Herbicide Mode of Action Categories
![]() |
|
Agdex#: | 641 |
---|---|
Publication Date: | 05/00 |
Order#: | 00-061 |
Last Reviewed: | 08/09 |
History: | Original Factsheet |
Written by: | Hugh Martin - Program Lead, Organic Crop Production/OMAFRA |
Table of Contents
- Introduction
- Herbicides Causing Injury to New Growth and with the Potential to Move From Leaves to Roots
- Herbicides Causing Injury to Old Growth and With the Potential to Move Only Upward
- Herbicides Applied to the Soil With the Potential to Injure Emerging Seedlings
- Herbicides Causing Immediate Injury With Little or no Movement
- Acknowledgements
Introduction
Herbicides are chemicals with complex chemical structures. While each chemical has unique properties, a family of herbicides has similar chemical structures with many similar characteristics. This Factsheet explains:
- how chemicals are grouped into categories based on their mode or site of action
- some of the plant injury symptoms of chemicals and
- the fate of these herbicides in the soil.
Herbicide half life in soil is given as a typical or average value as listed in the Weed Science Society of America Herbicide Handbook. These values vary depending on environmental conditions and soil type.
Herbicides Causing Injury to New Growth and With the Potential to Move From Leaves to Roots
Lipid Synthesis (ACCase) Inhibitors
Site of Action Group 1
Inhibitors of acetyl CoA carboxylase (ACCase) also known as "Grass Growing Point Disintegrators"
Plant Injury Symptoms
- Aryloxyphenoxyproprionates (phloem mobile): Injury on grass plants only. All are systemic but diclofop and fenoxaprop are less mobile and do not control perennial grasses. Newer leaf tissue will be yellow (chlorotic) or brown (necrotic) and the leaves in the whorl be easily pulled out. Symptoms develop slowly. Prone to resistance development.
- Cyclohexanediones (systemic): Same as for the aryloxyphenoxyproprionates.
Herbicide Breakdown
- Aryloxyphenoxyproprionates: Most herbicides in this category
are broken down by microbial action. Anaerobic conditions may
delay breakdown. Low mobility in soil. Little or no soil activity.
- Half life in soil:
- fenoxaprop - 9 days (aerobic conditions), 30 days (anaerobic)
- fluazifop - 15 days
- diclofop - 30 days at pH 7.0
- quizalofop - 60 days
- Half life in soil:
- Cyclohexanediones: Most herbicides in this category are broken
down by microbial action. These herbicides are generally non-persistent
in soils.
- Half life in soil:
- clethodim - 3 days
- sethoxydim - 5 days
Table 1. ACCase Inhibitors
Aryloxyphenoxyproprionates (Group 1)2 "fops" Trade1 Names Common Names HOEGRASS diclofop-methyl ACCLAIM SUPER fenoxaprop-p-ethyl EXCEL SUPER fenoxaprop-p-ethyl FUSILADE II fluazifop-p-butyl VENTURE fluazifop-p-butyl ASSURE II quizalofop-p-ethyl
Cyclohexanediones (Group 1) "dims" Trade1 Names Common Names SELECT clethodim POAST ULTRA sethoxydim ACHIEVE tralkoxydim 1 Herbicide Trade names are in capitals and common names are in lower case in all tables.
2 The site of action group numbers are shown in brackets (as established by the Weed Science Society of America).
Amino Acid Synthesis Inhibitors; Branch Chain Amino Acid Inhibitors
Site of Action Group 2
Inhibitors of acetolactase synthase (ALS) and also called acetohydroxyacid synthase (AHAS)
Plant Injury Symptoms
- Imidazolinones (phloem mobile): Also referred to as "imi" herbicides. Grass plants may be stunted with interveinal yellowing (chlorosis) or purpling. Corn plants may be stunted and show root pruning or stunting. Leaves emerging from the whorl may be yellow to translucent in appearance. Broadleaf plants may be stunted and chlorotic or purple. Leaves may be yellow in appearance and leaf veination may appear red or purple in colour. Symptoms take 1-2 weeks to develop. Prone to resistance development.
- Sulfonylureas (phloem mobile): Same symptoms as for the imidazolinones.
- Sulfonanilides (phloem mobile): Sulfonanilides are also known as Triazolopyrimidines or TPS. Same symptoms as for the imidazolinones.
Herbicide Breakdown
- Imidazolinones: These herbicides are broken down primarily by
microbes with very little degradation under anaerobic conditions.
