Agenda
•
•
•
•

PRE MOA presentation
Assign topics for future practices
Make wish list for Vince
Seminar Blair Miller: Why...
Herbicide MOA
(Preemergence)

University of Wisconsin-Madison
Weeds Team 2013
According to Facebook
According to Bill Nye the
Science Guy
Herbicide MOA
(Preemergence)

University of Wisconsin-Madison
Weeds Team 2013
Disclaimer
• Wide range of background in this room, stop
me with questions anytime
– We will talk about Mode of Action (in...
Herbicide Mode and Site of Action
• Mode of Action
– the metabolic or physiological process impaired or
inhibited by the h...
Herbicide List (PRE) by SoA
• PSII, D1protein (Photosystem 2 Inhibitors)
– atrazine, metribuzin

• PPO (protoporphyrinogen...
Other ways to categorize herbicides
• MOA
–
–
–
–
–

PSII = photosynthesis inhibitors
HPPD =pigment inhibitors
MI =seedlin...
Herbicide List
• list
Photosynthetic Inhibitors (primarily soil-applied)
Triazines
atrazine (AAtrex)

metribuzin (Sencor)
Injury Symptoms of Soil-Applied PSI
• Injury symptoms appear after the food reserves in
the cotyledons have been exhausted...
Injury Symptoms of Soil-Applied PSI
• Injury symptoms appear as a yellowing (chlorosis) of
the leaf tissue which, if sever...
Interveinal Chlorosis in cotton
Chlorophyll
• Pigments are molecules that absorb light
– Sunlight

Pigments

PS

Food

• Chlorophyll is the plant pigment ...
Protoporphyrinogen Oxidase Inhibitors
• These herbicides inhibit a step in the chlorophyll
biosynthesis pathway
– protopor...
Protoporphyrinogen Oxidase Inhibitors
N-Phenylphthalimides
flumioxazin (Valor)

Aryl Triazolinone
sulfentrazone (Authority...
Injury Symptoms of PPO Inhibitors
• Soil-applied PPO inhibitors are mobile within
the plant
• Injury often related to mult...
Tim says: chlorotic veins in soybeans
and corn for soil applied PPO injury
Carotenoid Synthesis Inhibitors (Bleachers)
• Carotenoids are “accessory” plant pigments that
protect chlorophyll during p...
Bleachers
• Absorbed through roots and shoots, but
translocated only in the xylem
• Prevents synthesis of pigments that pr...
Ross is not funny
Carotenoid Synthesis Inhibitors
Isoxazalidinones
clomazone (Command)

Isoxazoles
isoxaflutole (Balance)
Injury Symptoms of Carotenoid Synthesis
Inhibitors
• Corn foliage is white
– lack of carotenoids leads to destruction of c...
Command Carryover in Oats
Balance Injury, cold wet conditions
Light-activated Herbicides
• How bored is everyone/how am I doing on
time
• Reichers explains as multiple SOAs, but kind o...
Seedling Growth Inhibitors
• These herbicides inhibit the growth and
development of weed seedlings, usually before
the wee...
Cell Reproduction
• Cell division (mitosis) is the process by which cells
reproduce
• During cell division the genetic mat...
Dinitroaniline Herbicides
SoA: Microtubule Inhibition

trifluralin (Treflan, others)
pendimethalin (Prowl)
Injury Symptoms of DNA Herbicides
• Corn seedlings are usually stunted with club-shaped
roots and limited secondary root d...
Chloroacetamide Herbicides
• These herbicides inhibit primarily shoot
development in susceptible species
– root symptoms n...
Chloroacetamides and Thiocarbamates
Chloroacetamides
S-metolachlor (Dual II Magnum)
acetochlor (Harness,TopNotch, etc)
Injury Symptoms of Chloroacetamides
• Injury symptoms are most frequent under cool, wet
conditions
– those conditions that...
Injury Symptoms of Chloroacetamides
• Soybean leaves may also appear crinkled or puckered.
A shortened leaf mid-vein gives...
Buggy
Whipping
“Stumble up to a plot”
• We talked a lot about how herbicides work
and their symptomology
• Next step is to put together k...
Quiz next week!!!
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Moa pre final

