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