They are strongly bound to soil organic matter. Dry conditions
cause them to be adsorbed to soil particles and wet conditions
cause the herbicide to be free for breakdown and plant uptake.
At soil pH progressively below 6.5 herbicide is more tightly bound
to the soil OM and is unavailable for breakdown. Warm moist soils
above pH 6.5 increase microbial breakdown. Soil mobility is low.
There is more carryover in low pH soil and this can create a recropping
problem for sensitive crops.
- Half life in soil:
- imazamox - 20-30 days,
- imazethapyr - 60-90 days,
- imazapyr - 25-142 days depending on conditions
- Half life in soil:
- Sulfonylureas: Primarily broken down by hydrolysis and microbes.
SU herbicides are more tightly adsorbed to soil particles and
soil OM at low pH. SU herbicides carryover more in higher pH soils
since acid hydrolysis ceases at high pH levels. The rate of hydrolysis
is greatest at pH below 6.8 and as the temperature increases.
Variable pH across a field can greatly affect the ability of a
herbicide to persist in the soil. More carryover in high pH soil.
- Half life in soil:
- triflusulfuron - 2-4 days
- tribenuron - 10 days
- prosulfuron - 10 days
- thifensulfuron - 12 days
- ethametsulfuron - ? days
- foransulam - ? days
- nicosulfuron - 21 days
- triflusulfuron - 2-4 days
- primisulfuron - 30 days
- chlorsulfuron - 40 days
- chlorimuron - 40 days (more at high pH)
- Half life in soil:
- Triazolopyrimidine Sulfonanilides (TPS): Primarily degraded
by microbes. Activity and degradation increases as the soil pH
increases. Degradation increases in soils with high pH because
in high pH soils the chemical is not adsorbed and are available
for plant uptake and microbial breakdown. All factors that increase
microbial activity also increase herbicide degradation. More carryover
in low pH soils. Recropping to sensitive species can be a problem
with some products.
- Half life in soil:
- cloransulam 8-10 days
- flumetsulam: 1-3 months, less at higher pH)
- Half life in soil:
Table 2. ALS Inhibitors
Imidazolinones (Group 2) Trade Names Common Names VIPER1 imazamox MERIDAN2 imazamox ARSENAL imazapyr PURSUIT imazethapyr PATRIOT2 imazethapyr CLEANSWEEP2 imazethapyr CONQUEST2 imazethapyr
Sulfonylureas (Group s) Trade Names Common Names CLASSIC chlorimuron TELAR chlorsulfuron MUSTER ethametsulfuron-methyl ACCENT nicosulfuron ULTIM nicosulfuron/rimsulfuron BEACON primisulfuron PEAK3 prosulfuron ELIM rimsulfuron PRISM rimsulfuron PINNACLE thifensulfuron REFINE EXTRA thifensulfuron-methyl/tribenuron-methyl UPBEET triflusulfuron-methyl
Sulfonanilides (Group 2) Trade Names Common Names FIRST RATE** cloransulam** BROADSTRIKE DUAL flumetsulam4 BROADSTRIKE TREFLAN flumetsulam4 FIELDSTAR flumetsulam4 STRIKER flumetsulam4 not determined foramsulam** ** currently in testing, proposed names, not currently registered for use in Canada (as of June, 2000)
1 Viper and Meridan are sold as co-packs containing imazamox and fomesafen (Reflex) or bentazon (Basagran Forte)
2 Patriot is sold as a premix containing imazethapyr and atrazine; Cleansweep and Conquest are sold as co-packs containing imazethapyr and bentazon (Basagran Forte) or metribuzin respectively.
3 Peak is sold as a co-pack containing prosulfuron (Peak) and dicamba (Banvel II)
4 Each of the flumetsulam products contain other active ingredients.
Aromatic Amino Acid Synthesis Inhibitors
Amino Acid Derivatives (Glycines) - Site of Action Group 9
Inhibitors of 5-enolpyruvylshikimimate-3-phosphate synthase (EPSPS)
Plant Injury Symptoms
- Aromatic Amino Acid Inhibitors (EPSP synthase) (phloem mobile): One of the most "translocatable" herbicides known. Plant foliage will first yellow (new leaves first) and then turn brown and die within 10-14 days after herbicide application. Resistance has been found but is not yet a problem.
