of Sulfonylureas D. Halosulfuron-methyl 3. Sempra a. POST on corn and sorghum for nutsedge species and selected broadleaf weeds b. POST on established turfgrasses 4. Sempra CA a. Same uses as Sempra plus tree nuts

50 Uses of Sulfonylureas D. Halosulfuron-methyl 5. Manage a. POST on established warm- and cool-season turf, ornamental turf, and landscaped areas, primarily for nutsedge control

51 Uses of Sulfonylureas E. Iodosulfuron a. Registered for small grains in Europe b. Not registered alone for any uses in U.S. c. Equip is packaged mixture of iodosulfuron plus foramsulfuron; POST application to corn to control grasses and broadleaf weeds; not commonly used in NC

52 Uses of Sulfonylureas F. Mesosulfuron a. Osprey (4.5 WDG) 1. POST control of Italian ryegrass (and selected other grasses) in wheat; widely used in NC

53 Uses of Sulfonylureas G. Metsulfuron-methyl 1. Cimarron 60 WDG (formerly Ally) a. POST broadleaf control in wheat, barley, triticale; not used in NC because of persistence b. POST broadleaf control in grain sorghum (western US only) c. POST application in pastures for broadleaf control (widely used in NC); and to remove bahiagrass from established bermudagrass

54 G. Metsulfuron-methyl 2. Cimarron Max Uses of Sulfonylureas a. Co-pack of metsulfuron and a mixture of dicamba and 2,4-D b. Used POST in perennial grasses grown for hay or pasture 3. Manor a. POST control of broadleaf weeds in turf

55 Uses of Sulfonylureas H. Nicosulfuron 1. Accent a. POST on corn for annual grasses, johnsongrass, and some broadleaves 2. Packaged mixtures a. Steadfast (nicosulfuron + rimsulfuron): POST on corn for annual grasses, johnsongrass, broadleaf weeds b. Steadfast ATZ (nicosulfuron + rimsulfuron + atrazine): POST on corn c. Stout (nicosulfuron + thifensulfuron): POST on corn; this one not in your notes

56 Uses of Sulfonylureas I. Primisulfuron 1. Beacon a. POST on corn for annual grasses, johnsongrass, and some broadleaves; once widely used in NC; not sold alone now

57 Uses of Sulfonylureas J. Prosulfuron 1. Peak a. POST on grain sorghum for broadleaves b. POST on small grains for broadleaf weeds and wild garlic; not used in NC due to rotational restrictions on double-crop soybeans 2. Packaged mixtures a. Spirit (prosulfuron + primisulfuron); POST on corn for broadleaf weeds

58 Uses of Sulfonylureas K. Rimsulfuron 1. Matrix a. PRE and POST on potatoes for broadleaf weeds 2. Resolve a. PRE and POST in corn to control selected annual grasses and broadleaf weeds; limited spectrum of control; primarily mixed with glyphosate for burndown or for POST on Roundup Ready corn

59 Uses of Sulfonylureas K. Rimsulfuron 1. Matrix a. PRE and POST on potatoes for broadleaf weeds 2. Resolve a. PRE and POST in corn 3. Resolve Q (premix of rimsulfuron + thifensulfuron + safener); POST in corn

60 Uses of Sulfonylureas K. Rimsulfuron 3. TransXit a. POST on warm-season turfgrasses; i. For annual bluegrass & perennial ryegrass in bermudagrass ii. For tall fescue and certain broadleaf weeds in centipedegrass and zoysiagrass

61 Uses of Sulfonylureas L. Sulfometuron-methyl 1. Oust a. POST for weed control in bermudagrass and centipedegrass turf; bahiagrass release in unimproved turf (roadsides) b. Various forestry and non-cropland uses

62 Uses of Sulfonylureas L. Sulfosulfuron 1. Certainty Turf Herbicide a. POST control of sedges and tall fescue in bermudagrass, centipedegrass, zoysiagrass, or St. Augustinegrass b. Annual bluegrass control in actively growing bermudagrass 2. Outrider a. POST on several broadleaf and grassy weeds on roadsides, rights-of-way, and other non-crop sites. Particularly effective on johnsongrass

