Final Exam Flashcards

Question

Type of Formulation Emulsifiable Concentrate (E or EC)

Answer 1

Active Ingredient not water soluble, soluble in **nonpolar solvents** **Can penetrate** the cuticle of the plant easier than water soluble Problems with **drift** at **high** (\> 80F) **temperatures** Plant wax is nonpolar making the herbicide easy to get into the plant

Answer 2

Dispersing agents (Enhances the dispersal of a power in a solid-liquid suspension) Thickener (used to reduce the number of fine droplets from a nozzle)

Answer 3

Compatibility Agents - Used to keep different types of formulations in suspension Antifoam Agents - To reduce foaming in the tank Emulsifiers - Material that aids in the suspension of fine drops of one liquid in another, like oil in water

Answer 4

Only some plants of a mixed population are injured

Answer 5

All plants of a mixed population are killed (paraquat and Roundup)

Answer 6

No movement in plant Kills **only** the **tissue** that is treated **Complete coverage** of the plant is needed to get good control (best applied when plant is **small**) Examples - aciflorfen (Blazer) (soybean) - bentazon (Basagran) (soybean & corn) - paraquat (Paraquat) (orchards & other places)

Answer 7

Moves in the plant from the **site of application** to other plant parts _Two Types of Movement_ - Symplastic (phloem) Moves with the **sugars**/typically moves to the **newest areas** of the plant - Apoplastic (xylem) Water moves in the **xylem**/going to the **oldest tissue** in the plant/applying to leaf it moves to the **outer edges** of the leaf

Answer 8

Herbicide moves in the **phloem** Moved with **sugars** Moved to the **YOUNGEST** tissue were demand for energy **greatest** Injury seen in youngest leaves and in the youngest roots Good for control of **perennials**

Answer 9

Herbicides that move in the **apoplast** move in the **xylem** Move with Water - Move to the **oldest**, most actively transpiring tissue If taken up by **roots** move to the **oldest** leaves If taken up by **leaves** stays in the **treated** leaf

Answer 10

Trizines (atrazine, metribuzin) Uracils (diuron, monuron)

Answer 11

Often done to control many types of weeds (mix broadleaf and grass herbicides) To have the operation be 'one pass' (to lessen application costs) To get synergistic responses (better kill) To lessen the costs of the 'expensive' herbicide by adding a cheaper tank mix partner

Answer 12

Sold by the Manufacturer - These already have what the manufacturer thinks is the best combination of ingredients - A premix may have similar active ingredients at different concentrations and be marketed under different names Examples Storm (29% bentazon + 18% acifluorfen) vs Galaxy (33% bentazon + 7% acifluorfen)

Answer 13

Mixed in the field **not** as the formulation - Caution must be taken - Incompatible Formulations The solution turns into **sludge** Having AI precipitate out of solution Mixing chemicals bound to clay with chemicals that are adsorbed by clay (i.e. glyphosate and DF formulations) Combining antagonistic chemicals (get no or little plant response) Getting too high a response (Burn crop or residual lasts too long) Not understanding all the ingredients already in a formulation When mixed there can be 4 types of responses that occur

Answer 14

When the response of a plant to each herbicide alone or in the mix is the same

Answer 15

When mixing 2 chemicals get a greater response than either chemical alone - This can be good if get better weed control i.e. mix a some 2,4-D (cheap) with Tordon (expensive) and get a more phytotoxicity than either alone - Bad if get more crop injury

Answer 16

When the mixture of 2 or more herbicides results in **less** than expected response (i.e. less weed control) than when any of them are used **separately** - If you mix 2,4-D with some wild oat herbicides get no wild oat control _Graph Info_ To get the same response as if the two chemicals were used alone, 1.2 to 1.5 times as much of either herbicide needes to be applied in the mix