Herbicide Breakdown
- Glyphosate is rapidly and tightly adsorbed to soil. There is
no soil activity due to rapid adsorption. Degradation is by microbial
action and rates vary with soil and microbial population. The
long-term degradative process is not apparent in the field in
terms of bioavailability due to its strong adsorption to soil
particles.
- Half life in soil: glyphosate - 47 days
Table 3. Amino Acid Derivatives
Glycines (Group 9) Trade Names Common Names CREDIT glyphosate IPA1 GLYFOS glyphosate IPA ROUNDUP*** glyphosate IPA VANTAGE*** glyphosate IPA VISION*** glyphosate IPA TOUCHDOWN*** glyphosate TMS2 *** Various products and formulations available
1 IPA is the isopropylamine salt of glyphosate
2 TMS is the trimethylsulfonium salt of glyphosate also known as sulfosate
Auxinic Herbicides (Growth Regulators)
Site of Action Group 4
Synthetic auxins, specific site(s) unknown.
Plant Injury Symptoms
- Phenoxy acids (highly phloem mobile): Broadleaf plants exhibit stem twisting and leaf malformations (cupping, crinkling, parallel veins, leaf strapping). Corn plants exhibit rolled leaves (onion leafing), fused brace roots, stalk bending (goosenecking) and brittleness, and missing kernels. Small grains exhibit twisted flag leaves, sterile florets, or multiple florets, twisted awns and head malformation. Resistance may occur but is not yet a problem.
- Benzoic acids (highly phloem mobile): Dicamba injury is similar to that caused by phenoxy acid herbicides but broadleaf plants may exhibit more cupping than strapping of leaf tissues. May cause more goosenecking in corn and lodging in small grain (especially wheat) than phenoxys. Resistance may occur but is not yet a problem.
- Pyridine acids (highly phloem mobile): Pyridines are also known as Carboxylic acids. Injury similar to phenoxy acid herbicides. Resistance may occur but is not yet a problem.
Table 4. Auxinic Herbicides
Phenoxy acids (Group 4) Trade Names Common Names various *** 2,4-D ESTAMINE 2,4-D ESTASOL 2,4-D various *** 2,4-DB CALIBER 2,4-DB COBUTOX 2,4-DB EMBUTOX 2,4-DB various *** dichlorprop various *** MCPA various *** MCPB CLOVITOX PLUS MCPB /MCPA TROPOTOX PLUS MCPB /MCPA various *** mecoprop
Benzoic Acids (Group 4) Trade Names Common Names BANVEL II dicamba CADENCE dicamba DISTINCT1 dicamba various *** dicamba
Pyridine acids (Group 4) Trade Names Common Names LONTREL clopyralid TRANSLINE clopyralid FIELDSTAR2 clopyralid STRIKER2 clopyralid TORDON picloram GARLON triclopyr *** Various products and formulations available
1 Distinct also contains diflufenzopyr which is an auxin transport inhibitor
2 Fieldstar and Striker also contain flumetsulam
Herbicide Breakdown
- Phenoxy acids Microbial breakdown in warm, moist soils. Rate
of breakdown increases with increased temperature, moisture, pH
and OM content. Potentially mobile, but leaching is minimized
by rapid degradation.
- Half life in soil:
- 2,4-DB - 5 days
- MCPA - 5-6 days
- dichlorprop - 10 days
- 2,4-D - 10 days
- MCPB - 14 days
- mecoprop - 21 days
- Half life in soil:
- Benzoic acids: Breakdown is primarily due to volatization losses
and microbial degradation. Dicamba is highly mobile in soils,
especially on sandy soils but leaching potential is low to medium
due to rapid degradation. Persists longer under conditions of
low rainfall or soil moisture.
- Half life in soil: dicamba - less than 14 days
- Pyridine acids: Degraded by photodegradation and by microbial
breakdown. They are degraded more slowly than the phenoxys or
benzoics. Clopyralid by microbial breakdown only.
- Half life in soil:
- triclopyr - 30 days
- clopyralid - 40 days
- picloram - 90 days
Pigment Inhibitors (Bleaching Herbicides)
- Triazoles (amitrole): Site of Action Group 11 - Inhibitors of carotenoid biosynthesis
- Isoxazolidinones (clomazone): Site of Action Group 13 - Inhibitors of carotenoid biosynthesis
- Isoxazoles (isoxaflutole) and Triketones (mesotrione): Site of Action Group 28 - Inhibitors of p-hydroxyphenyl pyruvate dioxygenase (HPPD).