63 Uses of Sulfonylureas M. Thifensulfuron-methyl 1. Harmony SG a. POST on wheat, barley, oats, triticale for broadleaf weeds b. POST on soybean for broadleaf weeds 2. Packaged mixtures a. Harmony Extra (thifensulfuron-methyl + tribenuron-methyl); POST on wheat, barley, oats, triticale for broadleaf weeds and wild garlic; widely used in NC

64 Uses of Sulfonylureas N. Thibenuron-methyl 1. Express a. POST on wheat, barley, triticale for broadleaf weeds; not used in NC

65 Uses of Sulfonylureas O. Trifloxysulfuron 1. Envoke a. POST and POST-directed on cotton for broadleaf weeds and nutsedge 2. Monument a. POST control of broadleaf weeds and nutsedge in turf

66 Whew! That s the end of the sulfonylureas. But, it is not the end of the ALS inhibitors.

67 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients B 2 Inhibition of Imidazolinones imazamox acetolactate imazapic synthase imazapyr (ALS) imazaquin imazethapyr

68 Basic structure of an imidazolinone R C N C CH 3 CH CH 3 H N C O CH 3 Consists of imidazole ring with methyl and isopropyl radicals at 4-position, oxygen at 5-position, and either a pyridine or a quinoline ring attached to 2- position.

69 Imazapic ammonium salt (Cadre, Plateau) Imazaquin ammonium salt (Scepter, Image)

70 Imidazolinone herbicides Mechanism of action: HRAC code B; WSSA code 2 Inhibit the enzyme acetolactate synthase (ALS). Inhibit synthesis of essential amino acids valine, leucine, and isoleucine

71 Characteristics of Imidazolinones Commonly called IMIs Applied PPI/PRE or POST, depending upon particular product; some used PRE and POST Primarily control broadleaf weeds; most IMIs have activity on grasses and sedges Symplastic and apoplastic translocation Slow activity Soil persistence varies among IMIs; except for imazamox, IMIs have long persistence; rotational restrictions are common; mainly microbial degradation IMI-resistant, non-transgenic corn and wheat are available; Clearfield tradename; resistance due to a less sensitive ALS

72 Uses of Imidazolinones A. Imazamox ammonium salt 1. Beyond a. POST on Clearfield wheat for certain annual grasses and broadleaf weeds; main use in NC will be for Italian ryegrass 2. Raptor a. POST on soybean, alfalfa, English peas, snap beans, and edible legumes to control grasses and broadleaf weeds; very little used in NC

73 Uses of Imidazolinones B. Imazapic ammonium salt 1. Cadre a. POST on peanut for broadleaf weeds and nutsedge; also some grass activity; rotational restriction for cotton 2. Plateau a. PRE or POST on wildflowers b. POST on centipedegrass to control sedges, bahiagrass, and crabgrass c. POST on turf on rights-of-way, industrial turf, and recreational turf

74 Uses of Imidazolinones C. Imazapyr isopropylamine salt 1. Arsenal, Chopper a. Forestry uses 2. Packaged mixtures a. Lightning (imazethapyr + imazapyr); POST on Clearfield corn for broadleaf and grass control

75 Uses of Imidazolinones D. Imazaquin ammonium salt 1. Scepter a. PPI, PRE, POST on soybean for broadleaf weeds; rotational restriction for cotton 2. Image a. POST in established warm-season turfgrasses for broadleaf weeds, wild garlic, sedges, field sandbur, and overseeded perennial ryegrass b. Can be used on numerous established ornamentals

76 Uses of Imidazolinones E. Imazethapyr ammonium salt 1. Pursuit a. POST on alfalfa for broadleaf weeds and grass suppression b. PPI, PRE, POST on peanut, soybean, Clearfield corn for broadleaf weeds and suppression of annual grasses and nutsedge

