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11
Forestry Herbicide Forestry Herbicide Symptoms & Mode of Symptoms & Mode of ActionAction
John BoydUniversity of Arkansas
22
What is mode of action?What is mode of action? How a herbicide disrupts or How a herbicide disrupts or
inhibits normal plant inhibits normal plant development.development.– Examples Examples
cell membrane destruction.cell membrane destruction. block protein synthesisblock protein synthesis interfere with photosynthesisinterfere with photosynthesis
33
Terms to rememberTerms 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) mitosis (cell division)mitosis (cell division)
44
Phloem mobile herbicides move up and down in the plant
Xylem mobile herbicides move up in the plant
Contact herbicides do not move in the plant
Contact
55
Growth Regulator HerbicidesGrowth Regulator Herbicides
FamilyFamily Common NameCommon Name Trade NameTrade Name
PhenoxyPhenoxy 2,4-D2,4-D SeveralSeveral
benzoic acidbenzoic acid dicambadicamba VanquishVanquish
carboxylic acidcarboxylic acid piclorampicloram TordonTordon
carboxylic acidcarboxylic acid triclopyrtriclopyr GarlonGarlon
carboxylic acidcarboxylic acid clopyralidclopyralid TranslineTransline
Affect cell division, cell enlargement, protein Affect cell division, cell enlargement, protein synthesis and respiration. Act by upsetting hormone synthesis and respiration. Act by upsetting hormone balance.balance.
66
Growth Regulator HerbicidesGrowth Regulator Herbicides
Generally applied to leaves, but Generally applied to leaves, but have limited soil activityhave limited soil activity
Length of soil activity is herbicide-Length of soil activity is herbicide-dependentdependent
Highly systemic in susceptible Highly systemic in susceptible plants plants
Activity (pound for pound) varies Activity (pound for pound) varies among herbicidesamong herbicides
Primarily broadleaf activity but Primarily broadleaf activity but may affect grassesmay affect grasses
77
Growth Regulator SymptomsGrowth Regulator Symptoms
Broadleaf plant stem twisting and curlingBroadleaf plant stem twisting and curling Leaves on broadleaf plants exhibit Leaves on broadleaf plants exhibit
cupping, crinkling, strapping, or cupping, crinkling, strapping, or drawstring affectdrawstring affect
Symptoms on grass plants include leaf Symptoms on grass plants include leaf rolling, crinkling, brace root fusion and rolling, crinkling, brace root fusion and malformation. malformation.
Also, flower sterility and missing grain in Also, flower sterility and missing grain in crops.crops.
88
Twisting of stems and leaf cupping are typical symptoms of the growth regulator herbicides.
99Leaf strapping is another typical symptom of these herbicides.
1010
Deformed pin oak leaf caused by 2,4-D. This is referred to as the drawstring effect.
1111Vanquish (dicamba)
untreated
1212
Upward cupping of leaves on azalea. Common symptom with dicamba exposure.
1313
Upward cupping of Upward cupping of leaves on lilac from 2,4-D leaves on lilac from 2,4-D exposure.exposure.
1414
Photosynthesis InhibitorsPhotosynthesis Inhibitors
FamilyFamily Common Common NameName
Trade NameTrade Name
triazinetriazine atrazineatrazine AAtrexAAtrex
triazinetriazine simazinesimazine PrincepPrincep
triazinonetriazinone hexazinonehexazinone VelparVelpar
uraciluracil bromacilbromacil HyvarHyvar
ureaurea diurondiuron KarmexKarmex
ureaurea tebuthiurontebuthiuron SpikeSpikeThese herbicides interrupt photosynthesis the process These herbicides interrupt photosynthesis the process by which green plants convert light energy into food. by which green plants convert light energy into food.
1515
PI’s are Xylem MobilePI’s are Xylem Mobile
Velpar, atrazine, simazine, Spike, Velpar, atrazine, simazine, Spike, HyvarHyvar– Taken up by primarily by roots.Taken up by primarily by roots.– Symptoms appear in older leaves Symptoms appear in older leaves
that are exporting sugarsthat are exporting sugars– Do not move downward when foliar Do not move downward when foliar
applied.applied.