Table 5. Pigment Inhibitors
Trade Names Common Names AMITROLE (11) amitrole COMMAND (13)** clomazone **
HPPD (Group 28) Trade Names Common Names CONVERGE1 isoxaflutole not determined mesotrione ** ** currently in testing, proposed names, not currently registered for use in Canada (as of June, 2000)
1 Converge is sold as a co-pack containing isoxafluole and atrazine
Plant Injury Symptoms
- Pigment Inhibitors (systemic): Affected plant parts become white to translucent. Susceptible plants may emerge as white plants before dying.
Herbicide Breakdown
- Clomazone breakdown is mostly by microbial with some photodegradation.
Amitrole breakdown is unknown. Isoxaflutole by microbial decomposition.
Not yet known to be prone to resistance.
- Half life in soil:
- amitrole - 14 days
- clomazone - 24 days
- isoxaflutole - 28 days
- Half life in soil:
Herbicides Causing Injury to Old Growth and With the Potential to Move Only Upward
Photosynthesis Inhibitors
- Triazines, Uracils, Phenyl-carbamates, Pyridazinones: Site of Action Group 5 - Inhibitors of photosynthesis at photosystem II, Site A. Blocks electron transport and the transfer of light energy.
- Substituted Ureas: Site of Action Group 7 - Inhibitors of photosynthesis at photosystem II, Site B. Blocks electron transport and the transfer of light energy.
- Others - Benzothiadiazoles (bentazon), Nitriles (bromoxynil), Phenyl-pyridazines (pyridate): Site of Action Group 6 - Inhibitors of photosynthesis at photosystem II, Site A.
Plant Injury Symptoms
- Triazines (xylem mobile): Translocation occurs only in the xylem (upwards only). Injury symptoms occur after the cotyledons and first true leaves emerge. Injury symptoms include yellowing of the leaf margins or tips and yellowing between the leaf veins in broadleaf plants. Older and larger leaves are affected first. Injured leaf tissue eventually turns brown and dies. There is greater injury on higher pH soils (greater than pH 7.2). Prone to resistance which can be an agronomic problem.
- Substituted Ureas and Uracils (xylem mobile): Symptoms are the same as for triazines. Generally not prone to resistance, but it has been reported with long term repeated use.
- Others - bentazon, bromoxynil, pyridate (contact): Injury is confined to foliage that has come in contact with the herbicide. Low doses of these herbicides mimic classical photosynthesis inhibitors. High doses mimic cell membrane disrupters. Crop oil concentrates and other additives may intensify injury symptoms. Grass plants are generally tolerant to the non-systemic photosynthesis inhibitors.
Table 6. Photosynthesis Inhibitors
Triazines (Group 5) Trade Names Common Names AATREX atrazine various *** atrazine BLADEX cyanazine VELPAR hexazinone SENCOR metribuzin LEXONE metribuzin various *** metribuzin GESAGARD prometryne SIMADEX simazine PRINCEP simazine
Uracils (Group 5) Trade Names Common Names HYVAR bromacil SINBAR terbacil
Phenyl-carbamates (Group 5) Trade Names Common Names BETANEX desmedipham SPIN-AID phenmedipham
Pyridazinones (Group 5) Trade Names Common Names PYRAMIN pyrazon
Others Trade Names Common Names BASAGRAN (6) bentazon PARDNER (6) bromoxynil LENTAGRAN (6) pyridate
Substituted Ureas (Group 7) Trade Names Common Names KARMEX diuron AFOLAN linuron LOROX linuron PATORAN metobromuron AFESIN Monolinuron *** Various products and formulations available
Herbicide Breakdown
- Triazines: Breakdown is mainly by microbial action but hydrolysis
is the major contributer to breakdown at low pH. More available
on sandy soils due to fewer adsorption sites and warmer temperatures.
Persistence is greater under dry conditions, cold temperatures
and in sandy soils. Persistence is also greater in soils with
low organic matter, low clay content, and higher pH. Recropping
can be a problem with sensitive species.
- Half life in soil:
- cyanazine - 14 days
- metribuzin - 30-60 days
- atrazine - 60 days
- prometryne - 60 days
- simazine - 60 days
- hexazinone - 90 days
- Half life in soil:
- Substituted Ureas and Uracils: Microbial breakdown is primary
means of dissipation.
- Half life in soil:
- metobromuron - 30 days
- monolinuron - 45-60 days
- linuron - 60 days
- bromacil - 60 days
- diuron - 90 days
- terbacil - 120 days
- Half life in soil:
- Others - bentazon, bromoxynil, pyridate: Mainly by microbial
breakdown.