Answer 17

Mix a nonphytotoxic adjuvant (i.e. crop oil or other) with a herbicide and get a response that is greater than the herbicide is used **alone** - Phytotoxicity increased usually results from **increased** leaf absorption - May reduce crop selectivity (may get more injury such as burned leaves or stunted plants)

Answer 18

Precise biochemical reaction that creates the herbicide's ultimate effect

Answer 19

Sequence of events that occur from the herbicides contact with the plant until its final effect is expressed

Answer 20

Precise enzyme or target area affected by the herbicide

Answer 21

2,4-D Dicamba Picloram

Answer 22

Trifluralin

Answer 23

Alachlor Acetochlor

Answer 24

Clomozone Balance

Answer 25

Glyphosate (ESPS) Immidiazilinone and Sulfonyl Ureas (ALS)

Answer 26

Aryloxy phenoxy (stops long chain fatty acid syn)

Answer 27

Herbicides not absorbed by foliage - only enters plants through roots May be too volatile May be photodecomposed and lost if not soil applied - Incorporation is needed May have low water solubility May only be root active and not translocated

Answer 28

Control weeds at very small growth stage Not as much herbicide needed to kill weeds Dont get much crop competition

Answer 29

Dont know which weeds will be the problem Dont know where problem areas are Some herbicides become environmental problems

Answer 30

Herbicides Applied to Soil (PRE Applications) - Meant to have residual effect (if not burndown) - Control germinating seedlings (if seedlings have emerged, some have no activity) - More environmental problems with soil applied herbicides - Some metabolites of the chemical remain toxic Atrazine to deethylatrazine Balance (isoxaflutole) (1/2 life 4 days) to DKN metabolite (highly active) (1/2 life 3 weeks plus) low sorption of each

Answer 31

Must come in **contact** with developing plant - Depth of application must be correct or need to leach to the zone needed - Dormant structures are not affected Herbicide must be there in high enough concentration - Reasons why the concentration may be low even if applied at the correct amount Degradation (microbial or chemical) Binding to soil (sorption decreases amount available to plant)

Answer 32

Soil Water Must be Present - Needed for seed germination, needed for herbicide uptake _Too Dry_ - Photodecomposition - Volatilization - No Seed Germination _Too Wet_ - Leach from Seed Zone - Runoff - Microbial Degradation

Answer 33

1-10% of Applied Herbicide Taken up either as Toxic chemical or Nontoxic metabolite

Answer 34

0 to 30% of Applied Sprayed On - no movement (ideal and usually not the case) Drift as spray droplets to nontarget areas (0 to 30% of applied) Volatilization (vapor drift) with movement in the air deposition with rain and snow Photodecomposition by UV light

Answer 35

50-100% of applied Sprayed On - lasts long enough to kill the target pest - no movement (ideal) Remains where it's at is nontoxic due to rapid breakdown (e.g. 2,4-D) or very high sorption (e.g. Roundup) Remains where it's at and continues to be toxic Remains where it's at degrades to another toxic product Movement to offsite areas as parent or metabolite (can be toxic or nontoxic) Mechanisms for movement (\< 1% of applied but still detectable) - Runoff - Leaching - Erosion

Answer 36

Herbicide moves in soil to the point of contact - with water (mass flow) - as a gas (diffusion) Herbicide **DOES NOT** move - Roots or shoots grow into and through the treated area (interception) Note: Some herbicides cannot be taken by roots, some cannot be taken up by shoots - Can use these properties to design where the chemical is placed to control the weeds of interest and not injure the crop

Answer 37

All Passive (through nonliving tissue) All Active (through cells and plasmodesmata) Mixture of Passive and Active

Answer 38

(Through nonliving tissue) (e.g. cell walls) Entry with water and movement in nonliving tissue (cell walls) and xylem

Answer 39

Through Cells and Plasmodesmata - Requires energy, moves in cell and symplast - If **phloem** only - the herbicide moves to the root actively growing cells, usually the root tip

Answer 40

Major barrier to herbicide movement - reason for why some herbicides are not taken up

