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68 Cards in this Set

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What is the goal of formulations?
storage, mix/spray in water, get it in the plant, and minimize off-target damage
What chemical processes affect persistence?
adsorption, photodecomposition, hydrolysis
What biological processes affect persistence?
microbial, detoxification
What is mode-of-action?
symptoms that occur after herbicide application leading to plant death
What is mechanism-of-action?
actual biochemical site of herbicide activity
What is the difference between contact and systemic herbicides?
- contact herbicides only affect what they hit
- systemic herbicides move throughout the plant
What are the 4 mechanisms of herbicide selectivity in plants?
- placement
- differential uptake
- metabolism
- differential binding at the enzyme level
What are some mechanisms of tolerance?
- herbicide X not absorbed
- X does not bind to enzyme Y
- X metabolized to Z
- Sequestered in vacuole
What are the 7 mechanisms of action?
1. photosynthesis
2. amino acids and proteins
3. fatty acid synthesis
4. growth inhibition
5. cell membranes
6. pigment synthesis
7. growth regulation
What do photosynthetic inhibitors do?
- inhibit photosystem II
- blocks the flow of energy from chlorophyll to the intermediates
- forms oxygen radicals which are toxic
What group are Substituted Ureas in, what is a compound, and how does it move in the plant?
- Photosynthetic Inhibitor
- Diuron (Karmex)
- root uptake, translocated via water stream
What group are Triazines in, what is a compound, and how does it move in the plant?
- Photosynthetic Inhibitor
- Atrazine
- root uptake, translocated via water stream
What group are Uracils in, what is a compound, and how does it move in the plant?
- Photosynthetic Inhibitor
- Bromacil
- root uptake, translocated via water stream
What group are Benzonitriles in?
- Photosynthetic Inhibitor
What group are Carbamates in and how does it move in the plant?
- Photosynthetic Inhibitor
- contact
What group is Bentazon in?
- Photosynthetic Inhibitors
What are the symptoms of photosynthetic inhibitors?
interveinal or veinal chlorosis
What do amino acid synthesis inhibitors do?
target a specific enzyme
Which mechanims has better control with more growth?
amino acid inhibitors
Provide the following info for Imidazolinones:
group
Amino acids inhibited
application
selectivity
- Amino Acid Inhibitor
- Valine, leucine, isoleucine
- PPI, PRE or POST
- Metabolism or differential enzyme selectivity
What symptoms do Imis cause?
new leaves stunted, purple streaks
What group are Sulfonylureas in?
Amino Acid inhibitors
What group are Sulfonanilides and Pyrithiobac in?
AA inhibitors
Which AA inhibitor has no soil activity?
Glyphosate
What does Glyphosate block?
aromatic amino acids
What does Glufosinate block?
incorporation of nitrogen in amino acids causing the buildup of toxic levels of ammonium
What are symptoms of glyphosate?
- multiple shoots as regrowth
- initial chlorosis followed by necrosis
- slow death
What is the effect of fatty acid synthesis inhibitors?
stunted growth and eventually death due to lack of membranes for cellular integrity
Where are fatty acids?
primary building components of cell membranes and many intercellular membranes
What group is Aryl-oxy-Phenoxys and cyclohexadiones in, what is the name of a compound in it and what types of plant do they affect?
- Fatty acid synthesis inhibitor
- Select
- grasses
What group are Amides/Chloroacetamides?
fatty acid synthesis inhibitors
What group is Thiocarbamates in and name a compound belonging to the group?
fatty acid synth inhibitors
Metam
What is the primary pesticide law?
Federal Insecticide, Fungicide and Rodenticide Act
Define LD50 and LC50.
LD50 is the lethal dose that causes death in 50% of the test population.
LC50 is the concentration that causes death in 50% of the test population
Name 4 ways in which a herbicide may be broken down (dissipated) in the natural environment.
volatilization, adsorption, leaching, wind or water erosion
What is the difference between trade, common and chemical name?
trade name is from marketing and lives with the life of the product, common name is the active ingredients, chemical name is the IUPAC approved name, internationally recognized
How does capillary flow affect the fate of herbicides in the environment?
it increase the flow of herbicides and salts upward in soil/water fraction; associated with leaching
What are the 3 physical processes that affect environmental fate of herbicides and what increases them?
volatility- hot and windy
leaching- sandy soils, high rain
erosion- high rain in short time
What are the 3 chemical processes that affect environmental fate of herbicides and what factor affect them?
adsorption- sandy soils, variable pH decreases it
photodecompostion- high light increases it
hydrolysis
Explain the 4 mechanisms of herbicide selectivity in plants?