- Half life in soil:
- bromoxynil - 7 days
- pyridate - 7-21 days
- bentazon - 20 days
- pyrazon - 21 days
- phenmedipham - 25-30 days
- desmedipham - <30 days
Herbicides Applied to the Soil With the Potential to Injure Emerging Seedlings
Seedling (or Cell) Growth Inhibitors
- Dinitroanalines and Pyridines (dithiopyr): Site of Action Group 3 - Microtubule assembly inhibitors, tubulin protein involved in cell division, interrupts mitosis (root inhibitors).
- Carbamothioates and Phosphorodithioates: Site of Action Group 8 - Conjugation of acetyl co-enzyme A, specific site unknown (shoot inhibitors).
- Chloroacetamides and Acetamides: Site of Action Group 15 - Conjugation of acetyl co-enzyme A, specific site unknown (shoot inhibitors).
Plant Injury Symptoms
- Dinitroanalines: Injury symptoms include stunted plants that do not fully emerge from the soil and short, thick, lateral roots. Grass (including corn) shoots are short and thick and may appear red or purple in colour. Broadleaf plants may have swollen and cracked hypocotyls (area below cotyledons). There is very little movement of these herbicides within the plant. Some resistance issues.
- Chloroacetamides (xylem mobile only): Symptoms include stunting of shoots that result in abnormal seedlings that do not emerge from the soil. Grasses may leaf-out under ground and the shoots may be abnormal when leaves do not properly unfurl. Broadleaves may have crinkled leaves and or a shortened mid-vein which produces a "draw-string effect" or "heart shaped" leaves. Not prone to resistance.
- Carbamothioates (xylem mobile only): Carbamothioates are also known as thiocarbamates. Shoots are stunted and emerge poorly from the soil. Grasses may fail to emerge from the coleoptile or may leaf-out underground. Leaf tips may not unfurl from the coleoptile creating a "buggy whip" effect. Broadleaves may have crinkled or puckered leaves or the buds may not open. Not prone to resistance.
Table 7. Seedling Growth Inhibitors
Dinitroanalines (Group 3) Trade Names Common Names EDGE ethalfluralin PROWL pendimethalin BONANZA trifluralin RIVAL trifluralin TREFLAN trifluralin
Pyridine (Group 3) Trade Names Common Names DIMENSION dithiopyr
Carbamothioates (Group 8) Trade Names Common Names SUTAN butylate RO-NEET cycloate ERADICANE EPTC EPTAM EPTC AVADEX triallate
Phosphorodithioates (Group 8) Trade Names Common Names BETASAN bensulide
Chloroacetamides (Group 15) Trade Names Common Names FRONTIER dimethenamide AXIOM1 flufenacet DUAL metolachlor
Acetamides (Group 15) Trade Names Common Names DEVRINOL Napropamide 1 Axiom contains both flufenacet and metribuzin
Herbicide Breakdown
- Dinitroanalines: Breakdown by photodegradation and soil microbes.
Soil incorporation is usually required with these products. Microbial
degradation is more rapid under anaerobic conditions. Persistence
is longer under cool, dry conditions. Enhanced degradation ("history
soils") may occur where microbes can rapidly breakdown herbicide
to reduce efficacy.
- Half life in soil:
- dithiopyr - 17 days
- pendimethalin - 44 days
- trifluralin - 45 days
- ethalfluralin - 60 days
- Half life in soil:
- Chloroacetamides: Mainly by microbial degradation. Longer persistence
under anaerobic and cooler conditions.
- Half life in soil:
- dimethenamide - 20 days
- metolachlor - 30-50 days
- flufenacet - 45-60 days
- napropramide - 70 days
- Half life in soil:
- Carbamothioates: Metabolized by soil microbes. Enhanced degradation
("history soils") may occur after repeated applications
where microbes can rapidly breakdown herbicide thereby reducing
efficacy. Soil incorporation is usually required with these products.
