Herbicide Modes of Action Herbicide Modes of Action Eric P. Prostko - - PowerPoint PPT Presentation

Herbicide Modes of Action Herbicide Modes of Action

Eric P. Prostko Eric P. Prostko Extension Weed Specialist Extension Weed Specialist Department of Crop & Soil Sciences Department of Crop & Soil Sciences The University of Georgia The University of Georgia

April 2008

Some things to remember…. Some things to remember….

• photosynthesis

photosynthesis (food) (food)

• respiration

respiration (energy) (energy)

• amino acids

amino acids (proteins/growth) (proteins/growth)

• lipids

lipids (cell membranes) (cell membranes)

• pigments

pigments (energy/light capture) (energy/light capture)

• chlorophyll, carotenoids

chlorophyll, carotenoids

• mitosis

mitosis (cell division) (cell division)

Mode of Action Mode of Action

• the sequence of events that leads to

the sequence of events that leads to plant death or growth interruption 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

Mechanism of Action (Site) Mechanism of Action (Site)

• Location at which a herbicide exerts

Location at which a herbicide exerts its toxicity at the cellular level its toxicity at the cellular level

• more specific

more specific

ACCase Inhibitors ACCase Inhibitors

• Inhibit acetyl

Inhibit acetyl-

• CoA

CoA-

• carboxylase

carboxylase (ACCase) enzyme (ACCase) enzyme

• Enzyme needed for fatty acid

Enzyme needed for fatty acid synthesis synthesis

• Dim’s and Fop’s

Dim’s and Fop’s

• Achieve, Assure, Axial, Fusilade,

Achieve, Assure, Axial, Fusilade, Poast, Select Poast, Select

“rotted” meristem

Source: W. K. Vencill, UGA

ALS Inhibitors ALS Inhibitors

• Inhibit acetolactate synthase (ALS)

Inhibit acetolactate synthase (ALS) enzyme enzyme

• enzyme needed to produce certain

enzyme needed to produce certain amino acids (isoleucine, leucine, amino acids (isoleucine, leucine, valine) valine)

Commonly Used ALS Herbicides 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
• 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

FirstRate Strongarm

Cadre “yellow flash” Cadre “yellow flash” Staple+ on Sorghum Staple+ on Sorghum

Resolve 25WG (rimsulfuron) Injury Resolve 25WG (rimsulfuron) Injury to Field Corn to Field Corn

Pictures @ 18 DAT

1.0 oz/A Applied PRE

Photosystem II Inhibitors Photosystem II Inhibitors

• Inhibit photosynthesis by binding to

Inhibit photosynthesis by binding to Q QB

B-

• binding niche on D1 protein

binding niche on D1 protein

• Evik, Caparol, Atrazine, Basagran,

Evik, Caparol, Atrazine, Basagran, Buctril, Direx, Cotoron, Lorox, Buctril, Direx, Cotoron, Lorox, Sencor, Simazine Sencor, Simazine

Bladex Bladex Cotoran

Source: W. K. Vencill, UGA

Photosystem I Inhibitors Photosystem I Inhibitors

• Accept electrons from PSI to form

Accept electrons from PSI to form radicals radicals

• Super radicals formed to create

Super radicals formed to create peroxides peroxides

• Diquat, paraquat

Diquat, paraquat

Paraquat Paraquat

Source: Purdue University

PPO Inhibiting Herbicides PPO Inhibiting Herbicides

• PPO or Protox

PPO or Protox

• Protoporphyrinogen

Protoporphyrinogen

• xidase
• xidase
• Enzyme found in

Enzyme found in chloroplast and chloroplast and mitochondria needed for mitochondria needed for formation of chlorophyll formation of chlorophyll

• Cell membrane

Cell membrane destruction destruction

• Many common herbicides

Many common herbicides have this mode of action!! have this mode of action!!

• Ultra Blazer, Cobra, Goal

Ultra Blazer, Cobra, Goal,

,

Reflex, Ronstar, Resource, Reflex, Ronstar, Resource, Aim, Valor, Storm, Spartan, Aim, Valor, Storm, Spartan, ET ET

Blazer Injury on Peanut Blazer Injury on Peanut Valor Injury on Peanut Valor Injury on Peanut

Cobra on Soybeans

Carotenoid Biosynthesis Inhibitors Carotenoid Biosynthesis Inhibitors

• Inhibit phytoene desaturase (PDS)

Inhibit phytoene desaturase (PDS)

• r hydroxyphenyl pyruvate
• r hydroxyphenyl pyruvate

dioxygenase (HPPD) dioxygenase (HPPD)

• Command, Callisto, Laudis,

Command, Callisto, Laudis, Solicam/Zorial, Impact Solicam/Zorial, Impact

Command Zorial Zorial

Laudis

EPSP Synthase Inhibitor EPSP Synthase Inhibitor

• EPSP synthase needed for

EPSP synthase needed for production of certain amino acids production of certain amino acids (tryptophan, tyrosine, and (tryptophan, tyrosine, and phenylalanine) phenylalanine)

• glyphosate

glyphosate

Source: Purdue University Weed Science Source: MSU Weed Science

Glutamine Synthetase Inhibitors Glutamine Synthetase Inhibitors

• Glutamine synthetase converts

Glutamine synthetase converts glutamate and ammonia to glutamate and ammonia to glutamine glutamine

• Causes ammonia accumulation in

Causes ammonia accumulation in plants plants

• Liberty, Ignite

Liberty, Ignite

Source: University of Missouri Weed Science

Mitosis Inhibitors Mitosis Inhibitors

• Microtubule inhibition

Microtubule inhibition

• Treflan, Prowl, Sonalan, Surflan,

Treflan, Prowl, Sonalan, Surflan, Dacthal Dacthal

• Inhibition of very long

Inhibition of very long-

• chain fatty

chain fatty acids acids

• Dual Magnum, Outlook, Intrro

Prowl Injury on Corn

Dual Injury

Source: University of Wisconsin Weed Science

Fatty Acid and Lipid Biosynthesis Fatty Acid and Lipid Biosynthesis Inhibitors Inhibitors

• Inhibition of lipid synthesis (not

Inhibition of lipid synthesis (not ACCase) ACCase)

• Prefar, Sutan, Eptam, Eradicane,

Prefar, Sutan, Eptam, Eradicane, Ordram, Tillam, Bolero Ordram, Tillam, Bolero

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

Synthetic Auxins Synthetic Auxins

• Disrupt hormonal balance

Disrupt hormonal balance

• 2,4

2,4-

• D, Banvel, Clarity, Status,

D, Banvel, Clarity, Status, Stinger, MCPA, Facet, Remedy, Stinger, MCPA, Facet, Remedy, Grazon P+D Grazon P+D

Source: Purdue University Weed Science Source: Purdue University Weed Science

Unknown MOA Unknown MOA

• DSMA, MSMA

DSMA, MSMA

• Cell membrane destruction???

Cell membrane destruction???

MSMA on Peanut MSMA on Zoysia

UGA Weed Science UGA Weed Science www.gaweed.com www.gaweed.com