77 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients B 2 Inhibition of Triazolo- cloransulam-methyl acetolactate pyrimidines diclosulam synthase flumetsulam (ALS) pyroxsulam

78 Basic structure of a triazolopyrimidine R O R = = - NH - S - O N N N R N R Consists of sulfanilide (in yellow), triazolopyrimidine ring (5- member ring with three N s, and a pyrimidine ring (6-member ring with two N s)

79 Cloransulam-methyl (FirstRate) Diclosulam (Strongarm) Flumetsulam (Python)

80 Triazolopyrimidine herbicides Mechanism of action: HRAC code B; WSSA code 2 Inhibit the enzyme acetolactate synthase (ALS) Inhibit synthesis of essential amino acids valine, leucine, and isoleucine

81 Characteristics of Triazolopyrimidines Applied PRE or POST, depending upon particular product; some used PRE and POST Primarily control broadleaf weeds Symplastic and apoplastic translocation Relatively persistent; longer persistence at lower ph levels; significant rotational restrictions for NC crops diclosulam: 18 months for corn, tobacco, grain sorghum flumetsulam: 18 months for cotton

82 Uses of Triazolopyrimidines A. Cloransulam-methyl 1. FirstRate a. PPI, PRE, POST on soybean for broadleaf weeds; used only POST in NC 2. Co-packaged mixture a. Frontrow (cloransulam + flumetsulam); POST on soybean for broadleaf weeds; not used in NC b. Gangster (premix of cloransulam and flumioxazin); early preplant or PRE for broadleaf control in soybean; not much used to date in NC

83 Uses of Triazolopyrimidines B. Diclosulam 1. Strongarm a. PPI, PRE, and ground cracking on peanut for broadleaf weeds; also controls some weeds POST, but currently no label for POST

84 Uses of Triazolopyrimidines C. Flumetsulam 1. Python a. PPI or PRE on corn and soybean for broadleaf weeds; seldom used on soybean in NC; essentially never used on corn due to corn injury

85 D. pyroxsulam Uses of Triazolopyrimidines 1. Powerflex a. POST in wheat for grassy weeds; new, no commercial use in 2008

86 No Registered Uses for Triazolopyrimidines in Turf or Horticultural Crops

87 Table 1. HRAC herbicide classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients B 2 Inhibition of Pyrimidinyl pyrithiobac acetolactate thiobenzoates bispyribac synthase (ALS)

88 Basic structure of a pyrimidinyl thiobenzoate O C - OH N - S - N Consists of benzoic acid (left) and pyrimidine (right) with a sulfur (thio) bridge

89 Pyrithiobac sodium salt (Staple)

90 Pyrimidinyl thiobenzoates herbicides Mechanism of action: HRAC code B; WSSA code 2 Inhibit the enzyme acetolactate synthase (ALS) Inhibit synthesis of essential amino acids valine, leucine, and isoleucine

91 Pyrimidinyl thiobenzoate herbicides 1.Pyrithiobac (Staple) 2.Bispyribac (Velocity)

92 Characteristics and Uses of Pyrithiobac (a pyrimidinyl thiobenzoate) Trade name Staple LX Cotton is only registered use; applied PRE or POST in cotton, primarily for broadleaf weeds; suppresses nutsedge Symplastic and apoplastic translocation Symptoms develop slowly Relatively long persistence, but only agronomic crop with carryover concerns is sorghum

93 Uses of bispyribac (a pyrimidinyl thiobenzoate) Trade name Velocity Seedhead suppression of annual bluegrass in overseeded bermudagrass fairways and tees