Answer 41

Underground Shoot Adsorption (Thiocarbamates) - Coleoptile node of grass seedlings is the entry point - This is part of the leaf so there is no Casparian Strip - Hypocotyl and shoot of broadleaves are other entry points for herbicide

Answer 42

Group 8 - Thiocarbamates - Lipid Synthesis, not ACCase Gropu 15 - Acid Amides also called acetamides - Inhibits very long fatty acid synthesis

Answer 43

Group 3 - Dinitroanilines

Answer 44

Group 27 - HPPD Herbicides - 3 Families - Inhibits plastiquinone biosynthesis Group 13 - DOXP Herbicides - Inhibits isoprenoid synthesis

Answer 45

EPTC (Eptam) & butylate - Does not rely on post-application rainfall (but have to be incorporated due to high volatility) - Less loss from dry soil than from moist soil - Underground shoot absorption - Entry Point - coleoptile node of grass seedlings and hypocotyl hook of broadleaf - No problems with crop rotation restrictions - Only translocated in the **xylem**

Answer 46

Grasses may not emerge Reduces cuticular wax formation Leaves tightly rolled and do not unroll properly Broadleaf plants may have small leaves or 'bud seal' Roots may be brittle, short and thick

Answer 47

Shoot Inhibitors - Stop very long chain fatty acid formation (VLCFA herbicides) Drawstring (heart shaped) leaves Acid amide injury to soybean

Answer 48

_Injury_ Improper leaf unfurling Twisted whorls Buggy whipping _Conditions_ Misapplication Heavy rains soon after herbicide application that may leach away the herbicide safener Stressed conditions (cool, wet soils) Certain hybrids may be sensitive

Answer 49

_Site of Action_: Unknown _Mode of Action_: Inhibits synthesis of **very-long-chain fatty acids** in the **growing shoots** - membrane disruption - Stops growth - Elongase inhibition and inhibition of geranylgeranyl pyrophosphate cyclisation enzymes, part of the gibberellin pathway

Answer 50

No emergence of susceptible weeds (mostly grasses) Crops may be injured (cold, wet conditions; high application rate; improper placement) Sorghum is sensitive to injury _Symptoms Include_ Drawstring effect on broadleaf crop leaves - Also known as heart-shaped leaves May have buggy whipping on corn

Answer 51

Applied Preplant, PPI, Pre Used in corn, soybean, wheat, sunflower In corn and soybean mixed with metribuzin anad sold as AXIOM Maybe applied up to 14 days before planting, 10 gpa carrier minimum Used for grass and small seeded broadleaf control _Mode of Action_ is similar to acetochlor and metolachlor - Stops very long chain fatty acid synthesis, so membranes are disrupted

Answer 52

Used as preemergence or early postemergence (to the **crop**) but preemergences to **weeds** Can be impregnated on dry fertilizer Grass control and also some broadleaf control - amaranth - purslane - ragweed

Answer 53

Used in corn and soybean - 1-3.5 oz /ac depending on soil type - Needs 1/2 inch of rain to active herbicide - Minimum carrier volume is 5 gpa Can be fall applied, early preplant, ppi, pre or early post Grasses and Sedges

Answer 54

Trifluralin Pendimethalin

Answer 55

Root Inhibitors Used a dye intermediates All highly colored (orange, yellow) Some have fungicidal activity Taken up by germinating seedlings

Answer 56

Soil Applied Herbicide Pendimethalin - Applied pre to corn → **DO NOT** incorporate Treflan - If applied to corn, apply after corn is 8" tall and **incorporate** - **DO NOT** apply preplant or preemergence as injury can be severe

Answer 57

binds to a-tubulin - Mutations at certain points in this protein do not allow for binding and result in a resistant plant

Answer 58

Stops microtubules from assembling

Answer 59

Stunted Plants Roots Short and Thick

Answer 60

Adsorbed by roots and shoots Vapors can be adsorbed and kill plant Concentrates in - Areas high in lipid and proteins - If very hihg lipid content, binds herbicde and no injury

