weed science final

• • What is a herbicide? 
  • An organic chemical compound
  • Selective or non selective control
  • Classified as a pesticide
• • What federal agents govern herbicides? 
  • EPA
• • How long does it take to get a herbicide registered? 
  • 11 years
• • What laws and regulations govern herbicides? 
  • EPA, FDA, OSHA, USDA
• • What do the laws and regulations do? 
  • Safe drinking water, clean water, FIFRA, labeling, worker protection, training, food quality
• • How much does it cost? 
  • $280 million
• • How many regulations make it through? 
  • 1 out of 20,000
• • Is active ingredient or formulated used? 
  • Formulated
• • What is the colby equation used for? 
  • Herbicide synergism or antagonism
• • Can herbicides cause mutation in weeds? 
  • No
• • Glyphosate resistance? When and what species? 
  • 1997 - goosegrass - malaysia
• • Bacteria species: what do we get? Shoot into corn 
  • Particle gun technology
• Tomatoes can be transgenic? Yes
• • Herbicide resistance development
  • Naturally occurring mutations from small preexisting populations within a species
• • Mode of action: symptoms that occur after herbicide application leading to plant death 
  • Site of action: specific location at which herbicides exert their toxicity at the cellular level
• • Susceptibility vs tolerance vs resistance 
  • Susceptibility: plant will die from herbicide applied at normal use rate 
  • Tolerance: plant won’t be injured by a herbicide at rates normally used to control other species 
  • Resistance: was once susceptible to a herbicide but now isn’t
• • Why do producers like transgenic cropping systems? 
  • Plant breeding 
  • Genetic engineering 
  • Can increase yield, cheaper, and they are consistent
• • Herbicide interactions, what is most common, what are they?
  • Additive: total response = sum total of response 
  • Synergistic: total response is greater than sum total of response 
  • Antagonistic: total response is less than sum total of response 
  • Enhancement
  • Synergistic and antagonistic = most common
• • Barrier to entry of soil herbicide 
  • Casparain strip 
  • Plasmalemma of epidermal and corticular cells
• • Major plant processes - where herbicides can inhibit plant growth (7)
  • Mitosis
  • Cellulose
  • Shoot 
  • Chlorophyll 
  • Carotenoid 
  • PPOS (protox)
• • Factors that contribute to herbicide selectivity (4) and examples 
  • Physical: soil applied - herbicide rate and  foliar applied - herbicide placement 
  • Biological: physiological factors - leaves 
  • Chemical plant protectants: protect a crop from a toxic action of herbicide - safener
  • Chemical herbicide protectants: coating a seed coat with safener
• • How to manage a field to undo herbicide resistance? 
  • Use herbicides with differents mode of actions 
  • Crop rotation or tillage 
  • Reduce seed bank
  • IWM approach
• Types of translocation in plants

  • Short distance
  • Long distance
• Short distance translocation

  • Intracellular transport: movement of ions and molecules within an individual cell
  • Extracellular transport: movement of ion and molecules in the cuticle and the apoplast
  • Intercellular transport: movement of ions and molecules from cell to cell via symplast
• Long distance translocation

  • Xylem transport: ions and molecules that move to the xylem are transported upward in the plant via transpiration stream from the roots and other underground parts
  • Phloem transport: herbicides that move to the phloem are transported downward in the plants via photosynthate stream from the leaves and other underground parts