Herbicides

• better understanding of how herbicides perform
• improve herbicide performance
• Diagnose herbicide injury

• photosynthesis (food)
• pigments (energy/light capture)
• respiration (energy)
• amino acids (protein/growth)
• lipids (cell membranes)
• mitosis (cell division)

• Reduce impact of invasive species
• secure the presence of targeted species

• Selective-controls one species of plant without affecting the growth of another species (2 4-D)
• Nonselective- controls plants regardless of species (Roundup)

• foliar contact
• root contact
• xylem
• xylem & phloem
• phloem

sequence of events from absorption of the herbicide into the plant until the plant dies

• plant growth regulators
• amino acid biosynthesis inhibitors

• photosynthesis inhibitors
• cell membrane disrupters

• synthetic auxins (regulate plant growth)
• affect several plant processes like cell division, cell enlargement, protein synthesis and respiration
• act by upsetting the normal hormonal blance in plants

• foliar contact
• root contact
• translocated in both xylem & phloem

• broadleaf plants
• injury may occur in grasses
• (2 4-D)

• on newly developed leaves
• abnormal growth causing twisting stems
• stems swell cuz of rapid cell division
• leaves exhibit cupping, crinkling, strapping or drawstring affect
• symptoms on grasses include leaf rolling, crinkling, brace root fusion and malformation
• flower sterillity and missing grain in crops

• herbicide resistance
• drift and injury to nontarget plants
• groundwater contamination

• prevent synthesis of certain amino acids produced by plants
• excellent foliar and root absorption
• broad weed spectrum
• translocates to shoot and root new growth in both xylem and phloem
• (Roundup)
• plants stop growing shortly after application
• plant death may be slow (10+ days)

• chlorosis of leaves (turn yellow)
• stunted growth

EPSP inhibitors

• tightly absorbed and inactive in soil
• phloem translocated
• inhibits EPSP enzyme responsible for production of aromatic amino acids
• very nontoxic

• control annual or perennial grasses or broadleaves
• shut down the photosynthesis process
• slow starvation of the plant
• plant experiences more rapid death due to production of secondary toxic substances
• injury symptoms: yellowing of leaf tissue followed by death of the tissue
• (Spike 20P)

• occur after coteyledons and first leaves emerge (Dont prevent seedlings from germinating or emerging)
• yellowing (chlorosis) of leaf tissue followed by death (necrosis) of tissue
• older and larger leaves affected first

• postemergence contact herbicides
• little soil activity
• activated by exposure to sunlight to form oxygen compounds such as hydrogen peroxide
• oxygen compounds destroy plant tissue by rupturing plant cell membranes
• perennial weeds usually regrow cuz there is no herbicide movement to underground root or shoot systems
• controls weeds in 24-48 hours
• broad-spectrum and non-selective control of grasses, broadleaf weeds and sedges
• no residual effect
• gramoxone max

rapid necrosis (cell death)

• sprayer skips or plugged nozzles
• weather problems that cause poor control
• plants that are naturally tolerant to herbicide
• genetic changes caused by herbicide

the ability of a plant to survive and reproduce after treatment with a dose of herbicide that would normally kill a plant