94 Symptoms of ALS Inhibitors

95 Imidazolinone

96 Pyrithiobac A.York, NCSU Trifloxysulfuron S. Stewart, LSU ALS Inhibitors Primisulfuron + prosulfuron A.York, NCSU

97 Stunting by trifloxysulfuron applied S. Stewart, LSU postemergence A. York, NCSU

98 Imazaquin carryover A. York, NCSU A. York, NCSU

99 Corn roots imazaquin carryover York, NCSU

100 ALS Inhibitors Postemergence Imazethapyr, A. York, NCSU Chloransulam, A. York, NCSU Imazethapyr, A. York, NCSU

101 ALS Inhibitors postemergence Chlorimuron, A. York, NCSU Pyrithiobac, A. York, NCSU

102 Leaf crinkling by nicosulfuron Univ. Wisconsin Ear pinching by nicosulfuron Purdue Univ.

103 Leaf distortion by chlorimuron A. York, NCSU A. York, NCSU

104 Chlorsulfuron + metsulfuron carryover T. Pegram, NCSU

105 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients C1 5 Inhibition of Triazines ametryne photosynthesis atrazine at photosystem prometryn II simazine

106 Basic structure of a triazine R N N R N R Six-membered ring with two or more N s is an azine. If three N s in ring, it is a triazine. If N s arranged symmetrically, it is a s-triazine.

107 Substitutions on 2-position of the triazine ring Chloro-s-triazine Methoxy-s-triazine Methylthio-s-triazine Cl O CH 3 S CH 3 N N N N N N N N N N N N N N N

108 Atrazine a chloro-s-triazine Prometryn a methylthio-s-triazine

109 Mode of action of Triazine Herbicides Inhibit electron flow in photosystem II of the light reaction of photosynthesis. Require light for phytotoxicity. Death too rapid to be explained by starvation. Production of free radical, resulting from blocking normal function of photosystem II, is likely responsible for rapid plant kill.

110 Characteristics of Triazines Absorbed by roots and foliage. Applied PRE, POST, or PRE and POST, depending upon particular herbicide. Apoplastically translocated. When soil applied, symptom is chlorosis between veins and around leaf margins of larger, lower leaves. Followed by necrosis. Relatively persistent. Average half-life 60 days, but varies greatly. Normal rates applied properly seldom create carryover problem in NC.

111 Uses of Triazines A. Ametryn 1. Evik a. POST-directed (layby) on corn > 12 inches tall. Broadleaf weeds and grasses. Do not apply within 3 weeks of tasseling.

112 B. Atrazine Uses of Triazines 1. AAtrex and generic brands a. PPI, PRE, or POST on corn and grain sorghum, primarily for broadleaf weeds. Also kills some species of annual grasses, but not fall panicum, broadleaf signalgrass, or Texas panicum. Has been found in ground and surface water.

113 Uses of Triazines B. Atrazine 1. AAtrex (4 F) and Purge (2 F) a. Registered for centipedegrass, St. Augustinegrass, and dormant bermudagrass. Applied in late fall to control annual bluegrass and winter annual weeds

114 Uses of Triazines 2. Packaged mixtures containing atrazine for PPI, PRE, or early POST use in corn; some also registered for sorghum: a. atrazine + acetochlor Degree Xtra, FulTime, Harness Xtra b. atrazine + alachlor Bullet, Lariat c. atrazine + dimethenamid-p Guardsman Max d. atrazine + s-metolachlor Bicep II Magnum

115 Uses of Triazines 3. Prepackaged mixtures containing atrazine for POST use in corn a. atrazine + nicosulfuron + rimsulfuron Steadfast ATZ b. atrazine + glufosinate-ammonium Liberty ATZ (LL corn only)

116 C. Prometryn 1. Caparol Uses of Triazines a. PRE and POST-directed in cotton, primarily for broadleaf weeds. Generally not used PRE in NC, but commonly used POST-directed in in combination with MSMA or glyphosate.