1616
Photosynthesis InhibitorsPhotosynthesis Inhibitors
Most PI’s are soil applied.Most PI’s are soil applied. All PI’s have at least some All PI’s have at least some
postemergence activitypostemergence activity Soil-applied PI’s translocate Soil-applied PI’s translocate
through the xylem.through the xylem.
1717
Interveinal or veinal yellowing Interveinal or veinal yellowing followed by death of plant tissue followed by death of plant tissue from leaf margins inwardfrom leaf margins inward
Postemergence applications Postemergence applications cause rapid burning of plant cause rapid burning of plant tissuetissue
Photosynthesis InhibitorsPhotosynthesis Inhibitors
1818
Princep (simazine)Princep (simazine)
Symptoms often appear on the margins of the oldest leaves (pear).
1919
Karmex (diuron) on oak. Symptoms often appear on the margins of the oldest leaves.
2020
With photosynthesis inhibitors, symptoms start on the margins of the older leaves and move inward.
2121
With photosynthesis inhibitors, symptoms start on the margins of the older leaves and move inward.
2222
Pigment Inhibitor HerbicidesPigment Inhibitor Herbicides
FamilyFamily Common Common NameName
Trade NameTrade Name
isoxazolidinonisoxazolidinonee
clomazoneclomazone CommandCommand
pyridazinonepyridazinone norflurazonnorflurazon SolicamSolicam
not classifieldnot classifield fluridonefluridone SonarSonar
These herbicides cause the green pigments (chlorophyll) These herbicides cause the green pigments (chlorophyll) in plants to be destroyed. Without chlorophyll, plants in plants to be destroyed. Without chlorophyll, plants cannot photosynthesize and will die. cannot photosynthesize and will die.
2323
Pigment inhibitorsPigment inhibitors
Pigment inhibitors cause white leaves Pigment inhibitors cause white leaves in susceptible plantsin susceptible plants
New growth will not contain the green New growth will not contain the green pigments needed for photosynthesispigments needed for photosynthesis
Symptoms may be found on the Symptoms may be found on the cotyledon leaves and true leavescotyledon leaves and true leaves
White growth may be observed within White growth may be observed within veins (primarily with Zorial) and veins (primarily with Zorial) and between veins (primarily with between veins (primarily with Command)Command)
2424
Pigment Inhibitor HerbicidesPigment Inhibitor Herbicides
Zorial (norflurazon).Zorial (norflurazon). Inhibit carotenoid Inhibit carotenoid
formation followed by formation followed by loss of chlorophyll.loss of chlorophyll.
New growth is white, New growth is white, sometimes tinged with sometimes tinged with pink or purple.pink or purple.
Zorial usually follows Zorial usually follows the leaf veins.the leaf veins.
ZorialZorial
2525
Command (clomazone)Command (clomazone)
New growth is New growth is white, white, sometimes sometimes tinged with tinged with pink or pink or purple.purple.
Command: Command: white white between the between the veins.veins. Maple
2626
Root Growth InhibitorsRoot Growth Inhibitors
FamilyFamily Common Common NameName
Trade NameTrade Name
dinitroanilinedinitroaniliness
oryzalinoryzalin SurflanSurflan
dinitroanilinedinitroaniliness
pendimethalipendimethalinn
PendulumPendulum
dinitroanilinedinitroaniliness
prodiamineprodiamine BarricadeBarricadeThe root inhibitors interrupt cell division (mitosis) stopping root growth in seedling plants.
