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Herbicide Modes of Action

Herbicide Modes of Action. Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences The University of Georgia. April 2008. Some things to remember…. photosynthesis (food) respiration (energy) amino acids (proteins/growth) lipids (cell membranes)

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Herbicide Modes of Action

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  1. Herbicide Modes of Action Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences The University of Georgia April 2008

  2. Some things to remember…. • photosynthesis (food) • respiration (energy) • amino acids (proteins/growth) • lipids (cell membranes) • pigments (energy/light capture) • chlorophyll, carotenoids • mitosis (cell division)

  3. Mode of Action • the sequence of events that leads to plant death or growth interruption • 2 phases * movement to target site * interaction at target site

  4. Mechanism of Action (Site) • Location at which a herbicide exerts its toxicity at the cellular level • more specific

  5. ACCase Inhibitors • Inhibit acetyl-CoA-carboxylase (ACCase) enzyme • Enzyme needed for fatty acid synthesis • Dim’s and Fop’s • Achieve, Assure, Axial, Fusilade, Poast, Select

  6. “rotted” meristem Source: W. K. Vencill, UGA

  7. ALS Inhibitors • Inhibit acetolactate synthase (ALS) enzyme • enzyme needed to produce certain amino acids (isoleucine, leucine, valine)

  8. Accent Ally/Cimarron Beacon Beyond Cadre Classic Envoke Exceed Express Finesse FirstRate Glean Harmony Extra Maverick Pro Osprey Peak Permit Pursuit Python Scepter Staple Strongarm Commonly Used ALS Herbicides

  9. Cadre “yellow flash” Staple+ on Sorghum

  10. Resolve 25WG (rimsulfuron) Injury to Field Corn Pictures @ 18 DAT 1.0 oz/A Applied PRE

  11. Photosystem II Inhibitors • Inhibit photosynthesis by binding to QB-binding niche on D1 protein • Evik, Caparol, Atrazine, Basagran, Buctril, Direx, Cotoron, Lorox, Sencor, Simazine

  12. Bladex Cotoran Source: W. K. Vencill, UGA

  13. Photosystem I Inhibitors • Accept electrons from PSI to form radicals • Super radicals formed to create peroxides • Diquat, paraquat

  14. Paraquat Source: Purdue University

  15. PPO Inhibiting Herbicides • PPO or Protox • Protoporphyrinogen oxidase • Enzyme found in chloroplast and mitochondria needed for formation of chlorophyll • Cell membrane destruction • Many common herbicides have this mode of action!! • Ultra Blazer, Cobra, Goal, Reflex, Ronstar, Resource, Aim, Valor, Storm, Spartan, ET

  16. Valor Injury on Peanut Blazer Injury on Peanut Cobra on Soybeans

  17. Carotenoid Biosynthesis Inhibitors • Inhibit phytoene desaturase (PDS) or hydroxyphenyl pyruvate dioxygenase (HPPD) • Command, Callisto, Laudis, Solicam/Zorial, Impact

  18. Command Zorial Laudis

  19. EPSP Synthase Inhibitor • EPSP synthase needed for production of certain amino acids (tryptophan, tyrosine, and phenylalanine) • glyphosate

  20. Source: Purdue University Weed Science Source: MSU Weed Science

  21. Glutamine Synthetase Inhibitors • Glutamine synthetase converts glutamate and ammonia to glutamine • Causes ammonia accumulation in plants • Liberty, Ignite

  22. Source: University of Missouri Weed Science

  23. Mitosis Inhibitors • Microtubule inhibition • Treflan, Prowl, Sonalan, Surflan, Dacthal • Inhibition of very long-chain fatty acids • Dual Magnum, Outlook, Intrro

  24. Prowl Injury on Corn

  25. Dual Injury Source: University of Wisconsin Weed Science

  26. Fatty Acid and Lipid Biosynthesis Inhibitors • Inhibition of lipid synthesis (not ACCase) • Prefar, Sutan, Eptam, Eradicane, Ordram, Tillam, Bolero

  27. Source: Purdue University Weed Science Source: UC-Davis Weed Science

  28. Synthetic Auxins • Disrupt hormonal balance • 2,4-D, Banvel, Clarity, Status, Stinger, MCPA, Facet, Remedy, Grazon P+D

  29. Source: Purdue University Weed Science Source: Purdue University Weed Science

  30. Unknown MOA • DSMA, MSMA • Cell membrane destruction???

  31. MSMA on Peanut MSMA on Zoysia

  32. UGA Weed Science www.gaweed.com

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