Transcript Herbicide Mode of Action - Montana State University

Herbicide Mode of
Action
Celestine Duncan
Weed Management Services
Mode of Action
Sequence of events from absorption into the plant
until the plant dies
Classification:
1) Plant Growth Regulators
2) Amino Acid Biosysthesis Inhibitors
3) Photosynthesis Inhibitors
4) Growth Inhibitors
5) Pigment Inhibitors
6) Grass Specific herbicides
7) Membrane Disrupters
How many MOA are represented in
this list of herbicides?
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•
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Tordon 22K
Transline
Curtail
Banvel (Clarity)
Garlon
2,4-D
Redeem
?
Range and Pasture
Herbicide MOA
• Plant Growth Regulators
• Amino Acid Biosynthesis
Inhibitors
Plant Growth Regulators (PGR)
 Referred to as synthetic auxins (regulate growth in
plant tissues)
 Accumulation at growing points
 Specific biochemical change responsible for
killing plant is not known (probably several
processes)
 Grasses are not susceptible (may be due to
differences in vascular tissue structure or
differences in translocation or metabolism)
Common Leaf Symptoms from PGR
Exposure
normal
cupped and blistered from
PGR exposure
Foliar PGR Application
short internode
accumulation
In new growth
Root Absorption of
Plant Growth Regulator Herbicides
translocation to
growing point
swollen
hypocotyl
callus formation on roots
lack of root
development
Amino Acid Inhibitors
(Glyphosate, Escort, Plateau)
Prevent synthesis of certain amino acids
produced by plants but not animals.
Translocates to shoot and root new growth
Plants stop growing shortly after application
Plant death may be slow (10 days+)
Plateau or Escort Injury Symptoms
Stunting
Chlorosis of
youngest tissue
Glyphosate (Roundup) Drift
chlorosis
stem proliferation
shortened
internodes