Answer 61

Roots - Inhibits lateral and secondary roots - Swelling of root tips and cell enlarge Shoots → Dicots - Decreased elongation, stunting - Leathery appearance of cotyledons - May be very dark green due to increasd chlorophyll

Answer 62

Inhibit 4 HPPD (3 Families) (WSSA Group 27) Isoxazole → isoxaflutole (Balance); pyrasulfotole (Huskie) Triketone → mesotrione (Callisto) Pyrazolone → topramezone (Impact) Inhibit DOXP Synthase (WSSA Group 13) Isoxazolidinone Family → Clomazone (Command)

Answer 63

Used pre or early preplant Corn, Sugar Cane Use for broadleaf weeds - excellent control of velvetleaf, control of ragweed, pigweed and some grasses (foxtails, barnyard grass)

Answer 64

Inhibits p-hydroxyphenyl pryuvate dioxygenase (HPPD)

Answer 65

Stops plastoquinone biosynthesis which leads to inhibition of cartenoid synthesis

Answer 66

Constituents (tetraterpenoid orangic molecules) of the plants that add **pigment** (color) to the leaf

Answer 67

Harvest Energy (i.e. Chlorophyll-photosynthesis) - Taking in the light energy & splitting water (ATP) Protect the leaf from free radicles and oxidative stress (xanthophylls and carotenes)

Answer 68

Plants are **bleached white** Tolerance of plants is due to rapid metabolism of the herbicide (herbicide is broken into smaller molecules) Degraded in soil by chemical and microbial means Some problems with carryover seen in the cool Midwestern soils and leaching

Answer 69

White Tissue (happens first) Poor Emergence Stunted Plants Growing point dies

Answer 70

Used pre or post in corn Used for control of Broadleaf weeds, cocklebur, velvetleaf, lambsquarters and some grasses ½ Life in Soil → 5 to 15 days Same site and mode of action as Balance Flexx - Inhibits HPPD, carotenoid biosynthesis, plants are bleached

Answer 71

DOXP Synthase (1-deoxy-D-xylulose-5-phosphate synthatase) that is a key component of isoprenoid synthesis - Different site of action than Balance Flexx adn Callisto

Answer 72

Similar to HPPD herbicides; stops carotenoid synthesis (pigment inhibitor) - Same symptoms as HPPD herbicides - Decreased carotenoid synthesis and **bleached** plants

Answer 73

Used in soybean and processing pumpkings (ornamental pumpkings are sensitive) Soybean not injured the plant **metabolizes** the herbicide Controls annual grasses and some broadleaf weeds such as velvetleaf Problems with **drift** due to **volatization** problems from wet or moist soils

Answer 74

Wind Speed - Higher speed, more drift Inversion Conditions - Inversion more movement close to ground Distance to the nontarget area - Further the distance to offset areas (large buffer zone) less risk of contamination Droplet size Smaller droplets - further drift

Answer 75

Spray Timing (plant size/cover) Formulation and Additives Application Equipment (droplet size) Plant properties (hairs, smooth, waxy) Time to rain (rainfastness)

Answer 76

Uptake more difficult than through root Factors affection foliar sorption Retention - Dependent on carrier Water "falls" off leaf - lack of wetting and spreading Granules - Bounce off

Answer 77

Help water spread and adhere to leaf Reduce surface water tension Allow closer contact of the herbicide with the leaf surface Help minimize runoff (help water stick to the leaf)

Answer 78

Dependent on Drying Time - If dries too quickly get residues than will not enter plant - If the herbicide does not dry quickly enough may get washed of by rainfall