117 Uses of Triazines D. Simazine 1. Princep and generic brands a. PPI and PRE in corn. Commonly mixed with atrazine. Combination of simazine + atrazine suppresses or controls fall panicum. b. Registered for orchard floor application in a number of fruit and nut crops and vineyards. c. Preemergence in 2+-year old Christmas trees

118 Uses of Triazines D. Simazine 2. Princep and Regal Wynstar a. Late fall application to bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass for PRE control of annual bluegrass and winter annual broadleaf weeds

119 Table 1. HRAC herbicide classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients C1 5 Inhibition of Triazinones metribuzin photosynthesis (formerly called hexazinone at photosystem as-triazines) II

120 metribuzin O CH 3 H 3 C - C CH 3 N NH 2 N N S CH 3

121 Metribuzin Mode of action, translocation patterns, and injury symptoms same as for triazines. 30- to 60-day soil half-life; no carryover problems in NC.

122 1. Sencor Uses of Metribuzin a. PPI, PRE on soybeans, primarily for broadleaf weeds. Never widely used in NC; marginally effective on cocklebur and morningglory. Narrow margin of tolerance on soybean; injury concerns on light or variable soils. Varietal differences in tolerance. Lexone, no longer on market, had same crop uses as Sencor.

123 1. Sencor Uses of Metribuzin b. POST-directed on soybeans > 8 inches tall, primarily for broadleaf weeds. Never widely used in NC, but can be an excellent component of a herbicide program.

124 1. Sencor Uses of Metribuzin c. POST and POST-directed on corn; not used in NC. d. POST to dormant alfalfa. e. POST and wheat and barley; not used in southeastern US. Also, not labeled in NC. f. Registered for use on several vegetable crops. Of greatest importance in NC is use PRE and POST on potatoes.

125 2. Packaged mixtures Uses of Metribuzin a. Axiom (metribuzin + flufenacet) ii. i. Contains low rate of metribuzin. PPI and PRE on corn and soybeans for annual grasses and small-seeded broadleaf weeds. Seldom used in NC. Section 18 Emergency Exemption in NC and other southeastern states in fall of 2002 and 2003 to control Hoelonresistant Italian ryegrass in wheat. 24c registration in 2007.

126 Uses of Metribuzin 2. Prepackaged mixtures b. Canopy (metribuzin + chlorimuron) i. PPI or PRE on soybeans for broadleaf control. Fair amount used in NC. Same tolerance concerns as Sencor. c. Boundary (metribuzn + s-metolachlor) i. PPI and PRE on soybeans for annual grasses and broadleaf weeds; not used in NC.

127 Uses of Metribuzin 3. Sencor 75 Turf Herbicide a. For use on established bermudagrass which has mowing height 0.5 inches or greater. For control of crabgrass, goosegrass, and annual broadleaf weeds. Higher rates can be applied to dormant bermudagrass.

128 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients C1 5 Inhibition of Uracils terbacil photosynthesis at photosystem II

129 Terbacil Same mode of action as triazines Root absorbed, apoplastically translocated Not absorbed well by foliage Long persistence

130 Uses of terbacil 1. Sinbar a. Registered on certain horticultural crops for control of broadleaf weeds and certain annual grasses. b. Primary use in NC is application to orchard floor in apple and peach orchards, usually mixed with diuron. c. Other uses include strawberries, blueberries, and asparagus.

131 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients C1 5 Inhibition of Triazines photosynthesis Triazinones at photosystem Uracils II

132 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients C2 7 Inhibition of Ureas diuron photosynthesis fluometuron at photosystem linuron II siduron

133 Urea fertilizer H O H N C N H H

134 Structure of Urea Herbicide R O R N C N R R

135 Diuron Fluometuron Linuron Siduron

136 Mode of action of Urea Herbicides Inhibit electron flow in photosystem II of the light reaction of photosynthesis. Different binding behavior to protein D 1 than triazines, hence in a different MOA group. No cross resistance. Require light for phytotoxicity. Death too rapid to be explained by starvation. Production of free radical, resulting from blocking normal function of photosystem II, is likely responsible for rapid plant kill.