1) Placement- crop does not take up the herbicide while the weeds do
2) Differential uptake- crop takes up less herbicide
3) Metabolism- breaks down herbicide via oxidation, dehydroxylation, reduction (glutathione or AA conjugation, or sequestration in vacuole)
4) Differential binding at enzyme level- the herbicide binds to the weed enzyme but not the crop enzyme
Explain how growth inhibitors work and the mode of action.
Most are soil applied affecting seedling weeds. Most interfere with mitosis while other appear to prevent lipid (cell membrane) production. Some prevent cell wall formation. Little movement once absorbed.
MOA- prevent root and shoot growth
What group is Dinitroanalines in, what is a herbicide in that group, and what is the mechanism?
Growth Inhibitors
Prowl
inhibit cell division
What group is Dichlobenil in and what is the mechanism?
Growth Inhibitors
Inhibit cell wall formation
What group is Isoxaben in and what is the mechanism?
Growth Inhibitors
Inhibit cell wall formation
What factors influence herbicide movement into plant tissue?
polarity
formulation
molecular size and weight
adjuvant and carriers
What is the difference between apoplastic and symplastic movement?
Apoplastic movemt go thru non-living tissues (xylem) with water flow diffusion and mass flow (passive process); goes only up.
symplastic movemt goes thru living tissues which are bound by plasmalemma and vacuole membrane through phloem and accumulate in growing regions
How are herbicides taken through the roots?
- primarily apoplastic movement, xylem flow as water, ions aremoved up in the plant
- herbicide must have the ability to cross the endodermis (Casperian strip)
- passive but can still move symplastically but goes through apoplastic first
How are herbicides moved through foliar uptake?
- primarily diffusion into plant cells then symplastic movemt if not a contact herbicide
- barriers include plasmalemma and cuticle
What conditions are needed on the pesticide label as required by EPA?
Applied, Mixed, Stored, Loaded or used, Reentry time, Crop harvest interval, Disposed of properly
What does the FDA do?
share food safety responsibilities with EPA, set food tolerances
What does OSHA do?
Worker Protection Standard- protects ag workers and pesticide handlers
- establishes REI
- Defines Ag Use Reqmts
What does cell membrane disruptors do?
divert normal energy flow to form toxic intermediates
- interact with membrane and cause disruption
- cause the membrane to become "leaky"
- contact herbicide
What group is Bipyridylliums in, what is a herbicide, and what is its mechanism?
- Cell Membrane Disruptors
- paraquat
- diverts normal electron flow from PSI causing formation of radical oxygen and cell membrane disruption
What do you need to do on the farm to have cell membrane inhibitors to be effective?
good coverage
What group is Organic Arsenicals in, what is a herbicide, and what is its mechanism?
- Cell Membrane Disruptors
- MSMA
- interferes with energy transfer, enzymes
- causes chlorosis, stunting, dessication
What group is PPO Inhibitors in, what is a herbicide, and what is its mechanism?
- Cell Membrane Inhibitors
- Valor
- increase pre-chlorophylls from forming free radicals
- move apoplasticly when applied to soil
- contact when applied foliar
What group is Copper in?
- Cell Membrane Disruptors
- Disrupt cell membranes
What group is Diphenylether in, what is a herbicide, and what is its mechanism?
- Cell membrane disruptors
- fomesafen
- PPO inhibitor
What do Pigment Synthesis Inhibitors do?
- block the formation of chlorophyll and carotenoids
- move through apoplasm
What group is Clomazone in and what is its mechanism?
- Pigment Synthesis Inhibitors
- inhibits chlorophyll synthesis
What group is Pyridazinones in, what is a herbicide, and what is its mechanism?
- pigment synthesis inhibitors
- Sonar
- apoplastic then symplastic
- inhibit synthesis of carotenoids
What group is Mesotrione and isoxaflutole in and what is its mechanism?
- pigment synthesis inhibitors
- blocks the fromation fo a precursor needed for carotenoid synthesis
- turns plants white
What do growth regulators do?
- auxin mimics
- auxin transport inhibitors
- soil and foliar applied, systemic
What group is Benzoic Acids in, what is a herbicide, and what is its mechanism?
- growth regulators
- dicamba
- symplastic
- interferes with RNA, DNA and protien synthesis
- causes rapid, uncontrolled growth
What group is Phenoxys in, what is a herbicide, and what is its mechanism?
- growth regulators
- 2,4-D
- salt, ester and oil formulations
- foliar and root uptake
- cells undergo rapid uncontrolled division and elongation
What group is Picolinic acids in, what is a herbicide, and what is its mechanism?
- growth regulators
- Triclopyr
- foliar and root uptake
- cells undergo rapid uncontrolled division and elongation
What group is Diflufenzopyr in and what is its mechanism?
- growth regulators
- foliar and root adsorbed
- interferes with auxin movement and translocation
What group is Quinclorac and what is its mechanism?
- growth regulators
- blocks auxin transport