Answer 79

Cuticle Cell Wall Plasmalemma

Answer 80

By diffusion (passive process from high to low concentration) Moves through - Intermolecular Spaces - Pectin Spaces (if water soluble) - Embedded Waxes (if nonpolar) Depends on the Chemistry of the Herbicide Nonpolar Molecules (like EC formulations) Can **easily** move through **wax** but dont move through water well Polar Molecules (like amine formulations) **Cannot move** through wax but once in the leaf can **move** in polar (pectin or water filled spaces

Answer 81

Made up of Cellulose Strands Interspaces fill with water Water soluble herbicides penetrate the cell water easier than EC type herbicides Movement in the cell wall is by **diffusion**

Answer 82

Outer membrane of the living cell that encloses cytoplasm For most herbicides penetration into the cell is by **active transport** cell has to expend energy If the herbicide does not get through the plasmalemma and into the cell - usually is ineffective

Answer 83

PPO Inhibitors (Group 14) Photosynthetic Inhibitors → Triazines (Group 5) Meristem Inhibitors (ALS Enzyme Inhibitors) → IMI and SU (Group 2)

Answer 84

Cell Membrane Disruption

Answer 85

Inhibiton of protoporphyrinogen oxidase (Protox or PPO Inhibitors)

Answer 86

Sharpen (other applied post) PPO is an enzyme of chlorophyll and heme biosynthesis Inhibition of PPO leads to accumulation of a chlorophyll precursor (PPIX) PPIX then absorbs light and causes single oxgen to form Leads to membrane breakdown via lipid peroxidation

Answer 87

Used for broadleaf weeds (pigweed, waterhemp, wild buckwheat) Applied at 2 oz/ac in coarse (sandy) soils up to 3 oz/ac in fine (clay) soils Tank-mixed with many herbicides

Answer 88

Active at low rates - 1/3 to ½ oz per acre (**do not** overapply) Specific Herbicide Dictates - Crop (corn, soybean, wheat, sugarbeet) - Weed Spectrum (some best on broadleaves, some control grasses and broadleaf weeds)

Answer 89

Resistant weed populations built up in as little as **2 cycles** of use Some weeds including kochia and prickly lettuce which were very well controlled after one application showed resistance after **2 or 3** applications Use some of ALS type herbicide once every **48 months**

Answer 90

Carryover (even if applied at ½ oz rate) to sensitive crops several years after application Longer carryover if soil pH is 8 or greater Example Red River Valley North Dakota

Answer 91

Used for broadleaf weed control in wheat, barlet Applied pre or post up to 2" Problems with carryover, resistant weeds Active at low rates

Answer 92

½ life 4 to 6 weed if pH \< 7 ½ life up to 3 years \> 7 - In high pH soils, problems with rotational crops such as sugar beets, sunflowers, lentils, chlorsulfuron at \<1 ppb can cause problems Breakdown is through hydrolysis at urea group and occurs much faster in low pH (7 or lower) soils Not bound to soil - leaching and carryover problems

Answer 93

Annual broadleaf control in soybean Used pre or pst Used at higher rate than Glean (.5 to .75 oz/ac) Antagonism if applied with post grass herbicide

Answer 94

Used pre and post for broadleaf control in soybean Use rate about 2 oz a.e./ac ½ Life - Long persistence in some environments - 1 year restriction on corn following application

Answer 95

Used in legume crops for broadleaf and grass control at 4 to 6 oz rate - PPI - Pre - Post Clearfield corn Selected for resistance (nonGMO) and allows for Pursuit/Lightning to be used for control Clearfield Rice/Canola/Sunflowers

Answer 96

Used for common cocklebur, wild buckwheat, NonALS kochia, Lambsquarters, barnyardgrass, foxtails ½ life 4 months but can be longer IMI resistant corn (Clearfield or Lightning) developed for that reason Problems with resistant weeds and cross resistnace to SU herbicides

Answer 97

Used in soybean Pre or Early Post Used for broadleaf weed control - ragweed (common and giant), marestail, velvetleaf Can be mixed with Roundup in RR soybean and other broadleaf and grass herbicides Use rates .3 oz product/ac - post and .6-.75 oz product/ac pre

