Transcript Mechanism of Activit..

“Herbicides and Their
Mechanisms of Action”
Integrated Pest Management &
Certification Training
Richard D. Lee
IPM Specialist
USDI-BLM
Journey in Time

20 companies
1984:
Cyanamid
Miles
Dow
Stauffer
ICI Americas
Monsanto
Union Carbide
Rohm & Haas
Zoecon
FMC
BASF
Eli Lilly
DuPont
Shell
CIBA-Geigy
Nor-AM
Hoechst
Velsicol
ISK Biotech
Ortho
Journey in Time

Early 2002:
Syngenta
Bayer
BASF
Dow AgroSciences
DuPont
Valent
Monsanto
FMC
8 companies
Active Ingredients Approved
for Use on BLM






Atrazine
Bromacil
Chlorsulfuron
Clopyralid
2,4-D
Dicamba

Diuron
Fosamine
Ammonium
Glyphosate

Hexazinone


AAtrex Nine-O
Hyvar ®
Telar ®
Transline ®
various
Clarity ®
Vanquish ®
Karmex ®
Krenite ®
Roundup Pro ®
AquaMaster ®
Velpar L ®
®
Syngenta
DuPont
DuPont
Dow AgroSci.
several
BASF
Syngenta
Griffin
DuPont
Monsanto
Monsanto
DuPont
Active Ingredients Approved
for Use on BLM

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




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
Imazapyr
Imazapic
Mefluidide
Metsulfuron
methyl
Picloram
Simazine
Sulfometuron
methyl
Tebuthiuron
Triclopyr
Arsenal ®
Plateau ®
Embark ®
BASF
BASF
PBI Gordon
Escort XP ®
Tordon 22K ®
Princep ®
DuPont
Dow AgroSci.
Syngenta
Oust XP ®
Spike 20P ®
Garlon 3A, 4
DuPont
Dow AgroSci.
Dow AgroSci.
®
Classification of Herbicides

Application Method

Foliar Applied
• Plant contact

Soil Applied
• Soil contact

Broadcast
• Entire area

Spot
• Specified area
Classification of Herbicides

Application Timing

Preemergence
• Prior to seed
germination

Postemergence
• After seed
germination and
active growth

Post-directed
• Directed to
particular portion of
plant once emerged
and growing
Classification of Herbicides

Plant/Soil
Environment

Selectivity
• Selective vs
nonselective

Systemic
• Mobile vs nonmobile in the plant

Residual Activity
• Extended vs nonextended soil
activity
Classification of Herbicides

Formulation

Liquid
• Solution
• Emulsifiable conc.
• Flowable

Dry
•
•
•
•
Soluble powder
Wettable powder
Dry flowable
Granular
Classification of Herbicides

Mechanism of
Activity

“Why You See What
You See When You
See”
Focus of the discussion

Lets take some
time discussing
how herbicides kill
their target and
what it looks like.
What To Do If Herbicide
Injury is Suspected.

1. Seek background information.


History of the area.
2. Evaluate what is seen.
Look at the roots.
 Loot at the stems.
 Look at the leaves.


Consider all possible options or
situations.
What To Do If Herbicide
Injury is Suspected.

Identify possible source.
Off-target movement.
 Wrong herbicide.
 Improper Application.
 Other options/ideas???

Herbicide Behavior in Plants

To understand
herbicide injury
we need to
understand the
ways in which
herbicides do
their job.
Remember!!!!
“Herbicide injury, in
most cases, is the
result of the
herbicide, doing
what it was
designed to do, in
the wrong place at
the wrong time.”
Active Ingredients Approved
for Use on BLM






Atrazine
Bromacil
Chlorsulfuron
Clopyralid
2,4-D
Dicamba

Diuron
Fosamine
Ammonium
Glyphosate

Hexazinone


AAtrex Nine-O
Hyvar ®
Telar ®
Transline ®
various
Clarity ®
Vanquish ®
Karmex ®
Krenite ®
Roundup Pro ®
AquaMaster ®
Velpar L ®
®
Syngenta
DuPont
DuPont
Dow AgroSci.
several
BASF
Syngenta
Griffin
DuPont
Monsanto
Monsanto
DuPont
Active Ingredients Approved
for Use on BLM









Imazapyr
Imazapic
Mefluidide
Metsulfuron
methyl
Picloram
Simazine
Sulfometuron
methyl
Tebuthiuron
Triclopyr
Arsenal ®
Plateau ®
Embark ®
BASF
BASF
PBI Gordon
Escort XP ®
Tordon 22K ®
Princep ®
DuPont
Dow AgroSci.
Syngenta
Oust XP ®
Spike 20P ®
Garlon 3A, 4
DuPont
Dow AgroSci.
Dow AgroSci.
®
Types of Herbicide Injury
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1.
2.
3.
4.
5.
6.
7.
8.
Plant Growth Regulation
Photosynthesis Inhibitors
Photosynthetic Pigment Inhibitors
Plant Growth Inhibitors
Amino Acid Synthesis Inhibition
Lipid Biosynthesis Inhibition
Cell Membrane Disruption
Unclassified Activity
Active Ingredients Approved
for Use on BLM










