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

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Presentation on theme: "Herbicide Modes of Action Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences The University of Georgia April 2008."— Presentation transcript:

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) photosynthesis (food) respiration (energy) respiration (energy) amino acids (proteins/growth) amino acids (proteins/growth) lipids (cell membranes) lipids (cell membranes) pigments (energy/light capture) pigments (energy/light capture) chlorophyll, carotenoidschlorophyll, carotenoids mitosis (cell division) mitosis (cell division)

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

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

5 ACCase Inhibitors Inhibit acetyl-CoA-carboxylase (ACCase) enzyme Inhibit acetyl-CoA-carboxylase (ACCase) enzyme Enzyme needed for fatty acid synthesis Enzyme needed for fatty acid synthesis Dims and Fops Dims and Fops Achieve, Assure, Axial, Fusilade, Poast, Select Achieve, Assure, Axial, Fusilade, Poast, Select

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

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

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

9 Cadre yellow flash Staple+ on Sorghum

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

11 Photosystem II Inhibitors Inhibit photosynthesis by binding to Q B -binding niche on D1 protein Inhibit photosynthesis by binding to Q B -binding niche on D1 protein Evik, Caparol, Atrazine, Basagran, Buctril, Direx, Cotoron, Lorox, Sencor, Simazine 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 Accept electrons from PSI to form radicals Super radicals formed to create peroxides Super radicals formed to create peroxides Diquat, paraquat Diquat, paraquat

14 Paraquat Source: Purdue University

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

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

17 Carotenoid Biosynthesis Inhibitors Inhibit phytoene desaturase (PDS) or hydroxyphenyl pyruvate dioxygenase (HPPD) Inhibit phytoene desaturase (PDS) or hydroxyphenyl pyruvate dioxygenase (HPPD) Command, Callisto, Laudis, Solicam/Zorial, Impact 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) EPSP synthase needed for production of certain amino acids (tryptophan, tyrosine, and phenylalanine) glyphosate glyphosate

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

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

22 Source: University of Missouri Weed Science

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

24 Prowl Injury on Corn

25 Source: University of Wisconsin Weed Science Dual Injury

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

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

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

29 Source: Purdue University Weed Science

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

31 MSMA on Peanut MSMA on Zoysia

32 UGA Weed Science


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