Answer 98

Broadleaf control in corn and soybean Only applied preemergence (preplant, ppi or pre) Restrictions on some rotational crops - Sweet corn and sunflower - 18 months - 26 months cannola, sugar beets

Answer 99

Phenoxy (Aromatic carboxylic) acids (2,4-D; MCPA; 2,4-DB) Benzoic Acids (Banvel, Clarity) Picolinic Acids or Pyidines (Tordon, Milestone, Quelex halauxifen for wheat)

Answer 100

Naturally occuring plant growth hormone (in form of IAA) - Move from site of production to site of aciton

Answer 101

Increased respiration due to uncoupling of oxidative phosphorylation (ATP is no longer produced from ADP in the mitochondria) Decreased photosynthesis In plant roots **inhibits** - Elongation of cells (plants have short stubby roots) - Decreased water uptake by roots - Leads to decreased transpiration (leaves get hot) - Stomatal closure (no carbon dioxide enters) - Even lower photosynthesis

Answer 102

Translocated (moved in the plant) in the **symplast** (living tissue of the plant; moved in the phloem) Moves to **actively growing** shoot and root tips - Shoots elongate, get epinasty (twisting and bending of stems due to ethylene production) - Vascular tissue destroyed due to unchecked cell division - Roots stop growing, get stubby roots - If applied when flower initials are forming will cause infertility problems or malformed flowers

Answer 103

Selective Herbicides (does not control all weed types) Control **broadleaves** weeds the best - Although poor control of weeds in Polygonum (smartweed) family Grasses - May be killed if applied at seedling stage - Injury occurs if applied at a susceptible stage (tillering and boot of cereals) 2,4-D was the first high potency herbicide (use rate 1 to 4 lb/ac)

Answer 104

Used to control **Broadleaf Weeds** in - Corn - Wheat - Pastures - Noncropland Will kill or injure grasses if appliked at critical times Tank-mix partner with many herbicides

Answer 105

Epinasty - Bending of stems due to differentinal growth rates of elongating regions Thickening of stems and leaves Cupping and Twisting of stem Brace root proliferation (corn plants) **Timing is key** on grass plants to avoid injury (malformed roots, sterile flowers)

Answer 106

Broadleaf control in grass (grain, corn) - does not control mustard Pre emergence applications can control some grasses Drift and Volatility Problems - Soybean very sensitive to dicamba - Injury can occur at rates 50 x lower than 2,4-D If applied too late to corn, cracking and brittle stems

Answer 107

Absorbed by Foliage (some root uptake) Translocated in phloems (some in xylem) Accumulates in meristems Can be exuded into soil and taken up by other plants Acts like 2,4-D (alters nucleic acid synthesis, etc.) Tolerant plants metabolize dicamba rapidly

Answer 108

Not adsorbed by soil Can leach readily into and through root zone Can be a problem if need to replant less tolerant crop

Answer 109

Act like Auxin Highly toxic - 100 times more active than 2,4-D Used for broadleaf weeds in grass, pasture, range, forest Adsorbed through roots and foliage Damage looks like 2,4-D

Answer 110

Acid not water soluble so derivatized to: - Na Salt - Isopropyl amine salt Premixed only with - 2,4-D

Answer 111

Broadleaf weed control in grainland, fallow, noncrop, forest, range, pasture - Does not control mustards - Do not rotate to broadleaf crops Translocated mostly symplastically Plant growth reponse similar to 2,4-D Not metabolized in plants

Answer 112

Known for **Canada thistle** control Also used for other broadleaf weed control in - Sugar beets - Corn - Wheat, Barley, Oats - Rangeland, Pasture, Noncropland, CRP Readily translocated in the phloem

Answer 113

Inhibits polar transport of IAA

Answer 114

Abnormal accumulation of IAA which causes imbalances in shoots and roots and inhibits growth