Atrazine
Bromacil
Chlorsulfuron
Clopyralid
2,4-D
Dicamba
Diuron
Fosamine
Ammonium
Glyphosate
Hexazinone
Photosynthetic Inhibitor
Photosynthetic Inhibitor
Amino Acid Biosynthesis
Plant Growth Regulator
Plant Growth Regulator
Plant Growth Regulator
Photosynthetic Inhibitor
Plant Growth Regulator
Amino Acid Biosynthesis
Photosynthetic Inhibitor
Active Ingredients Approved
for Use on BLM









Imazapyr
Imazapic
Mefluidide
Metsulfuron
methyl
Picloram
Simazine
Sulfometuron
methyl
Tebuthiuron
Triclopyr
Amino Acid Biosynthesis
Amino Acid Biosynthesis
Plant Growth Regulator
Amino Acid Biosynthesis
Plant Growth Regulator
Photosynthetic Inhibitor
Amino Acid Biosynthesis
Photosynthetic Inhibitor
Plant Growth Regulator
Types of Herbicide Injury
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1.
2.
3.
4.
5.
6.
7.
8.
Plant Growth Regulation
Photosynthesis Inhibitors
Photosynthetic Pigment Inhibitors
Plant Growth Inhibitors
Amino Acid Synthesis Inhibition
Lipid Biosynthesis Inhibition
Cell Membrane Disruption
Unclassified Activity
Mechanism of Action &
Herbicides Used

Plant Growth
Regulating
Herbicides
Plant Growth Regulation




Activity is similar to that of IAA.
Addition of “synthetic IAA” results in an
imbalance of the growth regulating
hormone.
Cells of the leaf vein rapidly divide while
cells between the veins do not.
Cell division and respiration increase,
while photosynthesis does not.
Plant Growth Regulation

What are you going to see visually?
1. Strap-like leaves - parallel veins in
the leaves.
 2. Downward twisting and cupping of
the leaves.
 3. Excessive adventitious root
formation will be stimulated upon
root contact.

Plant Growth Regulation
Inter-venal Cells Do Not Divide
Leaf Vein Cell Divide
Plant Growth Regulation

Examples include:

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2,4-D
Dicamba
Picloram
Clopyralid
Triclopyr
How does this type of injury
occur?
Drift - both particle and vapor.
 Improper cleaning of equipment.
 Applying when air temperatures
exceed those listed on the label.
 Exceeding the labelled rate.

Mechanism of Action &
Herbicides Used

Photosynthetic
Inhibiting
Herbicides
Photosynthesis Inhibitors
The photosynthetic process is shut
down.
 Generally applied to the soil, moves
through the plant in the xylem
system.
 Foliage and stems are affected, yet
the root system is not.

Photosynthesis Inhibitors

Plants exposed to treated soil will
germinate and emerge, take up the
herbicide and move it to the leaves
where it will result in injury.
Photosynthesis Inhibitors

What are you going to see visually?
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
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1. Plants turn yellow and die as a result of
chlorophyll breakdown.
2. As the injury proceeds, the plant will
turn brown and die from the bottom of
the plant to the top of the plant.
3. Leaves initially turn yellow between the
veins, dying from the tip towards the
base, and from the outer edge to the
center.
Photosynthesis Inhibitors
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Examples Include:
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Atrazine
Bromacil
Diuron
Hexazinone
Simazine
Tebuthiuron
How does this type of injury
occur?
Movement of treated soil - these
herbicides are residual.
 Lack of incorporation into the soil.
 Applying in an area where the root
system of desirable plants can take
up the herbicide.
 NOT READING THE LABEL.
 Failing to understand the residual
capability of these herbicides.

Mechanism of Action &
Herbicides Used

Amino Acid
Synthesis
Inhibiting
Herbicides
Amino Acid Synthesis
Inhibition


Injury is associated with a particular
enzyme, which, in turn, is associated with
a particular amino acid process.
Visual results are the result of secondary
injury – the injury as the beginning of a
chain of events that take place in the
plant.

This is why the visual symptoms take time to
develop – it is not an immediate process.
Amino Acid Synthesis
Inhibition
Amino Acid Synthesis
Inhibition


May or may not have soil activity.
Activity associated with a particular
amino acid synthesis sequence.

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Acetyl CoA Carboxylase (ACCase) - Select
Acetolacte Synthase (ALS) - Arsenal, Escort
EPSPase Inhibitor - Roundup
Interference is translated to protein
synthesis and inhibition of growth which
takes time - slow acting.
Amino Acid Synthesis
Inhibition

What are you going to see visually?
Initially there will be a general
yellowing of the treated plants.
 After 5 to 10 days, chlorosis results in
necrosis.

Amino Acid Synthesis
Inhibition

Imidazolinones





Arsenal
Plateau
Sahara
Top Site
Glyphosate

Roundup

Sulfonylureas



Escort
Oust
Telar
How does this type of injury
occur?



Drift - application on a windy day.
Movement of treated soil.
Failure to apply the correct amount – the
use rates are small and an error in
measuring can make a large difference.
Summary Ideas

By taking time to
learn about the visual
symptoms associated
with the different
classes of herbicides you can more easily
understand what you
see, when you see it.
Summary

Just Remember:

“Worrying has killed more
people than work
because more people
worry than work.”