2727
Root Growth InhibitorsRoot Growth Inhibitors Plant death generally occurs before Plant death generally occurs before
emergenceemergence Root inhibitors translocate very littleRoot inhibitors translocate very little Generally stable in upper soil profile Generally stable in upper soil profile Persistence is herbicide-dependentPersistence is herbicide-dependent Most effective on small-seeded grass Most effective on small-seeded grass
and broadleaf weedsand broadleaf weeds
2828
Root Growth InhibitorsRoot Growth Inhibitors
Roots on susceptible plants will be stubby Roots on susceptible plants will be stubby and thick, especially lateral rootsand thick, especially lateral roots
Root limitation may cause stunting of plants Root limitation may cause stunting of plants and phosphorus deficiency symptomsand phosphorus deficiency symptoms
Broadleaf plants may have swollen Broadleaf plants may have swollen hypocotylshypocotyls
Concentration of herbicide at soil surface Concentration of herbicide at soil surface may cause callus tissue to form, leading to may cause callus tissue to form, leading to plant lodgingplant lodging
2929
Roots on susceptible plants will be stubby and thick, especially lateral roots
3030
Cell Membrane DisruptersCell Membrane Disrupters
FamilyFamily Common Common NameName
Trade NameTrade Name
bipyridiliumsbipyridiliums diquatdiquat RewardReward
bipyridiliumsbipyridiliums paraquatparaquat GramoxoneGramoxone
diphenylethediphenylethersrs
lactofenlactofen CobraCobra
Destroy cell membranes, causing cell contents to Destroy cell membranes, causing cell contents to leak out and result in desiccation of plant tissue. leak out and result in desiccation of plant tissue.
3131
Contact herbicidesContact herbicides Do not moveDo not move Herbicides: Paraquat, diquat, Herbicides: Paraquat, diquat,
Cobra (lactofen), MSMACobra (lactofen), MSMA– Rupture cell walls.Rupture cell walls.– Symptoms appear within hours. Symptoms appear within hours.
3232
Cell Membrane Disruptors & Cell Membrane Disruptors & ArsenicalsArsenicals
Rapid yellowing followed by Rapid yellowing followed by desiccation of affected plant tissuedesiccation of affected plant tissue
MSMA, DSMA symptoms generally MSMA, DSMA symptoms generally appear first on leaf tipsappear first on leaf tips
Drift may result in speckled leaf burnDrift may result in speckled leaf burn
3333
Paraquat drift on pecan causes speckling of the leaves.
3434
Organic ArsenicalsOrganic Arsenicals
FamilyFamily Common Common NameName
Trade NameTrade Name
organic organic arsenicalsarsenicals
MSMAMSMA SeveralSeveral
organic organic arsenicalsarsenicals
DSMADSMA SeveralSeveral
Fast acting herbicides that produce rapid leaf burn.
3535
Lipid Synthesis InhibitorsLipid Synthesis Inhibitors(Grass Specific Herbicides)(Grass Specific Herbicides)
FamilyFamily Common NameCommon Name Trade NameTrade Name
cyclohexanedionecyclohexanedione sethoxydimsethoxydim PoastPoast
cyclohexanedionecyclohexanedione clethodimclethodim EnvoyEnvoy
aryloxyphenoxy- aryloxyphenoxy- propionatepropionate
fluazifop-Pfluazifop-P FusiladeFusilade
aryloxyphenoxy- aryloxyphenoxy- propionatepropionate
fenoxaprop-Pfenoxaprop-P Acclaim ExtraAcclaim Extra
These herbicides act by disrupting lipid biosynthesis in These herbicides act by disrupting lipid biosynthesis in grass plants. Plant cells and cellular organelles all contain grass plants. Plant cells and cellular organelles all contain lipid membranes. Therefore, these herbicides affect cell lipid membranes. Therefore, these herbicides affect cell membrane integrity in the meristems.membrane integrity in the meristems.