Answer 115

Sensitive broadleaf weeds exhibit rapid and severe plant hormonal effects (e.g. epinasty) after application of Distinct Symptoms are visible within hours Plant death usually occurs within a few days Corn tolerant becasue of rapid metabolism

Answer 116

Glyphosate (Roundup) Glufosinate (Liberty)

Answer 117

Enol pyruvyl shikimic acid phosphatase (EPSP) enzyme

Answer 118

Inhibits aromatic amino acid synthesis Amino acids not formed - tyrosine - phenylalnine - tryptophane This leads to problems with protein synthesis

Answer 119

Very strong adsorptoin to soil - Binds with Fe, Ca, Al - Compounds not taken up unless in solution Very little leaching No carryover Microbial degradation is major means of degradation in soil

Answer 120

Absorbed by foliage Translocated to meristems and root buds in the phloem Visual Effects - Sometimes deep purpling (wild buckwheat, corn) ~ Stunting ~ Chlorosis (yellowing of tissue) ~ Wilting ~ Tissue Necrosis (dead tissue) - Seen after ~ 5 to 15 days depending on annual/perennial

Answer 121

Do not combine with - Wettable powders or dry flowable (binds irreversibly to the clay particles) - Hard or dirty water (binds with iron, calcium and soil) Maybe washed off by rain and have no activity - Some formulations are better sorbed and have more rainfastness than others - Use with surfactants and at times fertilizers to increase uptake (Use AMS not UAN)

Answer 122

Amino acid Herbicide Not water soluble - formulated as an ammonium salt (described as a.e.) Nonselective Herbicide - Kills grasses and broadleaf weeds - Used **post** emergence only - **No soil activity** - Works best when the growing point of corn is emerged from soil (30" corn) Liberty and Ignite are not easily taken up

Answer 123

*Glutamine synthase* an enzyme that converts glutamate + ammonia to glutamine

Answer 124

When glutamine synthase is stopped toxic accumulations of ammonia are found in plant tissue

Answer 125

Chlorsis (yellowing of tissue) and Wilting 3 to 5 days after application Necrosis (dead tissue) 1 to 2 weeks

Answer 126

Aryloxyphenoxies ('fops', 'props' and 'dops') Cyclohexanediones ('dims') Pinoxaden ('dens')

Answer 127

Blocks the **ACCase** (acetyl CoA carboxylase) enzyme

Answer 128

Stops acetyle CoA from going to malonyl CoA, the first step of fatty acid synthesis; inhibition of long chain fatty acid synthesis Long Chain Fatty Acids needed for cell membranes - No membranes, no cell integrity - No new growth - Plant death

Answer 129

Grass Herbicides Symptoms - Root and shoot growth slow soon after application (seen as stunting) - Purpling of Steam - 'Mushy' growing point

Answer 130

Used for post-emergence grass control (wild oat, foxtail, crabgrass) in barley and wheat Applied when susceptible grass is in the 1 to 4 leaf stage Controls downy brome if applied ppi Need Good Coverage Inhibits Shoot Growth

Answer 131

Slow to Develop Chlorosis and Stunting of Plant Degrades quickly ½ life → 10 to 30 days

Answer 132

Post Emergence Grass Control - Volunteer Corn - Quackgrass Absorbed by foliage and translocated Inhibits ACCase activity

Answer 133

Symptoms - Stunting - Chlorosis - Necrosis - Decayed growing point Symptoms slow to develop Low soil mobility ½ Life → less than 1 week

Answer 134

Used for post emergence annual grass control in alfalfa, soybean and sunflower Increased uptake when mixed with crop oil ACCase Inhibitor ½ Life → 2 to 13 days

Answer 135

Selective (only kill broadleaf) Photosynthetic Inhibitor - Bentazon (Basagran) → Broadleaf (Group 6) - Bromoxynil (Buctril) → Broafleaf (Group 5) Selective (kill grass only) Difenzoquat (Group 26, site unknown) Selective (kills broadleaf and grasses, not crops) PPO Inhibitors → Group 14 Nonselective (kills all plants) Paraquat → Group 22