  1. 1. Agenda • • • • PRE MOA presentation Assign topics for future practices Make wish list for Vince Seminar Blair Miller: Why not ‘Nature Mark’ potato?
  2. 2. Herbicide MOA (Preemergence) University of Wisconsin-Madison Weeds Team 2013
  3. 3. According to Facebook
  4. 4. According to Bill Nye the Science Guy
  5. 5. Herbicide MOA (Preemergence) University of Wisconsin-Madison Weeds Team 2013
  6. 6. Disclaimer • Wide range of background in this room, stop me with questions anytime – We will talk about Mode of Action (includes some herbicide physiology) – Then get into symptomology and selectivity • ok presentation for teaching MOA(not great), since it is geared for contest – Leaving out elements not important for contest • Very reduced amount of herbicides discussed
  7. 7. Herbicide Mode and Site of Action • Mode of Action – the metabolic or physiological process impaired or inhibited by the herbicide • HOW the herbicide controls the plant • Site of Action – the physical location within the plant where the herbicide must bind to exert its MOA • WHERE the herbicide acts within the plant
  8. 8. Herbicide List (PRE) by SoA • PSII, D1protein (Photosystem 2 Inhibitors) – atrazine, metribuzin • PPO (protoporphyrinogen oxidase inhibitors) – flumioxazin, saflufenacil, sulfentrazone • HPPD & Diterpene (P-hydroxyphenylpyruvate dioxygenase inhibitor) – isoxaflutole, clomazone • Microtubule Inhibitors – pendimethalin, trifluralin • VLCFA (Very long chain fatty acid inhibitors) – s-metolachlor
  9. 9. Other ways to categorize herbicides • MOA – – – – – PSII = photosynthesis inhibitors HPPD =pigment inhibitors MI =seedling root inhibitors PPO = cell membrane disruptors VLCFA = seedling shoot inhibitors • Contact vs. Systemic • Xylem vs. Phloem Mobile • Chemical Family • SELECTIVITY (especially for PREs)
  10. 10. Herbicide List • list
  11. 11. Photosynthetic Inhibitors (primarily soil-applied) Triazines atrazine (AAtrex) metribuzin (Sencor)
  12. 12. Injury Symptoms of Soil-Applied PSI • Injury symptoms appear after the food reserves in the cotyledons have been exhausted • The injury symptoms will appear first on the oldest leaves of the plant • Since these herbicides move in the water conducting tissue (xylem), injury symptoms will follow the path of water movement in the plant Roots Stem Leaves Leaf margins
  13. 13. Injury Symptoms of Soil-Applied PSI • Injury symptoms appear as a yellowing (chlorosis) of the leaf tissue which, if severe enough, eventually becomes necrotic (dead) tissue • Initial chlorosis appears at the leaf margins as the herbicide follows the same path as water through the plant • Advanced chlorosis of the leaf tissue is interveinal (between the veins) – Veins remain green
  14. 14. Interveinal Chlorosis in cotton
  15. 15. Chlorophyll • Pigments are molecules that absorb light – Sunlight Pigments PS Food • Chlorophyll is the plant pigment responsible for the green color of plants • The synthesis of chlorophyll has many steps, some of which can be inhibited by herbicides • One family of herbicides that block a step in chlorophyll synthesis is the PPO inhibitors http://www.youtube.com/watch?v=zaxH4xeMGzM
  16. 16. Protoporphyrinogen Oxidase Inhibitors • These herbicides inhibit a step in the chlorophyll biosynthesis pathway – protoporphyrinogen oxidase = PPO inhibitors • Blockage of this pathway results in the production of free radicals which damage plant membranes – some refer to this family as the “membrane disruptors” – membrane damage results in characteristic leaf burn • When foliar-applied, these herbicides show limited movement in the plant
  17. 17. Protoporphyrinogen Oxidase Inhibitors N-Phenylphthalimides flumioxazin (Valor) Aryl Triazolinone sulfentrazone (Authority) Pymidinedione saflufenacil (Sharpen, Kixor)
  18. 18. Injury Symptoms of PPO Inhibitors • Soil-applied PPO inhibitors are mobile within the plant • Injury often related to multiple factors – variety, soil pH, tillage, environment • Symptoms often present on cotyledons and hypocotyl, older leaves – reddish lesions – “wrinkled” true leaves
  19. 19. Tim says: chlorotic veins in soybeans and corn for soil applied PPO injury