3636Grass herbicides symptoms on johnsongrass
3737
Grass Specific HerbicidesGrass Specific Herbicides
Initial injury in the meristems occurs Initial injury in the meristems occurs where new leaves are developingwhere new leaves are developing
These regions will turn chlorotic, These regions will turn chlorotic, which is followed by necrosiswhich is followed by necrosis
The affected area will become rotten The affected area will become rotten and will easily separate from rest of and will easily separate from rest of plantplant
Injury will develop slowly (7 to 14 Injury will develop slowly (7 to 14 days)days)
3838
Grass Herbicide SymptomsGrass Herbicide Symptoms
Reddening of leaf tissue.Reddening of leaf tissue. Discoloration of tissue at and above the Discoloration of tissue at and above the
nodes.nodes. Tissue and leaves in the leaf whorl can Tissue and leaves in the leaf whorl can
easily be separated from the rest of the easily be separated from the rest of the plant.plant.
No broadleaf activity.No broadleaf activity.
3939
Amino Acid Synthesis Amino Acid Synthesis InhibitorsInhibitors(ALS inhibitors)(ALS inhibitors)
FamilyFamily Common Common NameName
Trade NamesTrade Names
imidazolinonesimidazolinones imazapyrimazapyr Arsenal, Arsenal, Chopper Chopper StalkerStalker
sulfonylureasulfonylurea metsulfuronmetsulfuron EscortEscort
sulfonylureasulfonylurea sulfometuronsulfometuron OustOustThese herbicides inhibit amino acid synthesis which is These herbicides inhibit amino acid synthesis which is necessary for the formation of plant proteins. necessary for the formation of plant proteins.
4040
ALS CharacteristicsALS Characteristics
Most of these herbicides have soil Most of these herbicides have soil and foliar activity except and foliar activity except glyphosate, and glufosinate glyphosate, and glufosinate
Systemically translocated in Systemically translocated in plantsplants
Soil activity herbicide-dependentSoil activity herbicide-dependent Generally, low use-rate herbicidesGenerally, low use-rate herbicides
4141
ALS SymptomsALS Symptoms
Grass symptoms include: stunting, Grass symptoms include: stunting, purple coloration, and inhibited root purple coloration, and inhibited root systems with bottle-brush appearancesystems with bottle-brush appearance
Broadleaf symptoms include: red or Broadleaf symptoms include: red or purple veins, yellowing of new leaves purple veins, yellowing of new leaves and blackened terminal growthand blackened terminal growth
Glyphosate injury includes initial Glyphosate injury includes initial yellowing followed by death of yellowing followed by death of affected tissueaffected tissue
4242
Amino Acid Synthesis Amino Acid Synthesis InhibitorsInhibitors Accord, Arsenal, Oust, Escort,Accord, Arsenal, Oust, Escort, Move to points of active growth or Move to points of active growth or
food storage.food storage. Affect shoot tips, young buds and Affect shoot tips, young buds and
leaves.leaves. Can cause contact burn and Can cause contact burn and
twisting.twisting.
4343
Arsenal (imazapyr)Arsenal (imazapyr)
Compact growth on azalea
Untreated
4444
Arsenal (imazapyr)Arsenal (imazapyr)
Bunched, compact growth on dogwood and sassafrass
4545
Arsenal symptoms on maple.
4646
Arsenal (imazpyr)Arsenal (imazpyr)
blackberry sweetgum
4747
Amino Acid Synthesis Amino Acid Synthesis InhibitorsInhibitors(Not ALS inhibitors)(Not ALS inhibitors)
FamilyFamily Common Common NameName
Trade NamesTrade Names
Not classifiedNot classified glyphosateglyphosate Accord, Accord, RoundupRoundup
Not classifiedNot classified sulfosatesulfosate TouchdownTouchdown
Not classifiedNot classified glufosinateglufosinate FinaleFinale
4848
Yellowing of new growth is common symptom of glyphosate exposure.
4949
Split bark on apple from Roundup exposure.
5050
Strapped leaves on maple due to Roundup.
5151Roundup drift from the previous fall may cause strapped Roundup drift from the previous fall may cause strapped leaves on peaches, apples and pears the next spring.leaves on peaches, apples and pears the next spring.
5252Stunted, compact growth due to
glyphosate.
5353Finale (glufosinate) on pine
5454Terminal damage from a tank mix of Accord + Arsenal