Answer 136

Photosystem II in chlorophyll of plant - site B

Answer 137

Inhibits electron transport in Photosytem II - Binds to an amino acid in the protein bound plastiquinone enzyme and does not allow electron transport to continue (stopping photosynthesis)

Answer 138

Chlorosis - If not good coverage, yellow spotting Necrosis Wilting Stunting Tolerant crops may show these symptoms form slight to moderate (depending on variety)

Answer 139

Very water soluble but not leached due to binding with soil Soil persistence 3 to 5 months but not active cause - Tightly bound - Does not translocate well to the leaves of the plants (site of action)

Answer 140

Photosystem II (same as bentazon)

Answer 141

Appliked Post to: - Wheat - Barley - Oats For seedling broadleaf control Best when weeds are small, \< 4 leaf stage Controls - Wild buckwheat - Annual smartweed These are weeds that 2,4-D does not control well

Answer 142

Inhibits photosynthesis by stopping electron flow in PSII so no reducing power is generated in photosynthesis - Secondary effect is lipid peroxidation which causes holes in membranes, loss of cell integrity follwed by loss of cell function

Answer 143

Leaf Chlorosis (due to lipid peroxidation) Leaf spotting if poor coverage Necrosis

Answer 144

Inhibits carotene biosynthesis (protoporyhyringen) (Protox or PPO)

Answer 145

Oxidation of membranes and cell constituents (breaks down membranes) because singlet Oxygen builds up - carotene buffers against singlet O formation

Answer 146

Water Soaking Wilting Foliage burn

Answer 147

Early postemergence broadleaf and small control in soybean Excellent control of - Pigweed - Mustard - Black Nightshade Poor control of large seeded weeds (sunflower) Contact Herbicide - need excellent coverage

Answer 148

Nonselective Contact Herbicide Used in lots of crops to dry down (i.e potatoes) Used to dessicate weeds at the end of the season prior to harvest Used as burndown in spring Does not translocate - poor control of perennials

Answer 149

Plant dessication Rapid wilting due to disruption of membranes and water loss of cells Cocklebur (mature and drought stressed) are tolerant to paraquat

Answer 150

A free radical is formed using paraquat and keeps reoxidizing to paraquat - reoxidation results in Hydrogen peroxide (H₂O₂) production which destroys cell membrane

Answer 151

Photosystem I in chlorophyll the paraquat molecule acts as a free radical and scavenges electrons from photosynthesis and also respiration

Answer 152

The inherited ability of a plant to survive and reprouce following exposure to a dose of herbicide that is lethal to the wild plant type

Answer 153

Ability of a plant to survive and reproduce after herbicide treatment

Answer 154

Plants that are resistant to several herbicides in a similar chemical group with a similar mode of action

Answer 155

Plant is resistant to herbicides that are chemically unrelated and have different mode of actions

Answer 156

Over reliance/exclusive reliance on a single herbicide (or herbicide mode of action) for weed control - Single site of action increases problems (ALS, ACCase, glyphosate, PPO, PSII, all ahve single site of action) An increase in the application frequency of a particular herbicide

Answer 157

Use integrated weed managment techniques Prevention is the best method Diverse program is needed Tank mix at least 2 chemicals with different sites of action Then: - Rotate Culivation Techniques

Answer 158

Use herbicides with short-term soil activity Use optimum doses to prevent weed escape Use cultural managment to prevent weed seed spread Tank mix different sites of action It is recommended **not** to use herbicides with the same site of action more than **once** every 3 years

Answer 159

Which weeds What method of control - May not alwasy choose an herbicide Where present What mode of action or combination - Whats been used in the past What stage of plant growth (when to apply) - Choose the right timing What rate

Final Exam Flashcards

(187 cards)