  20. 20. Carotenoid Synthesis Inhibitors (Bleachers) • Carotenoids are “accessory” plant pigments that protect chlorophyll during photosynthesis – dissipate excess energy from excited chlorophyll molecules • Chlorophyll is the pigment responsible for the green color of plants – chlorophyll reflects the green wavelength of visible light • Carotenoid synthesis inhibitors block the formation of carotenoids – if carotenoids are absent, chlorophyll can be destroyed during PS and plants can lose their green color
  21. 21. Bleachers • Absorbed through roots and shoots, but translocated only in the xylem • Prevents synthesis of pigments that protect chlorophyl • Foliage turns white and appears bleached
  22. 22. Ross is not funny
  23. 23. Carotenoid Synthesis Inhibitors Isoxazalidinones clomazone (Command) Isoxazoles isoxaflutole (Balance)
  24. 24. Injury Symptoms of Carotenoid Synthesis Inhibitors • Corn foliage is white – lack of carotenoids leads to destruction of chlorophyll • Clomazone carryover – corn generally recovers • Isoxaflutole injury – corn does not always recover – formulation change from dry to liquid helped mixing problems – application problems, hybrid sensitivity issues are not resolved by formulation changes
  25. 25. Command Carryover in Oats
  26. 26. Balance Injury, cold wet conditions
  27. 27. Light-activated Herbicides • How bored is everyone/how am I doing on time • Reichers explains as multiple SOAs, but kind of one MOA • PSI, PSII, PPO, HPPD, Glutamine synthetase
  28. 28. Seedling Growth Inhibitors • These herbicides inhibit the growth and development of weed seedlings, usually before the weeds emerge – do not inhibit seed germination • These herbicides include the dinitroanilines, chloroacetamides, and thiocarbamates • These herbicides are absorbed by the roots and shoots of weed seedlings – DNAs and Thiocarbamates - root and shoot – Chloroacetamides - shoot
  29. 29. Cell Reproduction • Cell division (mitosis) is the process by which cells reproduce • During cell division the genetic material (chromosomes) is replicated and distributed evenly to the two new daughter cells • Specialized structures called microtubules function to distribute the genetic material equally to the two new cells
  30. 30. Dinitroaniline Herbicides SoA: Microtubule Inhibition trifluralin (Treflan, others) pendimethalin (Prowl)
  31. 31. Injury Symptoms of DNA Herbicides • Corn seedlings are usually stunted with club-shaped roots and limited secondary root development – characteristic symptom of DNA, also corn nematodes • Foliage often with purple leaf margins, probably attributable to poor phosphorus uptake – limited root growth leads to limited nutrient absorption • Lateral roots of soybeans may be pruned from excessive rates of DNA herbicides. Hypocotyls may swell (callus) and crack, causing lodging late in the season
  32. 32. Chloroacetamide Herbicides • These herbicides inhibit primarily shoot development in susceptible species – root symptoms not common • Primary mechanism of plant death not completely understood – some speculate these herbicides interfere with cell division by inhibiting formation of very long chain fatty acids • Many formulated with safeners to reduce corn injury potential
  33. 33. Chloroacetamides and Thiocarbamates Chloroacetamides S-metolachlor (Dual II Magnum) acetochlor (Harness,TopNotch, etc)
  34. 34. Injury Symptoms of Chloroacetamides • Injury symptoms are most frequent under cool, wet conditions – those conditions that slow corn growth • Corn seedlings may leaf-out underground. Following emergence, leaves may fail to unfurl correctly, and the leaves may appear crinkled – have observed leaf rolling on much taller corn, but is this more herbicide or environment related? • Symptoms typically dissipate when temperatures increase and soils dry
  35. 35. Injury Symptoms of Chloroacetamides • Soybean leaves may also appear crinkled or puckered. A shortened leaf mid-vein gives the leaf a heart-shaped or "draw string" appearance – I think it is hard to differentiate b/n PRE PPO symptomology on soybeans
  36. 36. Buggy Whipping
  37. 37. “Stumble up to a plot” • We talked a lot about how herbicides work and their symptomology • Next step is to put together keys for selectivity of crops and weeds • Looking at plots this summer will help immensely! • Until then “roll over into a plot”
  38. 38. Quiz next week!!!

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