137 Characteristics of Urea Herbicides Applied PRE and POST; absorbed by roots and foliage. Apoplastic translocation Symptoms very similar to triazines Relatively long half-lives. Linuron carryover has been no concern. Fluometuron carryover occasionally observed, but usually associated with misapplication. Diuron could carry over to tobacco and veggies

138 1. Diuron Uses of Urea Herbicides a. Direx, Karmex i. PRE and POST-directed in cotton; ii. PRE in newly sprigged bermudagrass pastures iii. POST in established alfalfa, early spring iv. POST to soil under various tree fruit and nut crops

139 2. Fluometuron Uses of Urea Herbicides a. Cotoran and generic names i. PRI, PRE, POST, and POST-directed in cotton, primarily for broadleaf weeds. Once widely used PRE in NC; less use when RR cotton came on market.

140 3. Linuron Uses of Urea Herbicides a. Linex, and generics i. PRE and POST-directed in soybean; once widely used PRE in NC, but almost none now used PRE. Controlled smallseeded broadleaf weeds. Never widely used as POST-directed, but an excellent component of soybean herbicide program. ii. PRE and POST-directed in corn; never used PRE in NC; some use POST-directed

141 Uses of Urea Herbicides 3. Linuron a. Linex, and generics iii. POST-directed in cotton, usually mixed with MSMA or diuron; primarily for broadleaf weeds. iv. PRE in potatoes v. PRE and POST in asparagus

142 Uses of Urea Herbicides 4. Siduron a. Tupersan i. PRE control of crabgrass and other annual grasses in bluegrass, fescue, perennial ryegrass, certain bentgrasses, and zoysiagrass.

143 Triazines, triazinones, uracils, and ureas are mobile photosynthesis inhibitors. Injury symptoms of these families are very similar.

144 Triazines and Ureas Atrazine carryover, NCSU Fluometuron preemergence, A. York, NCSU

145 Kansas State Univ. Metribuzin preemergence

146 Metribuzin preemergence A. York, NCSU

147 Triazines Metribuzin, New Brunswick Dept. Ag., Fisheries, and Aquaculture Simazine, New Brunswick Dept. Ag., Fisheries, and Aquaculture

148 Triazines and Ureas Atrazine-contaminated fumigant, A. York, NCSU Atrazine-contaminated fumigant, A. York, NCSU Fluometuron carryover, A. York, NCSU Fluometuron preemergence, A. York, NCSU

149 Fluometuron postemergence, cotton S. Culpepper, UGA

150 Triazine postemergence S. Culpepper, UGA

151 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients C1 5 Inhibition of Triazines photosynthesis Triazinones at photosystem Uracils C2 7 II Ureas C3 6 Nitriles

152 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients C3 6 Inhibition of Nitriles bromoxynil photosynthesis at photosystem II

153 Basic structure of a nitrile herbicide C N Phenyl ring with a nitrile group bonded at 1-position.

154 Bromoxynil octanoate ester O O-C-CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 2 -CH 3 Br Br C N

155 Mode of action of Nitrile Herbicides Inhibit electron flow in photosystem II of the light reaction of photosynthesis. Different binding behavior to protein D 1 than triazines, hence in a different MOA group. No cross resistance. Require light for phytotoxicity. Death too rapid to be explained by starvation. Production of free radical, resulting from blocking normal function of photosystem II, is likely responsible for rapid plant kill.

156 Characteristics of Bromoxynil Applied POST only Foliar absorbed, very little translocation. Little to no soil activity. Effective only on broadleaf weeds Symptoms are chlorotic blotches, followed by necrosis

157 Uses of Bromoxynil 1. Buctril a. POST on BXN cotton; controls broadleaf weeds; at rates used, effective on most broadleaf weeds; Amaranthus species and sicklepod are weaknesses; BXN cotton was commercial from 1996 to b. POST on corn, sorghum, and small grains for broadleaf weeds; seldom used in NC; does not fit our weed spectrum as well as alternative herbicides

158 Table 1. Herbicide MOA classification system. HRAC WSSA group group Mode of action Chemical family Active ingredients C3 6 Inhibition of Nitriles bromoxynil photosynthesis at photosystem II Benzothiadi- bentazon azinones

159 Bentazon Bentazon sodium salt

160 Mode of action of Bentazon Inhibit electron flow in photosystem II of the light reaction of photosynthesis. Different binding behavior to protein D 1 than C1 or C2 herbicides. Hence, it is in a different MOA subgroup. No cross resistance. Require light for phytotoxicity. Death too rapid to be explained by starvation. Production of free radical, resulting from blocking normal function of photosystem II, is likely responsible for rapid plant kill.

161 Characteristics of Bentazon Little to no soil activity; applied POST. Foliar absorbed, very little translocation. Effective on broadleaf weeds and some sedge species. Symptoms are chlorotic blotches, followed by necrosis.

162 1. Basagran Uses of Bentazon a. POST on peanut, soybean, corn, and sorghum. Commonly used on peanut, alone or in mixtures; was once commonly used on soybean; seldom used on corn and sorghum. b. POST on dry and succulent beans and peas. 2. Basagran T/O a. POST in most turf grass species; for control of annual broadleaf weeds and sedges

163 Bentazon Packaged Mixtures 1. Storm (bentazon + acifluorfen) a. POST on peanut and soybean. 2. Prompt (bentazon + atrazine) a. POST on established warm-season turfgrasses

164 Triazines, triazinones, uracils, and ureas are mobile photosystem II inhibitors. Nitriles and benzothiadiazinones are non-mobile photosystem II inhibitors.

165 Bromoxynil

166 Bromoxynil

167 Bentazon

168 Table 1. Herbicide MOA classification system. HRAC, WSSA Chemical Mode of action group family Active ingredients Inhibition of C1, 5 Triazines ametryn, atrazine, prometryn, simazine photosynthesis Triazinones metribuzin at photosystem Uracils terbacil II C2, 7 Ureas diuron, fluometuron, linuron, siduron C3, 6 Nitriles bromoxynil Benzothia- bentazon diazinones Photosystem I D, 14 Bipyridyliums diquat, paraquat electron diversion

169 Diquat dibromide salt Paraquat dichloride salt

170 Mode of action of Bipyridyliums Electron diversion in Photosystem I. Accept electrons from Photosystem II, then through a multi-step series of reactions, produces free radicals that destroy cell membranes. Light is required for activity. Causes rapid tissue desiccation.

171 Characteristics of Bipyridyliums Rapidly absorbed by foliage; short rain-free period. Potentially can translocate apoplastically, but tissue death occurs rapidly and this limits translocation; generally thought of as being non-mobile in plants. Late-day application can enhance activity. No soil activity; bound to soil very tightly (irreversibly bound to CEC)

172 Toxicity of Bipyridyliums Paraquat is highly toxic; label carries skull and crossbones Gramoxone Max formulated with stence agent and emetic Gramoxone Inteon formulated with emetic, purgative, and alginate that prevents absorption by body Diquat much less toxic; label has signal word Warning Diquat is in certain homeowner products

173 1. Paraquat Uses of Bipyridyliums a. Gramoxone Max, Gramoxone Inteon, Parazone, Firestorm i. Burndown in no-till systems ii. PRE before crop emergence to control emerged weeds iii. POST-directed in corn, sorghum, and and soybean; risky to crop; not used in NC. iv. Under hood in cotton v. POST to dormant alfalfa and between cuttings vi. Ground-cracking and POST in peanut vii. Harvest aid in several crops viii. Pasture and turf renovation ix. POST to weeds with no crop contact in tree and vine crops

174 1. Diquat Uses of Bipyridyliums a. Reward Landscape and Aquatic Herbicide i. Aquatic weed control ii. General weed control in number of noncrop and greenhouse situations iii. Turf renovation iv. Weed control in dormant, established bermudagrass and zoysiagrass (not recommended in NC)

175 Uses of Bipyridyliums 2. Packaged Mixtures a. QuickPRO i. Mixture of diquat and glyphosate a. POST to dormant bermudagrass or bahiagrass to control annual bluegrass and tall fescue

176 Paraquat drift A. York, NCSU

177 Paraquat

178 Paraquat directed