- Half life in soil:
- EPTC - 6 days
- butylate - 13 days
- cycloate - 30 days
- triallate - 82 days
- bensulide - 120 days
Herbicides Causing Immediate Injury With Little or no Movement
Cell Membrane Disruptes (Contact Herbicides)
- Phosphorylated Amino Acids (also known as Phosphinic Acids): Site of Action Group 10 - Inhibitors of glutamine synthetase, also known as inhibitors of ammonia assimilation
- Diphenylethers and Oxadiazoles: Site of Action Group 14 - Inhibitors of protoporphyrinogen oxidase (PPO or Protox)
- Bipyridiliums: Site of Action Group 22 - Photosystem I - electron diverters
Plant Injury Symptoms
- Phosphorylated Amino Acids (contact with limited phloem/xylem mobility): Chlorosis and wilting usually occur within 3-5 days followed by necrosis within 1-2 weeks. Symptoms occur faster in bright sunlight and high humidity. Not prone to resistance.
- Bipyridiliums (contact): Plant leaves will have a limp, water soaked appearance, which is followed by browning of the leaf tissue. Drift injury appears as speckling on leaf tissue.
- Diphenylethers (contact): Plant leaves turn yellow then brown and die. Reddish-colored spotting on the leaf surface may appear shortly after application. Plants that do not die may be stunted for a week or so. Crop oils and other additives may increase plant injury. Not prone to resistance.
- Oxadiazoles (contact): Seedlings emerge from treated soil and then wilt and die. Foliar applications cause chlorosis and die within 1-2 days. Not prone to resistance.
Herbicide Breakdown
- Phosphorylated Amino Acids: Rapidly degraded by soil microbes.
- Half life in soil:
- glufosinate - 7 days
- Half life in soil:
- Diphenylethers: Both photo and microbial degradation. Fomesafen
degrades faster under anaerobic conditions.
- Half life in soil:
- aciflurofen - 14-60 days
- oxyfluorfen - 35 days
- fomesafen - 100 days
- Half life in soil:
- Bipyridiliums: Strongly adsorbed to clay particles. Not available
for plant uptake or microbial breakdown.
- Half life in soil:
- difenzoquat - <4 weeks
- diquat - 1000 days
- paraquat - 1000 days
- Half life in soil:
- Oxadiazoles (contact): Strongly adsorbed by soil colloids.
- Half life in soil:
- oxydiazon - 60 days
Table 8. Cell Membrane Disrupters
Phosphorylated Amino Acid (Group 10) Trade Names Common Names IGNITE Glufosinate ammonium LIBERTY Glufosinate ammonium
Diphenylethers (Group 14) Trade Names Common Names BLAZER aciflurofen REFLEX fomesafen GOAL oxyfluorfen
Oxadiazoles (Group 14) Trade Names Common Names RONSTAR oxydiazon
Bipyridiliums (Group 22) Trade Names Common Names AVENGE difenzoquat GRAMOXONE paraquat REGLONE diquat Other Herbicides
- Casoron (xylem mobile): Site of Action Group 20 - chemical family Nitriles, mode of action is the inhibition of cell wall (cellulose) synthesis. Blocks electron transport and the transfer of light energy. Diclobenil is a systemic herbicide and when soil applied susceptible seedlings usually do not emerge.
- Avenge - difenzoquat (xylem mobile): Site of Action Group 8 - chemical family Pyrazolium, mode of action is largely unknown.
- Injury symptoms of chlorosis and necrosis appear within 3-7 days. Some resistant species but not a wide spread agronomic problem.
- Half life in soil:
- difenzoquat - <4 weeks
- Alanap - napthalam: Site of action Group 19 - chemical family Phthalamates, mode of action is the inhibition of auxin transport. Movement within the plant is somewhat limited.
- Injury Symptoms - Strong epinasty and antigeotropic response, abolishing the normal curvature of roots toward the ground and of shoots toward light.
- Microbial breakdown
- Half life in soil:
- napthalam - 14 days
- Half life in soil:
Acknowledgements
Thanks to Dr. J.C. Hall, Department of Environmental Biology, University of Guelph, for his comments on this Factsheet.
Resources
Herbicide Mode of Action and Injury Symptoms, Jeffery L. Gunsolus and William S. Curran, North Central Regional Publication 377, 1994.
Herbicide Mode of Action and Injury Symptoms, CD-ROM, Jeffery L. Gunsolus et al, University of Minnesota Extension Service, 1999
Herbicide Mode-of-Action Categories by Merrill A. Ross and Thomas N. Jordan, Purdue University, 1999.
Classification of Herbicides According to Mode of Action, April 1999, Robert Schmidt,
WSSA Herbicide Handbook, Weed Science Society of America, 1994 and Supplement 1998.
- Half life in soil:
- Half life in soil:
- Half life in soil:
- Half life in soil:
- Half life in soil:
For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca